Refraction and Retinoscopy

Dr. Dimple Prakash
Head Post Graduate Training Programme

Plane Mirror Retinoscopy
in case of Welsch Allen retinoscope
when the lens is pushed down the
mirror acts like a plane mirror and the
rays are divergent.

Concave Mirror Retinoscopy
When the lens is pushed up the mirror
acts like a concave mirror so the rays are
convergent.
Practical importance : in plane mirror
retinoscopy a with movement will need +
lenses but in concave mirror retinoscopy
a with movement will need – lenses.

Illumination Stage Reflex Stage

Projection Stage

• Rays are from S1
• Image is at far point of subject
• Shadow at pupil of subject
• Projected to the examiner

Normal Eye

+1.50

66 cm

Hyperopia (Small Eyes)

+58 D

Myopia (Large Eyes)

+62 D

Break :
Width : Narrowest when
allingned with true axis
Intensity : Brightest when
along with true axis
Skew : When axis is not
assigned reflex breaking
into two

Low Errors High Errors
Speed High Low

Brilliance Bright Dull

Width Wide Narrow

Neutralization point : complete illumination of entire
pupillary area.

Swirl

Checking axis : Swirl WAKE UP

 2.00DC @ 80

 Add 45 degrees = 125

 Minus 45 degrees = 35

 Keep the streak at 125 and 35

 Note the width : should be equal

 Side that is less : change axis
slowly towards wider side.

GROSS NET

Power of lens Following
that is held in subtraction of
front of the distance and
examined eye cycloplegic
at which drops
neutralization
occurs

Distance Subtraction Cycloplegic
1 mt = 1 D Atropine = -1.00 D
2/3 mt = 1.50 D Homatropine = -0.50 D
Cyclopentolate = -0.75 D

Example Distance (lm) Atropine
+6.00 DS  +5.00 DS  +4.00 DS

Few Algebraic rules for signs of Cylinders

- - = + - 6.00 - 4.00 = - 2.00

- + = + - 6.00 + 4.00 = - 10.00

Practice Situations

Net + 6.00

+ 4.00

Lower Value = Sphere = +4.00
Difference = Cylinder = +2.00
+ 4.00 - +6.00 = - Sign of cylinder
Axis at lower value = 180
+ 4.00 DS / -2.00 DC @ 180 Axis

90 Axis
Net - 6.00 DS
- 4.00 DS
180 Axis

* Lower value here is – 6.00 DS
The rest is the same
- - = +
- 6.00 DS / +2.00 DC x 90 Axis

- 8.00 DS
WAKE UP
- 10.00 DS

- 10.00 / +2.00 DC x 180 Axis

Sample Transpositions
- 2.00 DS / -4.00 DC x 180 Axis

1. Allegebric sum of the sphere and cylinder
- 6.00 DS

2. Change the sign of the cylinder
- 6.00 DS / +4.00 DC

3. Change the axis if above 90 = minus 90
if below 90 = add 90
- 6.00 DS / +4.00 DC @ 90 Axis

Methods
 Easiest : fogging. Over refraction,
over retinoscopy

 Duchrome testing

 Jackson cross cylinder

 Astigmatic dial

 Astigmatic fan and block

Jackson Cross Cylinder
 Components: sphere

 Cylinder

 Power: ½ that of cylinder

 Axis of Cylinder : 2 are
perpendicular to each other

 Handle: 45 degrees always.

How it works?
 Axis first: handle in direction of
the cylinder in the frame already.
Eg) 2.00DC at 180 then keep
handle at 180

 Va chart 2 lines above least visible.
eg)6/12 if BCVA is 6/6.

 Flip + 0.50 or – in front of patient.

 At best vision point, rotate the DC
by 10 degrees towards the red
mark in case of – and towards
white mark in +.

 E.g.) DC in trial frame= +2.00DC @
180

 BCVA CLEAR when +0.50 DC is in
front

 Rotate 10 degrees towards white
mark

 +2.00 DC@ 170.

How it works?
WAKE UP
 Power of DC. This is easy.

 Keeping the correct axis. Flip the
JC by + or – and then add or
subtract the correct power.

 E.g.) DC in trial frame = +2.00,Va
better at +0.50 DC then final
value= +2.50 DC.

 If equal Va at 2 flips: correct
power.

Summary
 Most plus or least minus sphere:
BCVA

 Va chart 2 lines above least visible.
eg)6/12 if BCVA is 6/6.

 No cylinder, still flip at
90,180,45,135.

 Axis first : Why?

 Lower powers 0.25 for 20/30 Va
.Flip + 0.50 or 1.00 for lower

Duchrome

 Chromatic aberration

Duchrome
 Normal : both equal
 Start with Red slightly better
 Focus on the letters

 Hyperope of +5.00 sees green
better, increase to +5.25 D so sees
red better.

TE
A K
• Increasing the converging power so that
“STRONGEST + LENSES “ are given.
(asthenopia)

 Myope: - 5.00D sees red better leave
him alone
 -5.00 D sees green then – 4.75 D get
the rays in front.

PO
N F
• “WEAKEST (– )LENSES”

Fogging
Indications : Young
: Recurrent Asthenopia
: H/O Squeezing / frowning
: Difficulty in near work
(E.g.) Needle work, Microscope
Reference Chart :
If we start pt +20.00 DS upto +16 D: Decrease in lens in strengths of +2.00 DS

(E.g.) +20.00 D = Next lens + 18.00 DS

+16 D TO +12/10 D: Decrease in strengths of 1.00 DS
(E.g.) +10.00  +9.00 DS, +8.00 etc

Upto (+6.00 DS. From then upto +4.00 DS : +0.50 DS decrease
+5.50, +5.00, +4.50 etc

Giving Glasses
Age
Hyperopia Fogging
Refinement methods
1) Less than 3 years = Full retinoscopic correction
Eg; +4.00 DS = Give + 4.00 DS
Presence of tropia
2) 3 to 8 years
Presence of phoria
Esotropia = Full gross value subjective to AC/A ratio
Phoria = Full net  optimal, under correction
Eg. Net Value
+4.00 D in phoria = +3.50 / +3.75 which is accepted

3) Adults follow : rule of strongest +

Hyperopia
with Age
Correction
HM 6.50
6.00
5.50
5.00
4.50
4.00
3.50
3.00
2.50
2.00
1.50
1.00
0 1 2 3 4 5 6 7 8 9 10 11 12 YRS

Giving Glasses : MYOPIA
Thumb rules
 Normal patients

1) From -1.00 to -6.00 DS : Full correction

2) Above -6.00 DS : Under correct to meet subjectiveness

 Esotropia

High presence of -6.00 DS and above are under corrected
meet acceptance followed by optimal to full correction

 Exotropia
Over correct in intermittent EXOTROPIAS

Giving Glasses : Astigmatism

 Normal patients WAKE UP

: In a child less than 3 years = 1.25 DC,
Regular

: Older than 3 years = all astigmatism to
be corrected

• Child : follow-up 6 months
• Adult yearly
• Frequent change : over correct (0.25 D)

Giving glasses: child
 Ideal frame: large, sturdy, well
balanced
 Ideal lenses: plastic,
polycarbonates
 Ideal refraction:
 Less than 3 years: solely on
retinoscopy
 All strabismus : retinoscopy
 Beyond 3 years: myopes do not
need

Cycloplegic studies
 Rosenbaum and associates: atropine
estimation of hyperopia 0.34 D more
as compared to homatropine
 Hurol et al: no difference between 2
and 3 days of cycloplegia
 Stolovich: 8 instillations vs 4
instillations.

Bifocals
 Working distance

 0.2 m wide or smallest test
type

 Blurred/ not readable = near
point

 No doubling

 Keep 1/3rd reserve

Tips on bifocals

 Keep 1/3rd reserve

 Undercorrect

 Full correction 23 mm of near
point max (3.5D)

 Prisms for convergence thereafter

Practical Tips
Do Don't
Read Previous prescription Don’t make drastic glass
changes from past
“Suspicion”
Bifocal to progressive
progressive to Bifocals

Adjust sphere first
Do not try to change to
E.g.) +1.25 DS / -0.75 DC
higher astigmatism
Change to +1.75 to +1.50 +1.25 DS / -1.25 DC

Practical Tips
Do Don't
4. Try to correct the axis
rather than the number
Eg) -0.75 DC @ 90 Ax
change to -0.75 DC @ 100
Ax rather than -1.00 DC @
90 Ax

Final Example
-1.25 DS / -0.75 @ 80 Ax

(a) -1.50 DS / -1.75 DS with -0.75 DC @ 80 Ax J
(b) -1.25 DS / -0.75 DC @ 90 Ax J
(c) -1.25 DS / -1.00 DC @ 80 Ax J

L -1.50 DS / -1.50 DC @ 80 Ax

Make the right choice

 Low powers : smile and
bye bye
 High plus: think!
Chromatic aberrations
prismatic aberrations
 High index lenses:
1.6 and 1.74
 Thinner, flatter, lighter
 +4.00 D = high index

 Gets higher : plastic lenticular
lenses
 Aspheric lenses : curves that
flatten away from the center.
Prismatic effects
 Myopes: higher powers -4.00
above 1.6 high index

Power refraction you are now armed

 Retinoscopy
 Interpretation of numbers
 Giving glasses
 Refinement of numbers
 What not to do

Dr. DIMPLE PRAKASH
Senior Consultant
Pediatric and Squint
Head Post Graduate Training Programme

Refraction and Retinoscopy

Recomendados

Recomendados

Mais conteúdo relacionado

Mais procurados

Mais procurados (20)

Semelhante a Refraction and Retinoscopy

Semelhante a Refraction and Retinoscopy (20)

Mais de Dr. Agarwal's Group of Eye Hospital

Mais de Dr. Agarwal's Group of Eye Hospital (19)

Último

Último (20)

Refraction and Retinoscopy