Congenital cataract and glaucoma — branching viva

Opening (examiner)

A 4-week-old term infant is referred by the child-health nurse because the left pupil looked white. On your red-reflex test the left reflex is absent. The right eye is normal. Take me through your assessment and your immediate management. [11]

Branch 1 — the red reflex and the urgency

Model answer. I perform the red reflex in a dimmed room, ophthalmoscope at about half a metre, large spot, focussing ring at roughly 0 to +2 dioptres, comparing both pupils. An absent, darkened, whitened or asymmetric reflex is abnormal. The immediate action is a same-day or urgent paediatric ophthalmology referral, because a white pupil reflex is produced by a dense cataract but also by retinoblastoma, persistent fetal vasculature and retinal detachment — I cannot exclude those at the bedside. For a confirmed dense unilateral cataract the amblyopia clock is almost out: the unilateral critical period is the first 6 to 8 weeks, so I refer now, not at the next visit. [11] [12]

Examiner probe: "What exactly is deprivation amblyopia, and why is the unilateral critical period so short?" A dense cataract denies the visual cortex a sharp image during the period it is refining its connections. The cortex keeps the inputs that carry a sharp, matched picture and prunes those that do not; a deprived eye is permanently weakened. In a unilateral cataract the better eye wins the cortical competition and suppresses the deprived one, so the harm accrues in weeks; a bilateral dense cataract is less competitive but still amblyopic and produces a searching sensory nystagmus by 2 to 3 months. [5]

Branch 2 — the surgical decision

Examiner: "The cataract is confirmed and dense. When do you operate, and do you implant a lens?" [5]

Model answer. The operation is lensectomy with anterior vitrectomy within the surgical window — by about 6 weeks for a dense unilateral cataract (ideally the first 4 to 6 weeks), and for a dense bilateral cataract by about 6 to 10 weeks, operating the second eye within a week or two of the first. On the lens question I apply the Infant Aphakia Treatment Study: it randomised unilateral infantile cataract to contact-lens aphakia versus primary IOL and found no difference in acuity at about 4.5 years, but more reoperations and more glaucoma with a primary IOL. So for an infant operated this young I would expect the eye to be left aphakic and corrected with a contact lens, with a secondary IOL considered later in childhood. After surgery the family enters an amblyopia programme of optical correction and patching the good eye. [5]

Examiner probe: "What determines the final acuity?" Laterality, the density and axial position of the opacity, the timing of surgery, and — most modifiable and most decisive — compliance with patching and glasses. The operation is the start of treatment, not the end. [5]

Branch 3 — the long-term complication

Examiner: "The operation goes well. What do you watch for over the next ten years?" [5]

Model answer. Glaucoma following cataract surgery (aphakic glaucoma) — the leading cause of late visual loss after a successful operation. It is common, silent, and develops months to years later, and the dominant risk is younger age at surgery, with microcornea and primary IOL as additional risks. So this child needs lifelong intraocular-pressure surveillance at every visit, with disc review and refraction. I would also watch for visual-axis opacification and strabismus. [5]

Branch 4 — branching into glaucoma

Examiner: "Now picture a different child: a 3-month-old with a tearing right eye who screws it shut in bright light, and the cornea looks large and hazy. What is this, and how do you confirm it?" [2]

Model answer. That is the primary congenital glaucoma triad of epiphora, photophobia and blepharospasm, with a cloudy, enlarged cornea (buphthalmos). The corneal enlargement happens only in infancy because the sclera is elastic. I confirm the diagnosis at an examination under anaesthesia by the constellation of a raised pressure, an enlarged or oedematous cornea, horizontal Haab striae, optic-disc cupping and a high flat iris insertion on gonioscopy. I would not be reassured by a single normal pressure reading, because anaesthesia distorts it. [2]

Examiner probe: "Outline the surgical ladder, and the place of drops." First-line is angle surgery — goniotomy if the cornea is clear, trabeculotomy ab externo if it is cloudy; increasingly a 360-degree circumferential trabeculotomy with an illuminated microcatheter is primary, as a meta-analysis showed higher success than sectoral angle surgery. If uncontrolled, escalate to trabeculectomy with mitomycin C, then a glaucoma drainage device, then cyclophotocoagulation. Drops (timolol 0.25%, dorzolamide, short-course acetazolamide 10 to 15 mg/kg/day) are only a temporising bridge or adjunct — the defect is structural and only surgery restores outflow. [8]

Branch 5 — the drug trap

Examiner: "You are asked to start a drop before surgery. Is there any agent you would refuse to use in this baby?" [2]

Model answer. Brimonidine. It is an alpha-2 agonist that crosses the immature blood-brain barrier and causes CNS depression — apnoea, bradycardia, hypotension, hypothermia and somnolence — and is generally contraindicated under about 2 years or under 20 kg. A safe alternative pressure-lowering approach in an infant is timolol 0.25% (cautiously, avoiding asthma and heart block) with dorzolamide, and after the angle is opened a miotic such as pilocarpine 1 to 2%. [2]

Closing

Examiner: "Summarise the general paediatrician's role in one sentence." Perform a competent red-reflex test at every newborn and infant contact, recognise the glaucoma triad in the tearing, light-averse infant, and refer both urgently — then hold the long view on patching and lifelong pressure surveillance, because the operation is the beginning of care, not its end. [11]