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Non surgical management of strabismus .ppt
Non- Surgical
Strabismus management
GroupPediatric ophthalmology & Strabismus
Mashhad Eye Research Center
Mashhad University of Medical Sciences
Eye HospitalKhatam
When it comes to treating the patient with strabismus many
ophthalmologists think of surgery first, but there are several
instances where the non-surgical method is best!
Non surgical management of strabismus .ppt
Non surgical management of strabismus .ppt
Non surgical management of strabismus .ppt
Non surgical management of strabismus .ppt
Non surgical management of strabismus .ppt
What is the prescription aim?
Our purpose is best visual acuity in distance
versus binocular alignment
 Certainly ,we want to eliminate any amblyogenic
factors by using the optical correction and consider
the binocular status
Non surgical management of strabismus .ppt
Prescribing for Children
• In adults, the correction of refractive errors has one
measurable endpoint: the best corrected visual
acuity.
• Prescribing visual correction for children often has
two goals:
1- providing a focused retinal image
2- achieving the optimal balance between accommodation and
convergence.
spectacle
Create sharp retinal image that
improve fusion
Assist balance between accomodation
and convergence
Trend is prescribe full amount of
refractive error in cycloplagia
Young children normally accept the
correct glass
General Rules
Search for hurt behind nose or pinch the
nose or uncomfortable frame
Atropinization of both eyes for 3 to 4 days in
case with unable to relax accomodation
Explain indication in the presence of normal
vision(refractive accomodative ET)
Consider full corection from infancy through
pre school age
spectacle
Consider prescibe BCVA in
old children
Hypermetropic correction
greater than +2 in
esotropic patient
spectacle
case1
5 years old girl referred to clinic for strabismus.
Vision: BCVA: OD:20/20,OS:20/30
Refraction:OD:+1 sph,os:+2 sph
EOM:10ET with glass(far),30ET with glass(near)
Fundus: normal
What is your plan?
GlassBifocal
Valuable in high AC/A ratio accomodative ET
Restricted in whom that were orthotropic or
small angle ET in far by FCR but residual ET at
near that convert to orthotropia or esophoria by
additional plus lens
Contraindication is amblyopia and not complete
elimination of ET in near
Start with +1 sph and increase power in step
of +0.5 up to +3 sph
Minimal power that convert ET to E
prescribed(prevent excessive relaxation of
accommodation)
Success depend on proper bifocal segment
Prefer straight top segment which bisect pupil
or touch lower border in straight head position
GlassBifocal
Non surgical management of strabismus .ppt
Non surgical management of strabismus .ppt
Progressive as a substitute
Fusional amplitude increase so reduce power
stepwise until discontinue
If still depend to maintain fusion during
teenage year consider surgery
FCR must be done semiannually and correction
readjusted
Goal is maximal hyperopic correction but
reduce bifocal power by same amount if
additional plus is necessary
GlassBifocal
High AC/A Ratio
 Any uncorrected hyperopic refractive error will
trigger convergenece , therefore 0.50 D ,should be full
corrected
 It may be possible to avoid bifocal by simply slightly
overplussing the patient with a single vision
correction ( +0.50 +0.75D )
 Bifocal strength +2 +3.5 D
 Bifocal are often eliminated in the teenage years
 6years old boy referred to strabismus clinic due to
deviation.parents notice occasional outward deviation
of eyes especially after awakening.
 Vision:10/10 (o.u)
 Refraction:-1.00 (o.u)
 EOM:15 prism diopter X(near),25 prism diopter XT(far)
 Fundus:normal What is your plan?
case2
Aim of IXT treatment
Reducing episodes of manifest
exotropia
Facilitating sensory fusion and achieving constant
binocular alignment and normal stereoacuity.
Nonsurgical management is indicated
In patients with excellent control as
measured by normal distance stereoacuity
In young children who are at risk of developing
monofixational esotropia from persistent
surgical overcorrection
In children
By maintaining the
potential for equal
vision in each eye and
preserving binocular
fusion status.
Nonsurgical techniques
such as minus lenses and
prisms can prevent or
reverse early sensory
anomalies
Refractive Errors
• Unequal clarity in vision represents an obstacle to
fusion and can facilitate suppression, contributing to
progressive loss of control in X(T).
• Significant RE, especially astigmatism and
anisometropia, need to be corrected.
• All patients in minus lenses should be seen within
3 to 4 weeks after starting the therapy.
• Minus lenses should be discontinued if esotropia
develops.
• There are studies that suggest that this treatment
may induce myopia
• As the child grows older, asthenopic symptoms
with over-minus lenses become prominent as the
amount of near work increases
• Part time patching of the non-deviating eye for four to six
hours daily may convert an intermittent exotropia to a
phoria.
• Although the benefit is usually temporary, occlusion can be
used to postpone surgical intervention in responsive patients
• Alternate occlusion may be used in patients with equal
fixation preferences
• Initially the results are evaluated after 4 months of occlusion.
• If the angle of deviation is decreased the occlusion should be
continued and assessment made every 4 months until no
further change occurs.
• In case there is no improvement for 4 months, it is
discontinued
Occlusion
Various Non-Surgical Therapies
for Intermittent Exotropia
Corrective lenses for any significant RE
part time Alternate Occlusion
Minus lenses Therapy
Orthoptics (Including
Convergence exercises)
Therapeutic Base – in
prisms
Botulinum
Toxin
Indications for Surgery
Once deterioration is
documented
Waiting until deterioration
has relentlessly progressed
may reduce the chance of
obtaining an excellent
surgical outcome
So improving fusional states accompanied by
higher surgical success rate
The AAO PPP pediatric glass prescribing
guideline
• When hyperopia and esotropia coexist, initial
management includes full correction of the
cycloplegic refractive error.
• Later, reductions in the amount of correction may
be appropriate, based on the amount of esotropia
and level of stereopsis at near and at distance with
the full cycloplegic correction in place
Hyperopia associated with partly
of full accommodative esotropia
 When hyperopia is associated with overt esotropia or ever
large esophoria , a full cycloplegic correction should be
prescribed
 The principle is to prescribed the maximum plus the patient
will accept without degrading the visual acuity
 Generally this equals the full cyclopentolate or atropine
refration upto the age 2 years because the patients
enviroment is close at hand and subjective tests are not
possible
 In older children 0.50 – 1.00 D should be subtracted
 In some cases of acc /ET an extra + 0.50 D could make
some difference to the strabismus
Undercorrection &
overcorrection
Undercorrect myopia in accommodative
ET rarely tolerated
Slight overcorrection of myopia in IXT
Optical overcorrection or under
correction in treatment of
amblyopia(penalization)
Non surgical management of strabismus .ppt


Non surgical management of strabismus .ppt
Non surgical management of strabismus .ppt
Non surgical management of strabismus .ppt
Ophthalmic Prism
Ali Akbar Sabermoghaddam
Associated professor of
Ophthalmology
Eye research center &
Khatam eye hospital, MUMS
Non surgical management of strabismus .ppt
Non surgical management of strabismus .ppt
Non surgical management of strabismus .ppt
Prisms bend rays toward the
base.
PRISMS
P
cm displacement
1 m
=
Prismatic Power (P )
apex
base
100
cm
X cm
Ophthalmic Prism
Prismatic power
Ophthalmic
Prism
• Prisms function by
bending rays of light
towards the base of
the prism.
• The degree of bending
of light depends upon
the angle of
incidence of light and
the prismatic power.
Non surgical management of strabismus .ppt
Ophthalmic prisms have
been used in the treatment
of binocular problems for
more than 100 years.
Ophthalmic Prism
Corrective Prism:
1. Ground – In Prism.
2. Fresnel – On Prism (Press-on Prisms).
Ophthalmic Prism
PRESCRIBING INDUCED PRISM BY INTENTIONALLY DISPLACING THE
OPTICAL CENTERS
 Light traveling through the optical center of a lens encounters no
prismatic power and passes through undeviated.
 However, as the distance from the optical center increases,
increasing prismatic power is encountered.
 Prentice's rule : This is defined algebraically using the formula:
Δ = hD where Δ = prism diopters , h = distance from the optical
center in centimeters, and D= power of the lens in diopters.
 Of note, the direction of displacement of light depends on
whether the lens is of minus or plus power :
- Minus lenses function as prisms held apex to apex; that is, as if
the apex
of the prism were at the optical center of the lens.
- In other words, a ray of light traveling above the optical
center
encounters base-up prism power, and a ray traveling below
the optical
center encounters base-down prism.
 In the mid 1960's, the 150-year-old Fresnel principle
was applied to ophthalmic prisms for the first time.
The first ophthalmic Fresnel prism, known as the
"wafer" prism, was molded of an acrylic resin,
making it much lighter and thinner than the
corresponding powers of conventional prisms, thus
extending the useful range of prism powers.
 In 1970, the Press-OnTM prism, a Fresnel-principle
prism molded in flexible plastic, was introduced to
ophthalmologists. This thin, light membrane prism
had the advantage of conforming and adhering to
a smooth surface and thus could be affixed directly
to a plano or basecurved correcting spectacle
lens.
Non surgical management of strabismus .ppt
Non surgical management of strabismus .ppt
Non surgical management of strabismus .ppt
Ophthalmic Prism
Fresnel – On Prism
• Fresnel prisms are constructed as a series of very narrow adjacent
prisms on a thin sheet of plastic.
• The prism is flexible, enabling it to conform to the base curve of the
spectacle lens.
• The commercially available powers of Fresnel prisms (in increments
of 1 from 1 to 10, a power of 12, and in increments of 5 from 15 to
40).
Non surgical management of strabismus .ppt
Non surgical management of strabismus .ppt
Non surgical management of strabismus .ppt
Internal Reflection
Color Separation
Magnification
Visual acuity
Fusion and stereopsis
Ophthalmic Prism
FRESNEL PRISMS
 The prism is applied by pressing the smooth surface
of the prism against the back surface of the
spectacle lens while the lens is submerged in water.
 Disadvantage of Fresnel prisms is that higher-power
:
- Introduce glare and chromatic aberration.
- Significant decline in vision.
- Minimal decline in visual acuity when using
Fresnel prisms
of 12 prism diopters or less
Ophthalmic Prism
Terminology
a. Relieving Prism.
• Action – Reduces the demand for controlling
fusional vergence
b. Inverse Prism.
• Action – Increases the demand for controlling
fusional vergence
c. Yoked Prism
• Action – Directs the eyes into a specific gaze
direction
d. Sector / Regional Prism
• Action – Reduces the demand for controlling
vergence in more than 1 gaze
Ophthalmic Prism
Indication :
1- Strabismus :
- Comitant.
- Non - Comitant (Diplopia) .
2 - Symptomatic heterophorias : Convergence
training for exodeviation.
3 – presbyopia with symptomatic CI
4 - Nystagmus
5- Amblyopia
6- Cosmetic
Ophthalmic Prism
Prism For Deviations :
1. Exo: Base-In (BI) over either eye
2. Eso : Base-Out (BO) over either eye
3. RHT:
- Base-Down (BD) over right eye
- Base-Up (BU) over left eye
4. LHT :
- BD over left eye
- BU over right eye
Ophthalmic Prism
Prism For Head postures :
1. Left face turn Yoked prism
base left
2. Right face turn Yoked prism base
right
3. Chin elevation Yoked prism (BU)
4. Chin depression Yoked prism(BD)
Chin Depression
Yoked prism(BD)
Ophthalmic Prism
Adverse ( Reverse) Prism Indications
:
1.To ignore the diplopic image
2.During convergence training for
exodeviation: (BO Prism)
3.Cosmetics for patients who has very
poor acuity in one eye or are poor
surgical candidates (approximately
15 prescribed
4.Strengthening of the weak muscle
1- Strengthening of the weak muscle
2- Prevent Contractures of antagonist
Adverse Prism
Inoperable strabismus :
Adverse Prism
Cosmetic:
Relieving Prism
 In order to move the image to where the eye is
looking, thus restoring fixation and binocular vision:
For diplopia
 Base of the prism is placed over the weak (or
paralyzed muscles)
Relieving Prism
Surgical over and under-correction:
Relieving Prism
Mild Amblyopia :
Relieving Prism
Nystagmus :
Relieving Prism
DIPLOPIA :
Nerve palsies
DIPLOPIA
Myasthenia Gravis, Multiple
Sclerosis , Graves Disease
OBLIQUE PRISMS :
DIPLOPIA
RHT
Symptomatic Heterophoria:
Prismatic correction of exophoria
Relieving Prism
Prism for Symptomatic
Heterophoria
Prism for Symptomatic
Heterophoria
sheard’s criterion :
Formula: prism needed=2/3 (phoria) –
1/3 (compensating fusional vergence)
If a patient has 6 exophoria and
base-out prism (BO) to blure is 6:
2/3 X6 -1/3X6=2  you would
prescribe 2  base-in for this patient
Non surgical management of strabismus .ppt
Prism for Other Medical
- Bed-ridden patients.
- Ankylosing spondylitis ,
- Other postural deformities.
Ophthalmic Prism
CLINICAL APPLICATIONS
 In patients with tropias (small, comitant deviations) .
 To ease asthenopia in patients with phorias.
 Small-angle strabismus following intraocular surgery and
 Residual deviations following strabismus surgery.
 In most cases of superior oblique palsy, many patients will
respond well to a small amount of vertical prism, with
improvement in double vision and in head tilt as well.
 Intermittent exotropia (to partially correct the angle of
misalignment and decrease the fusional convergence
requirement),
 convergence insufficiency (best used with separate reading
glasses to avoid introducing esotropia at distance),
 divergence insufficiency (best used at distance only),
 Anisometropia in the reading position (best treated with …
Ophthalmic Prism
OTHER CLINICAL USES OF PRISM
 Prisms have been incorporated into contact lenses as a
means of correcting vertical diplopia, but this method is only
rarely used.
 In some cases, prisms may be prescribed as a form of eye
‘exercise’, For example, in convergence insufficiency, the
patient might be prescribed base out prism over both eyes
to increase the exotropia at near.
 This is typically provided as a removable Fresnel prism that is
worn part of the day, with the goal of making the patient
more comfortable the rest of the day when the prism is not
worn.
 Prisms may be used in the setting of nystagmus to improve
head positions and to improve acuity.[To correct head
positions, prisms are ‘yoked’ to shift the image into the null
zone area. For example, a patient who has a right head turn
and a null point in left gaze would be treated with base-out
How to Prescribe a Prism for Combined
Vertical and Horizontal Strabismus
OBLIQUE PRISMS
The Procedure
 Estimating prism power. A good way to arrive at a starting
prism power is to take the higher power prism measurement
and add one-half of the lower power measurement.
 For example, take a hypothetical patient with 20 prism diopters
of esotropia and 10 PD of left hypertropia. The higher power
measurement (20) is added to half the lower power
measurement (10 ÷ 2 = 5). Therefore, a 25-PD handheld prism is
selected.
 Testing the prism. This prism is then placed before the
nondominant eye. Assuming the left eye is nondominant, the
25-PD handheld prism would be placed with the base out and
slightly down in front of the left eye to correct the combined
esotropia and left hypertropia.
 This prism is rotated slowly clockwise or counter-clockwise until
the patient notes that the two images are fused.
How to Prescribe a Prism for Combined Vertical and
Horizontal Strabismus
OBLIQUE PRISMS
The Procedure
 If the patient is unable to fuse, another prism is selected (start
with a prism one increment higher or lower—in this case either
a 30-PD or 20-PD and the process is repeated until fusion
occurs.
 Prescribing the prism. A wax pencil is then used to draw a line
directly on the outside of the spectacles, using the base of the
handheld prism as a guide. The clinician writes a prescription
that includes the prism power and a statement regarding the
orientation of the prism. For the above example, the
prescription would read: ―25-PD Fresnel prism base out and
down as marked.
Ophthalmic Prism
OBLIQUE PRISMS
 Oblique prisms are required when trying to prescribe a single
Fresnel prism for a combined vertical and horizontal deviation.
Vector addition is used to combine horizontal and vertical prism.
For example, combining 5 Δ base up with 5 Δ base out may be
solved using the Pythagorean theorem (for a right triangle with
sides a, b, andc, with c the hypotenuse, a2 + b2 = c2). In this
case, 52 + 52 = c2 = 50; so, c = √50. Thus, 7.1 Δ of Fresnel prism
may be prescribed base up and out in the 45° meridian. More
complex combinations of vertical and horizontal prisms may be
determined by applying basic trigonometric relationships of right
triangles, or more practically by measuring the combination of
vertical and horizontal prism in the lensmeter. When prescribing
a combination of vertical and horizontal prism for ground-in
prism, these calculations are not necessary, as most opticians
prefer to be given the horizontal and vertical components
separately.
OBLIQUE PRISMS
How to Prescribe a Prism for Combined
Vertical and Horizontal Strabismus
OBLIQUE PRISMS
CASE ONE: A 75-year-old woman with Graves disease
complained of diplopia.
 Motility testing showed 25 PD of left hypertropia and 10 PD of
esotropia.
 A 30-PD handheld prism was chosen (25 + half of 10),
 Held base down and out in front of the nondominant left eye.
 The prism was rotated slightly clockwise and counter-
clockwise until fusion occurred.
 The outside of the glasses were marked with a wax pencil
along the base of the prism.
 An optician applied a 30-PD Fresnel prism with the base
oriented as marked. The prism relieved the diplopia in primary
gaze.
How to Prescribe a Prism for Combined Vertical
and Horizontal Strabismus
(OBLIQUE PRISMS)
CASE TWO: A 52-year-old woman developed incomitant
strabismus with binocular oblique diplopia following an
embolization procedure for a dural arteriovenous fistula.
 Motility testing showed 10 PD of exotropia and 8 PD of left
hypotropia in primary gaze.
 A 15-PD handheld prism was chosen (10 + half of 8, rounded
off to the closest available Fresnel prism power), held base in
and up in front of the left eye,
 Then rotated in a manner similar to that described above until
fusion occurred.
 The glasses were marked with a wax pencil.
 The patient took the marked glasses to an optician for
application of a 15-PD Fresnel prism, base in and up to the left
spectacle lens.
 The prism corrected the diplopia in primary gaze.
Non surgical management of strabismus .ppt
Ophthalmic Prism
SLAB-OFF PRISM
 Patients who have anisometropia may suffer from diplopia or
asthenopia when the line of sight does not pass through the
optical centers of their spectacles.
 This occurs because the displacement induces a net prismatic
effect.
 In general, most patients are able to use fusional abilities to
adapt to the induced horizontal prism.
 However, vertical gaze is often quite problematic. For example, a
patient who has a refractive error of –3.00 OD and +1.00 OS will
have induced prism when looking away from the optical center.
If this patient looks 1 cm below the optical centers to read, the
induced prismatic power will be 3Δ (1 cm ×3 D) of base-down
prism on the right and 1Δ (1 cm ×1 D) of base-up prism on the left,
giving a net prismatic effect of 4Δ base down on the right (base
up on the left). Cover testing would reveal a 4Δ left hypertropia in
the reading position.
 There are several options for treating the vertical prismatic effects
Ophthalmic Prism
MEASURING PRISM IN SPECTACLES
 The effective prism power in spectacle lenses is the
combination of ground-in prism plus prism induced by
displacement of the optical centers. To measure the amount
of effective prism in spectacles, ask the patient to fixate on
your own eye, then mark the point where line of sight
intersects the lens using a felt tip marker. (The line of sight is the
line connecting the object of regard with the center of the
pupil.) The prism power at this location is the effective prism
power. (This may or may not be the intended prism power
depending on whether or not the optician correctly placed
the optical center of the lens in front of the patient's pupil.) The
glasses are then positioned on the lensmeter such that the
mark on the lens is centered within the lensmeter port. If no
prism is present, the mires representing the two cylindrical axes
will intersect in the center of the lensmeter reticle. If prism is
Ophthalmic Prism
WRITING A PRISM PRESCRIPTION
 When prescribing prisms, it is important to specify the amount
and direction of the prism in addition to the lens or lenses into
which the prism should be incorporated. Fresnel prisms are
useful as a trial before grinding the prism into the spectacle
lens. In our experience, it is best if Fresnel prisms are placed in
the office or by a trusted optician; errors in positioning are
frequent when the prisms are placed by inexperienced
individuals.
 Prescriptions requiring prism must be written with special care
to avoid errors. It is advisable to communicate directly with the
optician for particularly complex prescriptions. For combined
vertical and horizontal deviations requiring oblique Fresnel
prisms, the axis of the base must be specified using degrees as
for astigmatic lenses. However, the astigmatic axis allows for
two positions of the base; that is, ‘10Δ base 30°’ could be
interpreted as ‘10Δ base up-and-out in the 30° meridian’, oras
‘10Δ base down-and-in
Non surgical management of strabismus .ppt
 Indication
- Comitant Strabismus
- Non - Comitant Strabismus (Diplopia) :
- Eliminate abnormal head position
- Provide single binocular vision
- Symptomatic heterophorias .
- Abnormal head postures.
- Nystagmus.
• In a patient with a long-standing paresis, what are the
considerations when prescribing prism?
• In a patient with a recent onset paresis, what are the
considerations when prescribing prism?
• How do you prescribe prism using Sheard’s criterion?
• How do you prescribe prism using Caloroso’s Residual
Vergence Demand Criterion?
Terminology
a. Corrective or Neutralizing Prism:
• Goal – To stabilize normal sensory fusion
• Prism Action – Neutralizes the demand for controlling
fusional
vergence
b. Relieving Prism:
• Goal – To stabilize sensorimotor fusion
• Action – Reduces the demand for controlling fusional
vergence
c. Overcorrective Prism:
• Goal – To disrupt anomalous correspondence
• Action – Reverses the demand for controlling fusional
vergence
Terminology
d. Inverse Prism for Training or Disruptive Prism Therapy:
• Goal – To increase fusional vergence ability
• Action – Increases the demand for controlling fusional
vergence
e. Inverse Prism for Cosmesis:
• Goal – To enhance cosmesis of a strabismus when a
patient has poor treatment prognosis
• Action – Optically displaces the image of the eyes in a
direction opposite the strabismus when an observer views the
patient.
f. Yoked Prism:
• Goal – To stabilize bv in non-concomitancy or dampen
nystagmus
• Action – Directs the eyes into a specific gaze direction
g. Sector / Regional Prism:
• Goal – To stabilize binocular vision in one or more gaze
positions
• Action – Reduces the demand for controlling vergence in
more than 1 gaze
Non surgical management of strabismus .ppt
Non surgical management of strabismus .ppt
4. Constant Strabismus
 a. Corrective Prisms for Resolvable Strabismus
 • Avoid using prism when patient has Anomalous
Correspondence, peripheral suppression,
amblyopia.
 • Must have normal correspondence and normal
peripheral sensory fusion
 • Monitor for prism adaptation. Can use temporary
Fresnel prisms.
 • Once normal sensory fusion achieved for 3-6
months (can be less for infants)
 - Titrate prism 2-4Δ at a time
 3M Press-On™ Optics
 AVAILABLE PRISMS and ASPHERIC LENSES PRISMS ASPERIC -
PLUS ASPERIC - MINUS ASPERIC - D-SEGS
 Diopter Power Power Power
 1.0 􀁕 + .5 -1.0 1.0
 2.0 􀁕 +1.0 -2.0 1.5
 3.0 􀁕 +1.5 -3.0 2.0
 4.0 􀁕 +2.0 -4.0 2.5
 5.0 􀁕 +2.5 -5.0 3.0
 6.0 􀁕 +3.0 -6.0 4.0
 7.0 􀁕 +3.5 -7.0 5.0
 8.0 􀁕 +4.0 -8.0 6.0
 9.0 􀁕 +5.0 -9.0
 10.0 􀁕 +6.0 -10.0
 12.0 􀁕 +7.0 -11.0
 15.0 􀁕 +8.0 -12.0
 20.0 􀁕 +10.0 -13.0
 25.0 􀁕 +12.0 -14.0
 30.0 􀁕 +14.0
 35.0 􀁕 +16.0
 40.0 􀁕
Non surgical management of strabismus .ppt
Non surgical management of strabismus .ppt
Conditio
n
Relevant
Issues
Function of
3M Press-
On prism
Suggested use of 3M Press-on Prisms
STRABISMUS
Early
onset
strabism
s
Surgical over
and under-
correction is a
common
problem
Preoperative
prism
adaptation
enhances
surgical
outcome or
establishes
fusion
nonsurgically.
To obtain
presurgical
fusion without
weight,
thickness, and
incoveniene of
conventional
prisms
To provide a
fusion lock and
stability for
post-surgical
residual
deviations.
Condition Relevant
Issues
Function of
3M Press-
On prism
Suggested use of 3M Press-on Prisms
STRABISMUS
Mild
Amblyopia
Requires early
intervention
to avoid
progression
Applied over
the preferred
eye as a weak
patch
Small image
degradation
of prism
serves as
weak
occluder
Prisms blurs
visual acuity
in dominant
eye
Condition Relevant
Issues
Function of
3M Press-
On prism
Suggested use of 3M Press-on Prisms
STRABISMUS
Nystagmus Can allow
patient to
assume a
more normal
head position
to find the
null point of
the
nystagmus
Prisms with
the base away
from the
direction gaze
preference
can allow the
eyes to rotate
into position
without a
large head
turn
Redirects the
visual gaze
toward the
fireld of
minimal
tremor
Requires
placement of
prisms over
both lenses.
In absence of
strabismus
,the power
needs to be
matched.
Condition Relevant
Issues
Function of
3M Press-
On prism
Suggested use of 3M Press-on Prisms
STRABISMUS
Inoperable
strabismus
Fragile health
or patient
concerns may
delay or
preclude
surgery
Provides
cosmetic
improvement
by shifting the
apparent
position of
the eye in a
desirable
direction
For cosmetic
improvement
of certain
tropias with
an inverse
prism applied
before the
deviating eye
(e.g.,base-in
prism for
esotropia).
For constant
tropias where
surgery is not
contemplated
and binocualr
fusion is not
possilbe
Cosmesis
Condition Relevant
Issues
Function of
3M Press-
On prism
Suggested use of 3M Press-on Prisms
DIPLOPIA Associated with several health issues, I.e. including mechanical restrictions,
neurologic disorders (nerve palsies), poststroke skew deviation, postretinal
detachment,scleral buckles, thyroid ophthamology , injuries such as
blowout fractures and brain injuries
3th, 4th ,
and 6th
nerve
palsies
May recover
with time
Allows
binocularity
during
recovery
period. May
be changed
as muscle
function
returnes.
To eliminate
diplopia
resulting
from recent-
onnset
strabismus
(e.g.stroke,
ocualr
muscles
paresis
systemic
disease)
Condition Relevant
Issues
Function of
3M Press-
On prism
Suggested use of 3M Press-on Prisms
DIPLOPIA Associated with several health issues, I.e. including mechanical
restrictions, neurologic disorders (nerve palsies), poststroke skew
deviation, postretinal detachment,scleral buckles, thyroid
ophthamology , injuries such as blowout fractures and brain
injuries
Incomitant
strabismus
Deviation
varies with
gaze
direction0
Applied over
part of a lens
at allow
correction in
specific gaze
positions.
For
incomitant
strabismus,
which
demands
different
prism power
in certain
fields of gaze
Prisms can
be easily cut
and placed
on spectacles
for
correction
where
needed
Condition Relevant
Issues
Function of
3M Press-
On prism
Suggested use of 3M Press-on Prisms
PHORIAS
Symptomatic
or
Decompensate
d phorias
Fusion
disruption
causes eyes to
deviate
Promotes,
fusion reduces
deviation
For
symptomatic
phorias with
different
distance and
near angles,
apply prism to
upper and/or
lower portions
of spectacle
lenses
Condition Relevant Issues Function of 3M
Press-On prism
Suggested use of 3M Press-on
Prisms
Other Medical Indications for Press-On prisms
Bed-ridden
patients
Cannot elevate
head to read or
watch television
Based-down
prisms on both
lenses change
image’s angle
Apply 30* prism
base down to
each spectacle
lenses
Ankylosing
spondylitis other
postural
deformities
Limited head
movement
Prisms change
image’s angle
Apply prism base
up to spectacle
lens
Non surgical management of strabismus .ppt
case1
 A 45 years- old man who had car accident two week
ago came with intractable diplopia .
 Vision: 20/20(o.u)
 Motility: 40 prism diopter ET with limitation of
abduction(-4) in right eye.
 Fundus: normal.
What is your
management
case2
 15 years old boy referred to strabismus clinic for
deviation. He had occasional deviation especially after
illness and complain of asthenopia.
 BCVA:OU:20/20
 Refraction:-0.5sph(OU)
 EOM:10 prism diopterX(far),2o prism diopterX (near)
 Fundus: normal
What is your plan?What is your
plan?
Non surgical management of strabismus .ppt
Non surgical management of strabismus .ppt
Non surgical management of strabismus .ppt
Non surgical management of strabismus .ppt
Other indication
 Fourth Nerve Paresis
 Accommodative Esotropia
 Acquired Esotropia
 Intermittent Exotropia
 Multiply Operated Strabismus
 Thyroid Ophthalmopathy
 Nystagmus
Sixth Nerve Paralysis
 Acute cases of any age or origin are followed without
treatment for 3 to 4 weeks
 If healing begins within a month it typically will be
progressive and complete
 After 1 month, if disabling diplopia persists and
recovery is not progressing, or if a child remains
esotropic in all gaze positions so that binocularity is
threatened, then injecting the medial rectus (MR) on
the affected side(s) is appropriate
 for diabetic patients who have a generally good
prognosis, the value of botulinum toxin treatment lies
in earlier rehabilitation.
 botulinum toxin to release MR contracture makes it
appropriate to wait a full 6 months after the onset
before transposition surgery
 Injection several months after surgery has corrected
several undercorrected transposition cases and may
need to be repeated.
Non surgical management of strabismus .ppt
Infantile Esotropia
 Simultaneous bimedial toxin injection is quite
successful
 All reports include 2 years or more of follow-up and
show high correction rates of 60% to 80% with
multiple injections
 Perform simultaneous bimedial injection
 Inject as early as age 3 months.
 Repeats simultaneous bimedial injection with
recurrence of esotropia exceeding 15 PD
Non surgical management of strabismus .ppt
Non surgical management of strabismus .ppt
Side effect
 Ptosis
 Induced vertical deviation
 Hemorrhage
 Pupillary dilation
 Globe perforation
Non surgical management of strabismus .ppt
orthoptics
 Goal is give comfortable binocular vision
 used to combat suppression,amblyopia,ARC,enhance
fusional amplitude and improve stereopsis
 In successful case transform tropia to phoria but not
eliminate it
 Supervision and direction of treatment responsibility
of ophthalmologist
Application
 Convergence insufficiency
 Fusion training
 Antisuppression training
 ARC
Convergence insufficiency
 Most effective treatment
 Converge on an approaching object such as pencil or a
light while red filter is placed over one eye
 Aware of physiologic diplopia of a distant object while
fixing on a target at near
 Training fusional convergence with base out prism or
major amblyoscope
 Base out prism used during reading and continue on
home with increasing power
Fusion training
 Training of fusion amplitude enable symptomatic
heterophoria patient more comfortable
 Done by major amblyoscope or prism exercise
Antisuppression Training
 Orthoptic is aimed to awareness of physiologic
diplopia in heterophoria and diplopia in heterotropia
 Once diplopia elicited vergence control activated
 Forcing suppressed area concurrently with
corresponding area of dominant eye
 Stimulation of retina of deviated eye by moving visual
target on major amblyoscope back and forth across
suppression scotoma
 Suppression cannot be effectively eliminated by
orthoptic
ARC
 Treatment is no longer practiced
 The methods that were used are historical and
theoretic
 Based on principle that if the image of the fixation
point is moved with the amblyoscope over the retina of
the deviated eye anomalous localization of the double
image may suddenly be replaced by normal
localization
 ARC had benefit in preserving advantage of normal
binocular vision so do not treat it

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Non surgical management of strabismus .ppt

  • 2. Non- Surgical Strabismus management GroupPediatric ophthalmology & Strabismus Mashhad Eye Research Center Mashhad University of Medical Sciences Eye HospitalKhatam
  • 3. When it comes to treating the patient with strabismus many ophthalmologists think of surgery first, but there are several instances where the non-surgical method is best!
  • 9. What is the prescription aim? Our purpose is best visual acuity in distance versus binocular alignment  Certainly ,we want to eliminate any amblyogenic factors by using the optical correction and consider the binocular status
  • 11. Prescribing for Children • In adults, the correction of refractive errors has one measurable endpoint: the best corrected visual acuity. • Prescribing visual correction for children often has two goals: 1- providing a focused retinal image 2- achieving the optimal balance between accommodation and convergence.
  • 12. spectacle Create sharp retinal image that improve fusion Assist balance between accomodation and convergence Trend is prescribe full amount of refractive error in cycloplagia Young children normally accept the correct glass General Rules
  • 13. Search for hurt behind nose or pinch the nose or uncomfortable frame Atropinization of both eyes for 3 to 4 days in case with unable to relax accomodation Explain indication in the presence of normal vision(refractive accomodative ET) Consider full corection from infancy through pre school age spectacle
  • 14. Consider prescibe BCVA in old children Hypermetropic correction greater than +2 in esotropic patient spectacle
  • 15. case1 5 years old girl referred to clinic for strabismus. Vision: BCVA: OD:20/20,OS:20/30 Refraction:OD:+1 sph,os:+2 sph EOM:10ET with glass(far),30ET with glass(near) Fundus: normal What is your plan?
  • 16. GlassBifocal Valuable in high AC/A ratio accomodative ET Restricted in whom that were orthotropic or small angle ET in far by FCR but residual ET at near that convert to orthotropia or esophoria by additional plus lens Contraindication is amblyopia and not complete elimination of ET in near
  • 17. Start with +1 sph and increase power in step of +0.5 up to +3 sph Minimal power that convert ET to E prescribed(prevent excessive relaxation of accommodation) Success depend on proper bifocal segment Prefer straight top segment which bisect pupil or touch lower border in straight head position GlassBifocal
  • 20. Progressive as a substitute Fusional amplitude increase so reduce power stepwise until discontinue If still depend to maintain fusion during teenage year consider surgery FCR must be done semiannually and correction readjusted Goal is maximal hyperopic correction but reduce bifocal power by same amount if additional plus is necessary GlassBifocal
  • 21. High AC/A Ratio  Any uncorrected hyperopic refractive error will trigger convergenece , therefore 0.50 D ,should be full corrected  It may be possible to avoid bifocal by simply slightly overplussing the patient with a single vision correction ( +0.50 +0.75D )  Bifocal strength +2 +3.5 D  Bifocal are often eliminated in the teenage years
  • 22.  6years old boy referred to strabismus clinic due to deviation.parents notice occasional outward deviation of eyes especially after awakening.  Vision:10/10 (o.u)  Refraction:-1.00 (o.u)  EOM:15 prism diopter X(near),25 prism diopter XT(far)  Fundus:normal What is your plan? case2
  • 23. Aim of IXT treatment Reducing episodes of manifest exotropia Facilitating sensory fusion and achieving constant binocular alignment and normal stereoacuity.
  • 24. Nonsurgical management is indicated In patients with excellent control as measured by normal distance stereoacuity In young children who are at risk of developing monofixational esotropia from persistent surgical overcorrection
  • 25. In children By maintaining the potential for equal vision in each eye and preserving binocular fusion status. Nonsurgical techniques such as minus lenses and prisms can prevent or reverse early sensory anomalies
  • 26. Refractive Errors • Unequal clarity in vision represents an obstacle to fusion and can facilitate suppression, contributing to progressive loss of control in X(T). • Significant RE, especially astigmatism and anisometropia, need to be corrected.
  • 27. • All patients in minus lenses should be seen within 3 to 4 weeks after starting the therapy. • Minus lenses should be discontinued if esotropia develops. • There are studies that suggest that this treatment may induce myopia • As the child grows older, asthenopic symptoms with over-minus lenses become prominent as the amount of near work increases
  • 28. • Part time patching of the non-deviating eye for four to six hours daily may convert an intermittent exotropia to a phoria. • Although the benefit is usually temporary, occlusion can be used to postpone surgical intervention in responsive patients • Alternate occlusion may be used in patients with equal fixation preferences • Initially the results are evaluated after 4 months of occlusion. • If the angle of deviation is decreased the occlusion should be continued and assessment made every 4 months until no further change occurs. • In case there is no improvement for 4 months, it is discontinued Occlusion
  • 29. Various Non-Surgical Therapies for Intermittent Exotropia Corrective lenses for any significant RE part time Alternate Occlusion Minus lenses Therapy Orthoptics (Including Convergence exercises) Therapeutic Base – in prisms Botulinum Toxin
  • 30. Indications for Surgery Once deterioration is documented Waiting until deterioration has relentlessly progressed may reduce the chance of obtaining an excellent surgical outcome So improving fusional states accompanied by higher surgical success rate
  • 31. The AAO PPP pediatric glass prescribing guideline
  • 32. • When hyperopia and esotropia coexist, initial management includes full correction of the cycloplegic refractive error. • Later, reductions in the amount of correction may be appropriate, based on the amount of esotropia and level of stereopsis at near and at distance with the full cycloplegic correction in place
  • 33. Hyperopia associated with partly of full accommodative esotropia  When hyperopia is associated with overt esotropia or ever large esophoria , a full cycloplegic correction should be prescribed  The principle is to prescribed the maximum plus the patient will accept without degrading the visual acuity  Generally this equals the full cyclopentolate or atropine refration upto the age 2 years because the patients enviroment is close at hand and subjective tests are not possible  In older children 0.50 – 1.00 D should be subtracted  In some cases of acc /ET an extra + 0.50 D could make some difference to the strabismus
  • 34. Undercorrection & overcorrection Undercorrect myopia in accommodative ET rarely tolerated Slight overcorrection of myopia in IXT Optical overcorrection or under correction in treatment of amblyopia(penalization)
  • 40. Ophthalmic Prism Ali Akbar Sabermoghaddam Associated professor of Ophthalmology Eye research center & Khatam eye hospital, MUMS
  • 44. Prisms bend rays toward the base. PRISMS P cm displacement 1 m = Prismatic Power (P ) apex base 100 cm X cm
  • 46. Ophthalmic Prism • Prisms function by bending rays of light towards the base of the prism. • The degree of bending of light depends upon the angle of incidence of light and the prismatic power.
  • 48. Ophthalmic prisms have been used in the treatment of binocular problems for more than 100 years.
  • 49. Ophthalmic Prism Corrective Prism: 1. Ground – In Prism. 2. Fresnel – On Prism (Press-on Prisms).
  • 50. Ophthalmic Prism PRESCRIBING INDUCED PRISM BY INTENTIONALLY DISPLACING THE OPTICAL CENTERS  Light traveling through the optical center of a lens encounters no prismatic power and passes through undeviated.  However, as the distance from the optical center increases, increasing prismatic power is encountered.  Prentice's rule : This is defined algebraically using the formula: Δ = hD where Δ = prism diopters , h = distance from the optical center in centimeters, and D= power of the lens in diopters.  Of note, the direction of displacement of light depends on whether the lens is of minus or plus power : - Minus lenses function as prisms held apex to apex; that is, as if the apex of the prism were at the optical center of the lens. - In other words, a ray of light traveling above the optical center encounters base-up prism power, and a ray traveling below the optical center encounters base-down prism.
  • 51.  In the mid 1960's, the 150-year-old Fresnel principle was applied to ophthalmic prisms for the first time. The first ophthalmic Fresnel prism, known as the "wafer" prism, was molded of an acrylic resin, making it much lighter and thinner than the corresponding powers of conventional prisms, thus extending the useful range of prism powers.  In 1970, the Press-OnTM prism, a Fresnel-principle prism molded in flexible plastic, was introduced to ophthalmologists. This thin, light membrane prism had the advantage of conforming and adhering to a smooth surface and thus could be affixed directly to a plano or basecurved correcting spectacle lens.
  • 56. Fresnel – On Prism • Fresnel prisms are constructed as a series of very narrow adjacent prisms on a thin sheet of plastic. • The prism is flexible, enabling it to conform to the base curve of the spectacle lens. • The commercially available powers of Fresnel prisms (in increments of 1 from 1 to 10, a power of 12, and in increments of 5 from 15 to 40).
  • 61. Ophthalmic Prism FRESNEL PRISMS  The prism is applied by pressing the smooth surface of the prism against the back surface of the spectacle lens while the lens is submerged in water.  Disadvantage of Fresnel prisms is that higher-power : - Introduce glare and chromatic aberration. - Significant decline in vision. - Minimal decline in visual acuity when using Fresnel prisms of 12 prism diopters or less
  • 62. Ophthalmic Prism Terminology a. Relieving Prism. • Action – Reduces the demand for controlling fusional vergence b. Inverse Prism. • Action – Increases the demand for controlling fusional vergence c. Yoked Prism • Action – Directs the eyes into a specific gaze direction d. Sector / Regional Prism • Action – Reduces the demand for controlling vergence in more than 1 gaze
  • 63. Ophthalmic Prism Indication : 1- Strabismus : - Comitant. - Non - Comitant (Diplopia) . 2 - Symptomatic heterophorias : Convergence training for exodeviation. 3 – presbyopia with symptomatic CI 4 - Nystagmus 5- Amblyopia 6- Cosmetic
  • 64. Ophthalmic Prism Prism For Deviations : 1. Exo: Base-In (BI) over either eye 2. Eso : Base-Out (BO) over either eye 3. RHT: - Base-Down (BD) over right eye - Base-Up (BU) over left eye 4. LHT : - BD over left eye - BU over right eye
  • 65. Ophthalmic Prism Prism For Head postures : 1. Left face turn Yoked prism base left 2. Right face turn Yoked prism base right 3. Chin elevation Yoked prism (BU) 4. Chin depression Yoked prism(BD)
  • 67. Ophthalmic Prism Adverse ( Reverse) Prism Indications : 1.To ignore the diplopic image 2.During convergence training for exodeviation: (BO Prism) 3.Cosmetics for patients who has very poor acuity in one eye or are poor surgical candidates (approximately 15 prescribed 4.Strengthening of the weak muscle
  • 68. 1- Strengthening of the weak muscle 2- Prevent Contractures of antagonist Adverse Prism
  • 70. Relieving Prism  In order to move the image to where the eye is looking, thus restoring fixation and binocular vision: For diplopia  Base of the prism is placed over the weak (or paralyzed muscles)
  • 71. Relieving Prism Surgical over and under-correction:
  • 75. DIPLOPIA Myasthenia Gravis, Multiple Sclerosis , Graves Disease OBLIQUE PRISMS :
  • 77. Symptomatic Heterophoria: Prismatic correction of exophoria Relieving Prism
  • 79. Prism for Symptomatic Heterophoria sheard’s criterion : Formula: prism needed=2/3 (phoria) – 1/3 (compensating fusional vergence) If a patient has 6 exophoria and base-out prism (BO) to blure is 6: 2/3 X6 -1/3X6=2  you would prescribe 2  base-in for this patient
  • 81. Prism for Other Medical - Bed-ridden patients. - Ankylosing spondylitis , - Other postural deformities.
  • 82. Ophthalmic Prism CLINICAL APPLICATIONS  In patients with tropias (small, comitant deviations) .  To ease asthenopia in patients with phorias.  Small-angle strabismus following intraocular surgery and  Residual deviations following strabismus surgery.  In most cases of superior oblique palsy, many patients will respond well to a small amount of vertical prism, with improvement in double vision and in head tilt as well.  Intermittent exotropia (to partially correct the angle of misalignment and decrease the fusional convergence requirement),  convergence insufficiency (best used with separate reading glasses to avoid introducing esotropia at distance),  divergence insufficiency (best used at distance only),  Anisometropia in the reading position (best treated with …
  • 83. Ophthalmic Prism OTHER CLINICAL USES OF PRISM  Prisms have been incorporated into contact lenses as a means of correcting vertical diplopia, but this method is only rarely used.  In some cases, prisms may be prescribed as a form of eye ‘exercise’, For example, in convergence insufficiency, the patient might be prescribed base out prism over both eyes to increase the exotropia at near.  This is typically provided as a removable Fresnel prism that is worn part of the day, with the goal of making the patient more comfortable the rest of the day when the prism is not worn.  Prisms may be used in the setting of nystagmus to improve head positions and to improve acuity.[To correct head positions, prisms are ‘yoked’ to shift the image into the null zone area. For example, a patient who has a right head turn and a null point in left gaze would be treated with base-out
  • 84. How to Prescribe a Prism for Combined Vertical and Horizontal Strabismus OBLIQUE PRISMS The Procedure  Estimating prism power. A good way to arrive at a starting prism power is to take the higher power prism measurement and add one-half of the lower power measurement.  For example, take a hypothetical patient with 20 prism diopters of esotropia and 10 PD of left hypertropia. The higher power measurement (20) is added to half the lower power measurement (10 ÷ 2 = 5). Therefore, a 25-PD handheld prism is selected.  Testing the prism. This prism is then placed before the nondominant eye. Assuming the left eye is nondominant, the 25-PD handheld prism would be placed with the base out and slightly down in front of the left eye to correct the combined esotropia and left hypertropia.  This prism is rotated slowly clockwise or counter-clockwise until the patient notes that the two images are fused.
  • 85. How to Prescribe a Prism for Combined Vertical and Horizontal Strabismus OBLIQUE PRISMS The Procedure  If the patient is unable to fuse, another prism is selected (start with a prism one increment higher or lower—in this case either a 30-PD or 20-PD and the process is repeated until fusion occurs.  Prescribing the prism. A wax pencil is then used to draw a line directly on the outside of the spectacles, using the base of the handheld prism as a guide. The clinician writes a prescription that includes the prism power and a statement regarding the orientation of the prism. For the above example, the prescription would read: ―25-PD Fresnel prism base out and down as marked.
  • 86. Ophthalmic Prism OBLIQUE PRISMS  Oblique prisms are required when trying to prescribe a single Fresnel prism for a combined vertical and horizontal deviation. Vector addition is used to combine horizontal and vertical prism. For example, combining 5 Δ base up with 5 Δ base out may be solved using the Pythagorean theorem (for a right triangle with sides a, b, andc, with c the hypotenuse, a2 + b2 = c2). In this case, 52 + 52 = c2 = 50; so, c = √50. Thus, 7.1 Δ of Fresnel prism may be prescribed base up and out in the 45° meridian. More complex combinations of vertical and horizontal prisms may be determined by applying basic trigonometric relationships of right triangles, or more practically by measuring the combination of vertical and horizontal prism in the lensmeter. When prescribing a combination of vertical and horizontal prism for ground-in prism, these calculations are not necessary, as most opticians prefer to be given the horizontal and vertical components separately.
  • 88. How to Prescribe a Prism for Combined Vertical and Horizontal Strabismus OBLIQUE PRISMS CASE ONE: A 75-year-old woman with Graves disease complained of diplopia.  Motility testing showed 25 PD of left hypertropia and 10 PD of esotropia.  A 30-PD handheld prism was chosen (25 + half of 10),  Held base down and out in front of the nondominant left eye.  The prism was rotated slightly clockwise and counter- clockwise until fusion occurred.  The outside of the glasses were marked with a wax pencil along the base of the prism.  An optician applied a 30-PD Fresnel prism with the base oriented as marked. The prism relieved the diplopia in primary gaze.
  • 89. How to Prescribe a Prism for Combined Vertical and Horizontal Strabismus (OBLIQUE PRISMS) CASE TWO: A 52-year-old woman developed incomitant strabismus with binocular oblique diplopia following an embolization procedure for a dural arteriovenous fistula.  Motility testing showed 10 PD of exotropia and 8 PD of left hypotropia in primary gaze.  A 15-PD handheld prism was chosen (10 + half of 8, rounded off to the closest available Fresnel prism power), held base in and up in front of the left eye,  Then rotated in a manner similar to that described above until fusion occurred.  The glasses were marked with a wax pencil.  The patient took the marked glasses to an optician for application of a 15-PD Fresnel prism, base in and up to the left spectacle lens.  The prism corrected the diplopia in primary gaze.
  • 91. Ophthalmic Prism SLAB-OFF PRISM  Patients who have anisometropia may suffer from diplopia or asthenopia when the line of sight does not pass through the optical centers of their spectacles.  This occurs because the displacement induces a net prismatic effect.  In general, most patients are able to use fusional abilities to adapt to the induced horizontal prism.  However, vertical gaze is often quite problematic. For example, a patient who has a refractive error of –3.00 OD and +1.00 OS will have induced prism when looking away from the optical center. If this patient looks 1 cm below the optical centers to read, the induced prismatic power will be 3Δ (1 cm ×3 D) of base-down prism on the right and 1Δ (1 cm ×1 D) of base-up prism on the left, giving a net prismatic effect of 4Δ base down on the right (base up on the left). Cover testing would reveal a 4Δ left hypertropia in the reading position.  There are several options for treating the vertical prismatic effects
  • 92. Ophthalmic Prism MEASURING PRISM IN SPECTACLES  The effective prism power in spectacle lenses is the combination of ground-in prism plus prism induced by displacement of the optical centers. To measure the amount of effective prism in spectacles, ask the patient to fixate on your own eye, then mark the point where line of sight intersects the lens using a felt tip marker. (The line of sight is the line connecting the object of regard with the center of the pupil.) The prism power at this location is the effective prism power. (This may or may not be the intended prism power depending on whether or not the optician correctly placed the optical center of the lens in front of the patient's pupil.) The glasses are then positioned on the lensmeter such that the mark on the lens is centered within the lensmeter port. If no prism is present, the mires representing the two cylindrical axes will intersect in the center of the lensmeter reticle. If prism is
  • 93. Ophthalmic Prism WRITING A PRISM PRESCRIPTION  When prescribing prisms, it is important to specify the amount and direction of the prism in addition to the lens or lenses into which the prism should be incorporated. Fresnel prisms are useful as a trial before grinding the prism into the spectacle lens. In our experience, it is best if Fresnel prisms are placed in the office or by a trusted optician; errors in positioning are frequent when the prisms are placed by inexperienced individuals.  Prescriptions requiring prism must be written with special care to avoid errors. It is advisable to communicate directly with the optician for particularly complex prescriptions. For combined vertical and horizontal deviations requiring oblique Fresnel prisms, the axis of the base must be specified using degrees as for astigmatic lenses. However, the astigmatic axis allows for two positions of the base; that is, ‘10Δ base 30°’ could be interpreted as ‘10Δ base up-and-out in the 30° meridian’, oras ‘10Δ base down-and-in
  • 95.  Indication - Comitant Strabismus - Non - Comitant Strabismus (Diplopia) : - Eliminate abnormal head position - Provide single binocular vision - Symptomatic heterophorias . - Abnormal head postures. - Nystagmus. • In a patient with a long-standing paresis, what are the considerations when prescribing prism? • In a patient with a recent onset paresis, what are the considerations when prescribing prism? • How do you prescribe prism using Sheard’s criterion? • How do you prescribe prism using Caloroso’s Residual Vergence Demand Criterion?
  • 96. Terminology a. Corrective or Neutralizing Prism: • Goal – To stabilize normal sensory fusion • Prism Action – Neutralizes the demand for controlling fusional vergence b. Relieving Prism: • Goal – To stabilize sensorimotor fusion • Action – Reduces the demand for controlling fusional vergence c. Overcorrective Prism: • Goal – To disrupt anomalous correspondence • Action – Reverses the demand for controlling fusional vergence
  • 97. Terminology d. Inverse Prism for Training or Disruptive Prism Therapy: • Goal – To increase fusional vergence ability • Action – Increases the demand for controlling fusional vergence e. Inverse Prism for Cosmesis: • Goal – To enhance cosmesis of a strabismus when a patient has poor treatment prognosis • Action – Optically displaces the image of the eyes in a direction opposite the strabismus when an observer views the patient. f. Yoked Prism: • Goal – To stabilize bv in non-concomitancy or dampen nystagmus • Action – Directs the eyes into a specific gaze direction g. Sector / Regional Prism: • Goal – To stabilize binocular vision in one or more gaze positions • Action – Reduces the demand for controlling vergence in more than 1 gaze
  • 100. 4. Constant Strabismus  a. Corrective Prisms for Resolvable Strabismus  • Avoid using prism when patient has Anomalous Correspondence, peripheral suppression, amblyopia.  • Must have normal correspondence and normal peripheral sensory fusion  • Monitor for prism adaptation. Can use temporary Fresnel prisms.  • Once normal sensory fusion achieved for 3-6 months (can be less for infants)  - Titrate prism 2-4Δ at a time
  • 101.  3M Press-On™ Optics  AVAILABLE PRISMS and ASPHERIC LENSES PRISMS ASPERIC - PLUS ASPERIC - MINUS ASPERIC - D-SEGS  Diopter Power Power Power  1.0 􀁕 + .5 -1.0 1.0  2.0 􀁕 +1.0 -2.0 1.5  3.0 􀁕 +1.5 -3.0 2.0  4.0 􀁕 +2.0 -4.0 2.5  5.0 􀁕 +2.5 -5.0 3.0  6.0 􀁕 +3.0 -6.0 4.0  7.0 􀁕 +3.5 -7.0 5.0  8.0 􀁕 +4.0 -8.0 6.0  9.0 􀁕 +5.0 -9.0  10.0 􀁕 +6.0 -10.0  12.0 􀁕 +7.0 -11.0  15.0 􀁕 +8.0 -12.0  20.0 􀁕 +10.0 -13.0  25.0 􀁕 +12.0 -14.0  30.0 􀁕 +14.0  35.0 􀁕 +16.0  40.0 􀁕
  • 104. Conditio n Relevant Issues Function of 3M Press- On prism Suggested use of 3M Press-on Prisms STRABISMUS Early onset strabism s Surgical over and under- correction is a common problem Preoperative prism adaptation enhances surgical outcome or establishes fusion nonsurgically. To obtain presurgical fusion without weight, thickness, and incoveniene of conventional prisms To provide a fusion lock and stability for post-surgical residual deviations.
  • 105. Condition Relevant Issues Function of 3M Press- On prism Suggested use of 3M Press-on Prisms STRABISMUS Mild Amblyopia Requires early intervention to avoid progression Applied over the preferred eye as a weak patch Small image degradation of prism serves as weak occluder Prisms blurs visual acuity in dominant eye
  • 106. Condition Relevant Issues Function of 3M Press- On prism Suggested use of 3M Press-on Prisms STRABISMUS Nystagmus Can allow patient to assume a more normal head position to find the null point of the nystagmus Prisms with the base away from the direction gaze preference can allow the eyes to rotate into position without a large head turn Redirects the visual gaze toward the fireld of minimal tremor Requires placement of prisms over both lenses. In absence of strabismus ,the power needs to be matched.
  • 107. Condition Relevant Issues Function of 3M Press- On prism Suggested use of 3M Press-on Prisms STRABISMUS Inoperable strabismus Fragile health or patient concerns may delay or preclude surgery Provides cosmetic improvement by shifting the apparent position of the eye in a desirable direction For cosmetic improvement of certain tropias with an inverse prism applied before the deviating eye (e.g.,base-in prism for esotropia). For constant tropias where surgery is not contemplated and binocualr fusion is not possilbe Cosmesis
  • 108. Condition Relevant Issues Function of 3M Press- On prism Suggested use of 3M Press-on Prisms DIPLOPIA Associated with several health issues, I.e. including mechanical restrictions, neurologic disorders (nerve palsies), poststroke skew deviation, postretinal detachment,scleral buckles, thyroid ophthamology , injuries such as blowout fractures and brain injuries 3th, 4th , and 6th nerve palsies May recover with time Allows binocularity during recovery period. May be changed as muscle function returnes. To eliminate diplopia resulting from recent- onnset strabismus (e.g.stroke, ocualr muscles paresis systemic disease)
  • 109. Condition Relevant Issues Function of 3M Press- On prism Suggested use of 3M Press-on Prisms DIPLOPIA Associated with several health issues, I.e. including mechanical restrictions, neurologic disorders (nerve palsies), poststroke skew deviation, postretinal detachment,scleral buckles, thyroid ophthamology , injuries such as blowout fractures and brain injuries Incomitant strabismus Deviation varies with gaze direction0 Applied over part of a lens at allow correction in specific gaze positions. For incomitant strabismus, which demands different prism power in certain fields of gaze Prisms can be easily cut and placed on spectacles for correction where needed
  • 110. Condition Relevant Issues Function of 3M Press- On prism Suggested use of 3M Press-on Prisms PHORIAS Symptomatic or Decompensate d phorias Fusion disruption causes eyes to deviate Promotes, fusion reduces deviation For symptomatic phorias with different distance and near angles, apply prism to upper and/or lower portions of spectacle lenses
  • 111. Condition Relevant Issues Function of 3M Press-On prism Suggested use of 3M Press-on Prisms Other Medical Indications for Press-On prisms Bed-ridden patients Cannot elevate head to read or watch television Based-down prisms on both lenses change image’s angle Apply 30* prism base down to each spectacle lenses Ankylosing spondylitis other postural deformities Limited head movement Prisms change image’s angle Apply prism base up to spectacle lens
  • 113. case1  A 45 years- old man who had car accident two week ago came with intractable diplopia .  Vision: 20/20(o.u)  Motility: 40 prism diopter ET with limitation of abduction(-4) in right eye.  Fundus: normal. What is your management
  • 114. case2  15 years old boy referred to strabismus clinic for deviation. He had occasional deviation especially after illness and complain of asthenopia.  BCVA:OU:20/20  Refraction:-0.5sph(OU)  EOM:10 prism diopterX(far),2o prism diopterX (near)  Fundus: normal What is your plan?What is your plan?
  • 119. Other indication  Fourth Nerve Paresis  Accommodative Esotropia  Acquired Esotropia  Intermittent Exotropia  Multiply Operated Strabismus  Thyroid Ophthalmopathy  Nystagmus
  • 120. Sixth Nerve Paralysis  Acute cases of any age or origin are followed without treatment for 3 to 4 weeks  If healing begins within a month it typically will be progressive and complete  After 1 month, if disabling diplopia persists and recovery is not progressing, or if a child remains esotropic in all gaze positions so that binocularity is threatened, then injecting the medial rectus (MR) on the affected side(s) is appropriate
  • 121.  for diabetic patients who have a generally good prognosis, the value of botulinum toxin treatment lies in earlier rehabilitation.  botulinum toxin to release MR contracture makes it appropriate to wait a full 6 months after the onset before transposition surgery  Injection several months after surgery has corrected several undercorrected transposition cases and may need to be repeated.
  • 123. Infantile Esotropia  Simultaneous bimedial toxin injection is quite successful  All reports include 2 years or more of follow-up and show high correction rates of 60% to 80% with multiple injections  Perform simultaneous bimedial injection  Inject as early as age 3 months.  Repeats simultaneous bimedial injection with recurrence of esotropia exceeding 15 PD
  • 126. Side effect  Ptosis  Induced vertical deviation  Hemorrhage  Pupillary dilation  Globe perforation
  • 128. orthoptics  Goal is give comfortable binocular vision  used to combat suppression,amblyopia,ARC,enhance fusional amplitude and improve stereopsis  In successful case transform tropia to phoria but not eliminate it  Supervision and direction of treatment responsibility of ophthalmologist
  • 129. Application  Convergence insufficiency  Fusion training  Antisuppression training  ARC
  • 130. Convergence insufficiency  Most effective treatment  Converge on an approaching object such as pencil or a light while red filter is placed over one eye  Aware of physiologic diplopia of a distant object while fixing on a target at near  Training fusional convergence with base out prism or major amblyoscope  Base out prism used during reading and continue on home with increasing power
  • 131. Fusion training  Training of fusion amplitude enable symptomatic heterophoria patient more comfortable  Done by major amblyoscope or prism exercise
  • 132. Antisuppression Training  Orthoptic is aimed to awareness of physiologic diplopia in heterophoria and diplopia in heterotropia  Once diplopia elicited vergence control activated  Forcing suppressed area concurrently with corresponding area of dominant eye  Stimulation of retina of deviated eye by moving visual target on major amblyoscope back and forth across suppression scotoma  Suppression cannot be effectively eliminated by orthoptic
  • 133. ARC  Treatment is no longer practiced  The methods that were used are historical and theoretic  Based on principle that if the image of the fixation point is moved with the amblyoscope over the retina of the deviated eye anomalous localization of the double image may suddenly be replaced by normal localization  ARC had benefit in preserving advantage of normal binocular vision so do not treat it