CONGENITAL CATARACT

Developmental cataract may be present at birth (congenital) or it may develop later 

The critical period for developing the fixation reflex in both unilateral and bilateral visual deprivation disorders is between 2 and 4 months of age. 

Causes

1. hereditary (25%) usually Autosomal dominant

2.  maternal infections like rubella

3.  chromosomal disorders like down syndrome

4.  metabolic disorders like galactosemia 

5. ideopathic: unilateral cataracts are usually sporadic

clinical Types

1. blue dot cataract

2. anterior capsular cataract

3. posterior capsular cataract

4. coronary cataract

5. zonular cataract: This accounts for approximately 50% of all visually significant congenital cataracts

investigations 

1. ocular examination

   1. morphology and density of cataract based on vision and visiblity of fundus as seen by direct and indirect ophthalmoscope

   2. cycloplegic refraction in partial cataract

   3. associated pathology including microphthalmos , increased intraocular pressure is noted

   4. B-scan in compete cataract to see retinal pathology like retinal detachment and retinoblastoma

   5. A-scan is done to record axial length and compare the two eyes

2. systemic examination

   1. Serum biochemistry is done to find out levels of fasting blood glucose, calcium and phosphorus,

   2. galactokinase level.

   3. Urine analysis for the presence of reducing substances after milk feeding (galactosemia),

   4. screening for amino acids in urine (Lowe’s syndrome)

   5.  Serological tests for estimating the titers of antibody for infections such as toxoplasmosis, rubella, cytomegalovirus, herpes simplex (TORCH) and hepatitis B virus.

Treatment

1. no treatment is required if vision is goo

2. dilation with atropine untill puberty if cataract is small central

3. optical iridectomy if cataract is small central

4. lens aspiration with IOL implantation Paediatric cataracts are soft and can be aspirated through incisions that are 1–1.5 mm in size at the limbus 

5. lensectomy: lens along with anterior and posterior capsule and anterior vitrectomy is done using a vitreous cutter

complications of lensectomy and lens aspiration

1. posterior capsular opacification

2. secondary membranes

3. glaucoma

Visual Rehabilitation

i. Spectales—They are useful for older children with bilateral aphakia but not for unilateral aphakia.

ii. Contact lenses—These are superior optical solution for both bilateral and unilateral aphakia

iii. IOL implantation—These are increasingly being performed in young children and even infants, specially in unilateral cataract. The IOL should be of a single piece type, i.e. optic and haptic in one piece with diameter not more than 12 mm. It is fitted in the capsular bag in the posterior chamber. 

 Rigid IOL—One piece rigid IOL is made of polymethyl methacrylate (PMMA)

 Foldable IOL—It is hydrophobic, foldable, acrylic polymer lens

 Power of IOL—In children below 2 years, an undercorrection by 20% is recommended. In children between 2-8 years of age 10% undercorrection from the calculated biometric power is recommended to counter the ‘myopic shift’. emetropic power in children over 8 year is preferred

iv. Occlusion—Occlusion of better eye is done to treat or prevent amblyopia.