Q5 LONG ANSWER 10M ★ High-yield

Describe congenital and developmental cataract with its causes and management.

Ophthalmology · 3rd Professional

Congenital and developmental cataract is a leading cause of treatable childhood blindness, and the outcome depends almost entirely on how early it is detected and operated
Aetiology, in thirds — about a third are hereditary, autosomal dominant, and bilateral; about a third are associated with a systemic or metabolic disorder; and about a third are idiopathic — a proportion which is higher among unilateral cases, most of which are sporadic and isolated

Cause	Features
Intrauterine infection — rubella	The classical cause. A dense, pearly white nuclear cataract, often bilateral, from infection in the first trimester. Accompanied by microphthalmos, "salt-and-pepper" retinopathy, glaucoma, deafness, patent ductus arteriosus and pulmonary stenosis, and developmental delay. The virus persists IN the lens for years, so surgery may provoke a severe inflammatory reaction. Entirely preventable by rubella immunisation.
Other torch agents	Toxoplasmosis, cytomegalovirus, herpes simplex, varicella and syphilis
Galactosaemia	Deficiency of galactose-1-phosphate uridyl transferase; galactitol accumulates osmotically, giving a central "oil droplet" appearance. Critically, it is reversible if a galactose-free diet is started early — one of the very few cataracts that can be treated medically. Accompanied by failure to thrive, hepatomegaly, jaundice and E. Coli sepsis
Other metabolic	LOWE (oculocerebrorenal) syndrome — cataract, glaucoma, renal tubular acidosis and hypotonia; hypoglycaemia; hypocalcaemia; mannosidosis; and Fabry disease
Chromosomal	Down syndrome (trisomy 21); trisomy 13 and 18; Turner syndrome
Systemic syndromes	Myotonic dystrophy (Christmas-tree cataract); Alport syndrome (anterior lenticonus.
Ocular associations	Persistent fetal vasculature (persistent hyperplastic primary vitreous), aniridia, coloboma, retinopathy of prematurity, and microphthalmos

Morphological type	Features
Lamellar (zonular)	The commonest developmental cataract. A discrete opaque zone surrounding a clear nucleus, with clear cortex outside it, and with linear opacities called riders extending onto the equator. Reflects a transient insult at a particular stage of development. Bilateral and symmetrical, often dominantly inherited
Nuclear	Dense central opacity; classical of rubella; causes profound early deprivation
Polar — anterior	small, stationary and visually insignificant; associated with persistent pupillary membrane. A pyramidal anterior polar cataract projects into the anterior chamber and causes anisometropic amblyopia
Polar — posterior	More significant, being in the visual axis; and important surgically because the posterior capsule beneath it is often deficient.
Sutural, coronary, blue-dot (cerulean)	Usually visually insignificant and non-progressive
Total and membranous	Dense; membranous cataract results from resorption of lens matter leaving the capsules apposed

Screening — the red reflex test should be performed on every newborn and at every routine child check. The bruckner test (comparing the two red reflexes simultaneously with a direct ophthalmoscope from a metre away) detects asymmetry from a cataract, a refractive error, a squint or a tumour, and takes seconds
Assessment of visual significance — a cataract is significant if it is central and more than 3 mm, or dense enough to obscure the fundus view; and the surest sign in an infant is a poor fixation response, nystagmus or a squint
Examination — both eyes dilated; a search for microphthalmos, glaucoma, PFV, coloboma and retinal disease; measurement of axial length and keratometry; and B-scan where the fundus cannot be seen

Timing IS everything, and it is determined by deprivation amblyopia. The critical period for visual development begins at 6 weeks of age, when fixation matures, and the outcome falls steeply with delay beyond it
Unilateral dense cataract — operate by about 4 to 6 weeks. The prognosis is worse than for bilateral disease, because the good eye competes and suppression is profound; and aggressive occlusion therapy afterwards is essential and is what actually determines the result
Bilateral dense cataract — operate by about 8 to 10 weeks, the second eye within a week or two of the first, or under the same anaesthetic in some protocols

Situation	Timing and reasoning
Unilateral dense cataract	Operate by 4 to 6 weeks. The prognosis is the worst of any group.
Bilateral dense cataract	Operate by 8 to 10 weeks, the second eye within a week or two. The prognosis is better than for unilateral disease.
Partial or non-axial opacity	Observe with dilating drops and optical correction; operate only if vision or fixation deteriorates
Later-onset developmental cataract	Less urgent, since the critical period is past and deprivation amblyopia is far less dense
Intraocular lens under 2 years	avoided — the infant aphakia treatment study found no visual benefit and more complications; a contact lens is used instead
Intraocular lens over 2 years	Standard, with the power chosen to allow for the myopic shift as the eye grows — so the child is left deliberately hypermetropic at first
Lifelong follow-up	For aphakic glaucoma, which affects a substantial proportion, may appear years later and is silent; and for refractive change and strabismus

Check the red reflex in every newborn; it is the only screening test for congenital cataract and for retinoblastoma, it takes seconds, and it is frequently omitted
Treat leucocoria as retinoblastoma until proved otherwise, and arrange urgent dilated examination and B-scan
Operate a dense unilateral cataract by 6 weeks; every week of delay costs vision, and referral must be immediate rather than routine

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