This is a seminar presentation conducted by 4th year medical student under supervision of a lecturer. This is for ophthalmology posting seminar. Source of information are from google, few textbooks and also based on previous ophthalmology posting group's seminar.
2. ANATOMY OF THE LENS
A biconvex structure attached to
the ciliary process by the zonular
fibre, between iris & vitreous
humour
Non-vascular, colourless and
transparent
Index of refraction 1.336
Consists of stiff elongated,
prismatic cells known as lens fibre,
very tightly packed together
Divided into nucleus, cortex and
capsule
The whole lens enclosed within an
elastic capsule
Helps to refract incoming light
and focus it onto the retina
3. ANATOMY OF THE LENS
STRUCTURE OF THE
LENS:
LENS CAPSULE
ANTERIOR LENS
EPITHELIUM
LENS FIBER
4. ANATOMY OF THE LENS
LENS CAPSULE
Thin transparent, collagen
membrane
Surrounds lens
completely
Elastic in nature but
contain no any elastic
tissue
Anteriorly secreted by
lens epithelium and
posteriorly by basal cells
of elongating fibers
5. ANATOMY OF THE LENS
ANTERIOR LENS EPITHELIUM
Single layer below the lens
capsule
Formed of cuboidal cells
Become columnar at equatorial
region
LENS FIBER
The epithelial cells elongated to
form lens fibers which have a
complicated structural forms.
Mature lens fibers are cells
which have lost their nuclei.
As the lens fibers are formed
throughout the life, these are
arranged compactly as nucleus
& cortex of the lens.
6. ANATOMY OF THE LENS
NUCLEUS
Its is the central part containing
the oldest fibres. It consists of
different zones, which are laid
down successively as the
development proceeds.
Different zones:
I. Embryonic nucleus
II. Fetal nucleus
III. Infantile nucleus
IV. Adult nucleus
CORTEX
Its is the peripheral part which
compromises the youngest
lens fibres.
7. LENS TRASPARENCY
Its transparency is due to the arrangement of its
fibres, internal structure and the biochemistry of
the lens cells and fibres.
A cataractous lens is when the lens become
opaque.
8. CATARACT
Cataract is a clouding of the lens or any opacity within the lens
which leads to a decrease in vision
WHAT IS CATARACT?
17. CLASSIFICATION
BASED ON DEGREE OF MATURITY
HYPERMATURE MORGAGNIAN
Cataract is shrunken
and wrinkled anterior
capsule due to leakage
of water out of the lens
Cataract is a
hypermature cataract in
which liquefaction of
the cortex has allowed
the nucleus to sink
inferiorly
MATURE IMMATURE
Cataract is one in which
the lens is completely
opaque.
Cataract is one in which
the lens is partially
opaque.
18. IMMATURE CATARACT
Features:
Opacification becomes more diffuse and irregular.
Iris shadow still visible.
Lens is not completely opaque
Wedge shaped opacities at periphery of the lens
Progress gradually
19. IMMATURE CATARACT
When there is any clear cortex between the iris and
the opacity (greyish white in immature senile
cataract), the shadow of the iris which falls upon
the opacity, as light is cast upon the eye is visible
through the clear cortex. This is called the ‘iris
shadow’ and is a common sign in immature senile
catarct.
IRIS SHADOW IN IMMATURE CATARACT
20. IMMATURE CATARACT
WHAT IS THE IRIS SHADOW?
Black crescent
Due to the presence of clear interval between
iris and lens opacity
21. MATURE CATARACT
Symptoms
- Usually severe decrease in vision.
Features
- Complete opacification of the lens capsule, cortex and the
nucleus
- Lens appears pearly white in colour.
Also known as ripe cataract.
May progress to hypermature cataract
May be complicated with phacolytic glaucoma.
23. MATURE VS IMMATURE
HOW TO DIFFERENTIATE MATURE AND IMMATURE CATARACT?
IMMATURE CATARACT MATURE CATARACT
Visual acuity is reduced to
counting fingers
Visual acuity is reduced to hand
movement or perception of light
Lens is partially opaque Lens in totally opaque
Iris shadow is present No iris shadow is present
Fundus may be visible No fundus details
24. HYPERMATURE CATARACT
Which is characterized by wrinkling of the capsule due
to liquefied lens cortex and morgagnian
cataract (sinking of lens nucleus inferiorly within the
capsule)
This can cause inflammation, eye pain and headache
(if complicated by glaucoma)
A hypermature cataract is rare and needs removal
26. MORGAGNIAN CATARACT
Complete cortex is liquefied and appears milky white in
colour.
Nucleus settles at the bottom
Calcium deposits may also be seen on the lens capsule.
28. PATHOPHYSIOLOGY
The lens is made mostly of water and
protein fibers.
Opacity occur when the lens protein
(crystallins) clump together
Ability for lens to refract lights reduce
which cause reduce visual acuity.
Chemical modification of the lens
cause it to be thicken and harden
29. PATHOPHYSIOLOGY
It is not fully understood.
There are three metabolic pathways which convert
glucose in energy (ATP) and other relevant metabolic
molecules. These are:
1. Glycolysis
2. The Pentose Phosphate Shunt
3. The Polyol Route
30. 1. GLYCOLYSIS
Aging
Decrease in Hexokinase
concentration
Drop in ATP level
Poor control of
electrolyte balance
Massive influx of water
into the lens
Disorganization of structured
proteins in the lens
Aggregation and precipitation of
protein
CATARACT
32. 3. POLYOL PATHWAY
High glucose level in blood Polyol Pathway
GlucoseSorbitol
Accumulation of sorbitol in lens Hyper osmotic effect - Influx of excess
water through aquaporin channels
CATARACT
Aldose Reductase
Polyol dehydrogenase has low Km for sorbitol
34. DIABETES & CATARACT
Cells use glucose for energy. This normally occurs by
phosphorylation via the enzyme hexokinase.
However, if large amounts of glucose are present (as in
diabetes mellitus), hexokinase becomes saturated and the
excess glucose enters the polyol pathway when aldose
reductase reduces it to sorbitol.
35. DIABETES & CATARACT
Hexokinase can return the molecule to the glycolysis
pathway by phosphorylating fructose to form fructose-6-
phosphate. However, in uncontrolled diabetics that have
high blood glucose - more than the glycolysis pathway can
handle - the reaction's mass balance ultimately favors the
production of sorbitol.
36. POLYOL PATHWAY
The retina cells use glucose for energy as normal, and
any glucose not used for energy will enter the polyol
pathway. When blood glucose is normal, this
interchange causes no problems, as aldose reductase
has a low affinity for glucose at normal concentrations.
In a hyperglycemic state, the affinity of aldose
reductase for glucose rises, causing much sorbitol to
accumulate. This change of affinity is what is meant by
activation of the polyol pathway.
37. POLYOL PATHWAY
When sorbitol collects in the lens, it can affect cells and
naturally-occurring proteins, causing the lens to become less
clear and more opaque. This condition eventually leads to
cataract formation.
38. CLINICAL PRESENTATION
Decreased visual acuity is the commonest complaint.
- Progressive and painless
- Worse in bright light
There may be complaint of glare and monocular diplopia if the
cataract splits the visual axis
A myopic shift in the refraction with progression of cataract may
also be noted
Some complain of a white reflex in the pupil
PRESENTING COMPLAINTS AND HISTORY
39. CLINICAL PRESENTATION
PAST MEDICAL HISTORY
May reveal risk factors such as
- Trauma
- Intrauterine infections
- Diabetes or other metabolic disorders
Cataract may have occurred in other members of the
family in the hereditary variants.
FAMILY HISTORY
40. PE FINDINGS
Visual acuity is impaired for both distance and near and
patient may even be blind.
Opacity in the lens
Ocular adnexia and intraocular structures when examined
may reveal lesions that may point at
- The cause, type and eventual visual prognosis
If RAPD positive, this indicates an optic nerve disease or
extensive macular lesions
- Visual prognosis guarded in such cases
46. TREATMENT
The treatment of cataracts is :
1. Glasses
2. Better lighting
3. Surgery
a. Phacoemulsification
b. ECCE
c. ICCE (not performed now)
Sometimes a cataract should be removed even if it doesn't
cause major problems with vision, if it is preventing the
treatment of another eye problem, such as age-related
macular degeneration, diabetic retinopathy or retinal
detachment
47. TREATMENT
The aim of treatment is:
1. Improve vision
2. Increase mobility and independence
3. Relief from the fear of going blind
48. INDICATIONS
1. Work or lifestyle is affected by vision problems caused by the cataract.
2. Glare caused by bright lights is a problem.
3. Cannot pass a vision test
4. Have double vision.
5. Notice a big difference in vision when you compare one eye to the
other.
6. Have another vision-threatening eye disease, such as diabetic
retinopathy or macular degeneration.
49. SURGERY: ICCE
Intracapsular cataract extraction
Involves extraction of the entire lens, including the
posterior capsule and zonules
Weak and degenerated zonules are a pre-requisite for this
method
This is the surgery of choice if there is markedly
subluxated or dislocated lens
This technique of surgery has largely been replaced by
ECCE
50. SURGERY: ECCE
Extracapsular cataract extraction
An 5 mm to 6 mm incision is made in the eye where the
clear front covering of the eye (cornea) meets the white
of the eye (sclera).
Another small incision is made into the front portion of
the lens capsule. The lens is removed, along with any
remaining lens material.
An IOL may then be placed inside the lens capsule. And
the incision is closed.
*it is usually done if the cataract is too large to be destroyed
by ultrasound
52. COMPLICATIONS
1. Infection in the eye (endophthalmitis).
1. Swelling and fluid in the center of the nerve layer (cystoid
macular edema).
1. Swelling of the clear covering of the eye (corneal edema).
1. Bleeding in the front of the eye (hyphema).
1. Detachment of the nerve layer at the back of the eye (retinal
detachment).
53. ICCE VS ECCE
ECCE ICCE
Small incision 5-6mm Large incision 10-12mm
Posterior lens conserved Removal entire lens
No stiches required, self healing Required stiches, long rehabilitation
time
IOL implant Aphakic eye
Post operative complication minimal Added risk for retinal detachment,
corneal edema and vitreous loss
54. PHARMACOEMULSIFICATION
Two small incisions are made in the eye where the clear front covering
(cornea) meets the white of the eye (sclera).
A circular opening is created on the lens surface (capsule)
A small surgical instrument (phaco probe) is inserted into the eye.
Sound waves (ultrasound) are used to break the cataract into small pieces.
Sometimes a laser is used too. The cataract and lens pieces are removed
from the eye using suction.
An intraocular lens implant (IOL) may then be placed inside the lens
capsule.
Usually, the incisions seal themselves without stitches.