Congenital cataract and glaucoma — formative SAQs

SAQ 1 (10 marks)

A 4-week-old term infant is found at a routine check to have a dense white opacity filling the pupil of the left eye with an absent red reflex; the right eye is normal. The parents ask what is wrong and whether it can wait. [11]

Question: (a) What is the finding and why is it urgent? (b) Outline the definitive management and the surgical time-window, and explain what the Infant Aphakia Treatment Study concluded about aphakia versus primary IOL. (c) What long-term complication must this child be watched for, and what determines the final visual outcome? (10 marks) [7]

Model answer

(a) The finding and its urgency (3 marks). The finding is leukocoria from a dense unilateral congenital cataract, with an absent red reflex. It is urgent for two reasons. First, the same white pupil reflex is produced by retinoblastoma, persistent fetal vasculature and retinal detachment, none of which the generalist can exclude — so this is a same-day or urgent paediatric ophthalmology referral. Second, a dense unilateral cataract causes deprivation amblyopia, and the critical period for unilateral deprivation is the first 6 to 8 weeks, so the clock is almost out: waiting is not safe. The red reflex is performed in a dimmed room, ophthalmoscope at arm's length, +0 to +2 dioptres, comparing both pupils. [11]

(b) Definitive management and the IATS (4 marks). Once retinoblastoma is excluded, the cataract is removed by lensectomy with anterior vitrectomy within the surgical window — by about 6 weeks for a dense unilateral cataract (ideally within the first 4 to 6 weeks). The Infant Aphakia Treatment Study randomised unilateral infantile cataract to contact-lens aphakia versus primary IOL and found no difference in visual acuity at around 4.5 years, but substantially more reoperations and more glaucoma with a primary IOL. The practical conclusion is that for an infant operated in the first months the eye is usually left aphakic and corrected with a contact lens, reserving IOL implantation for older infants and children where the glaucoma risk is lower. After surgery the child enters an amblyopia programme of full optical correction and patching of the better eye through the sensitive period. [5] [7]

(c) Long-term surveillance and outcome (3 marks). The child must be watched lifelong for glaucoma following cataract surgery (aphakic glaucoma) — the leading cause of late visual loss after a successful operation — because it is common, silent, and develops months to years later, with younger age at surgery, microcornea and primary IOL as the main risk factors. The final visual outcome is decided by laterality, density and axial position of the opacity, timing of surgery, and — most modifiable — compliance with patching and optical correction. Set the family's expectation that the operation is the start of treatment, not the end. [5]

SAQ 2 (10 marks)

Question: A 3-month-old boy has had a persistently watery right eye for six weeks; he now screws the eye shut outdoors and dislikes bright light. The right cornea is hazy and looks larger than the left. (a) What is the diagnosis, what is the mechanism, and which examination confirms it? (b) Outline the stepwise surgical management and the place of medical therapy. (c) Name a topical drug that is contraindicated in this age group and why. (10 marks) [2]

Model answer

(a) Diagnosis, mechanism and confirmation (3 marks). The diagnosis is primary congenital glaucoma (PCG): the triad of epiphora, photophobia and blepharospasm with a cloudy and enlarged cornea (buphthalmos). The mechanism is a developmental anomaly of the angle (trabeculodysgenesis) — a high flat iris insertion with abnormal membrane-like tissue over the trabecular meshwork — that resists aqueous outflow and raises intraocular pressure; the pressure stretches the elastic infant sclera and cornea (buphthalmos) and tears Descemet membrane into horizontal Haab striae. The diagnosis is confirmed at an examination under anaesthesia by the constellation of a raised pressure, an enlarged/oedematous cornea, Haab striae, optic-disc cupping and the gonioscopic angle anomaly. [2]

(b) Stepwise surgical management and medical therapy (4 marks). PCG is primarily surgical, because the defect is structural. First-line is angle surgery: goniotomy when the cornea is clear enough to visualise the angle, or trabeculotomy ab externo when it is too cloudy; increasingly a 360-degree circumferential trabeculotomy with an illuminated microcatheter is primary, as a 2026 meta-analysis showed higher success than traditional sectoral angle surgery. If pressure is uncontrolled, escalate to trabeculectomy with mitomycin C, then a glaucoma drainage device (Ahmed, Baerveldt, PAUL), and finally cyclophotocoagulation for refractory disease. Medical therapy (topical timolol 0.25%, dorzolamide, short-course oral acetazolamide 10 to 15 mg/kg/day) is only a temporising bridge or adjunct, not a cure. [8]

(c) The contraindicated drug (3 marks). Brimonidine is contraindicated in this age group. As an alpha-2 agonist it crosses the immature blood-brain barrier and causes central-nervous-system depression — apnoea, bradycardia, hypotension, hypothermia and somnolence — and is generally avoided in children under about 2 years or under 20 kg. After angle surgery a miotic such as pilocarpine 1 to 2% is the safe postoperative alternative when additional pressure control is needed. [2]