Cataract (Classification-Etiology)

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Cataract (Classification-Etiology)

Shadi Awwad, MD

I. Classification
A. Morphologic
B. With respect to maturity
C. Age of onset A. Morphologic:
1. Capsular Cataract
a. Anterior Capsular
-Congenital: from persistent pupillary membrane
-Acquired: Pseudoexfoliation syndromes, chlorpromazine, in association with posterior
synechiae
b. Posterior capsular:
-Congenital: in association with persistent hyaloid remnants (Mittendorf's dot)
2. Subcapsular Cataract
a. Posterior Subcapsular
-Complicated (e.g. in Diabetes Mellitis, Myotonic Dystrophy, steroids, irradiation)
-Age -related
Fig.1: Posterior Subcapsular Cataract ( click to enlarge)
Fig. 1: Annotated (click to enlarge)
Fig. 2: Posterior Subcapsular Cataract (by retro illumination)
b. Anterior Subcapsular
-Acute angle closure glaucoma(Glaukomfleckens), amiodarone toxicity, miotics,
Wilson's disease
Fig. 3: Anterior Subcapsular Cataract (click to enlarge)
Fig. 3 Annotated
3. Nuclear Cataract
-Age-related
-Congenital: Rubella, Galactosemia
4. Cortical Cataract
-Usually spoke-like, can be anterior or posterior
-Can be congenital (very common)
-Usually doesn't interfere with vision
5. Lamellar Cataract
-Congenital. Involves one lamella of the fetal or nuclear zone
6. Sutural Cataract
-Congenital
-Very common
-Y-shaped opacity in the lens nucleus
-No clinical significance

B. Maturity
1. Immature Cataract
-scattered opacities are separated by clear areas
2. Mature
-Cortex is totally opaque
Fig. 4: Mature Cataract (click to enlarge)
Fig. 5: Cataracta Rubra (click to enlarge)
3. Intumescent
-The lens has become swollen by imbibed water
-Can be mature or immature
4. Hypermature Cataract
-Mature cataract that has become swollen and has a wrinkled capsule as a result of
leakage of water out of the lens.
5. Morgagnian Cataract:
-Hypermature cataract leading to total liquefaction of the cortex making the nucleus sink
inferiorly

C. Age of onset
1. Congenital
2. Infantile
3. Juvenile
4. Pre-senile
5. Senile
II. Etiology
A. Age-related
1. Sub-capsular
a. Anterior: due to fibrous metaplasia of the anterior lens epithelium
b. Posterior: just in front of the posterior capsule. It is associated with the posterior
migration of the anterior epithelium of the lens
-Patients with posterior sub-capsular cataract are more troubled than those with the
anterior ones, particularly from headlights of oncoming cars and bright sunlight.
-Near vision in these patients is also poorer than distance vision
2. Nuclear Cataract
-Exaggeration of the normal aging involving the lens nucleus (frequently preceded by
radial water clefts in the cortex.
-Often associated with myopia from the increase in the refractive index and increase
in the bi-convexity of lens. Some elderly patients with Nuclear Sclerosis may be able
to read again without their spectacles, due to the induced myopia: this explains the "second
sight of the aged".
B. Trauma can cause cataract: concussion, penetrating, electric shock or lightening.
C.. Metabolic
1. DM
-Senile cataract is accelerated
-True diabetic cataract: associated with over-hydration. Results in bilateral white punctate
or snowflake posterior or anterior sub-capsular opacities
2. Galactosemia, Glalactokinas deficiency, mannosidosis, hypocalcemic syndromes
(multifocal white flakes)
3. Toxic
-Steroids: systemic cause more cataract than topical. A dose <10mg/d or given for less than
one year is generally safe. Individual variability as well as dose and duration are all important.
Cause anterior and posterior sub-capsular lens opacities.
-Chlorpromazine: causes anterior lens capsule opacities
-Amiodarone: causes anterior sub-capsular opacities.
-Gold (used in Rheumatoid Arthritis): 50% have posterior lens opacities
-Miotics: cause anterior sub-capsular opacities
4. Secondary Cataract
-Chronic anterior uveitis
5. Miscellaneous
-Hereditary fundus dystrophy: Retinitis Pigmentosa, Leber's,..
-High Myopia
-Acute angle closure glaucoma (Glaukomfleckens): anterior capsular or sub-capsular
opacitiesin the pupillary zone
-Myotonic Dystrophy: Fine polychromatic granules in the cortex( "Blue-dot cataract"),
followed later by sub-capsular stellate opacities ("Christmas tree")
Fig. 6: Blue dot cataract (click to enlarge)
-Atopic Dermatitis: bilateral anterior or posterior stellate opacities
-Down's syndrome
6. Intra-uterine
-Congenital Rubella: 15% of cases. After the 6th week, the virus is no more capable of crossing
the lens capsule.
-Toxoplasmosis
-CMV
-Maternal ingestion of Thalidomide, steroids,...


7. Hereditary
-Usually dominant
-Congenital to pre-senile