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OP7.1 | Congenital Glaucoma — SDL Guide (Part 2)

Diagnosis and Differentials

The diagnosis of primary congenital glaucoma rests on the combination of clinical features (the classic triad), physical signs (buphthalmos, Haab striae), and the EUA findings (raised IOP, enlarged corneal diameter, trabeculodysgenesis on gonioscopy, increased C:D ratio, and globe enlargement on biometry). There is no single pathognomonic test; the diagnosis is syndromic — a clinical gestalt requiring all findings in context. The constellation must be interpreted together: an infant with epiphora alone may simply have nasolacrimal duct obstruction; the same infant with photophobia, blepharospasm, a corneal diameter exceeding 12 mm, and a hazy cornea demands urgent ophthalmological assessment under anaesthesia. Gonioscopy under EUA seals the diagnosis by directly demonstrating the trabeculodysgenesis — the undifferentiated angle tissue or high iris insertion that is pathognomonic of PCG. Secondary causes of congenital glaucoma (associated with Sturge-Weber syndrome, aniridia, Axenfeld-Rieger spectrum, or congenital rubella) must also be excluded by the presence or absence of systemic or ocular anomalies beyond the angle maldevelopment itself.

The most important and most common diagnostic pitfall is misattributing epiphora to nasolacrimal duct obstruction (NLDO). NLDO is extremely common in neonates (occurring in up to 20% of infants) and also causes watering eyes. The key differentiators are:
- NLDO: IOP normal; cornea clear and normal-sized; no photophobia; regurgitation of mucopurulent discharge on sac massage (Crigler manoeuvre positive); typically resolves spontaneously by 12 months.
- PCG: IOP elevated; cornea enlarged and hazy; photophobia and blepharospasm present; no mucopurulent discharge.

Other important differentials include:

Condition	Key Differentiating Feature	IOP	Cornea	Treatment
Nasolacrimal duct obstruction	Mucopurulent discharge; sac massage reflux; normal cornea	Normal	Clear, normal size	Massage ± probing at 12 mo
Peters anomaly	Central corneal leukoma from birth; posterior corneal defect on slit-lamp	Variable	Opaque centrally, may be small	Penetrating keratoplasty
Sclerocornea	White scleralisation of cornea; typically small eye	Normal	Opaque white periphery	Keratoplasty
Congenital rubella	Maternal rubella history; systemic features; cataract	May be ↑	May be hazy (cataract or keratitis)	Anti-VEGF / cataract + secondary glaucoma Rx
Megalocornea	Large cornea but NO raised IOP; X-linked; clear cornea	Normal	Clear, large	Reassurance + refraction
Anterior uveitis	Ciliary flush; keratic precipitates; no buphthalmos	May be ↑	KPs, flare	Steroids + treat cause

Secondary congenital glaucoma should be considered when there are associated systemic or ocular anomalies: port-wine stain (Sturge-Weber), absence of iris (aniridia — associated with Wilms tumour via PAX6 deletion, requires renal screening), or structural ocular anomalies of the Axenfeld-Rieger spectrum.

Management: Surgery Is First-Line

The fundamental principle of managing primary congenital glaucoma is that surgery is the treatment of choice — not medical management. This contrasts sharply with adult primary open-angle glaucoma, where topical medications are the first-line approach. In PCG, the underlying defect is mechanical (dysplastic angle tissue obstructing outflow), and no medication can correct a structural maldevelopment. Medical therapy with topical drops (timolol, dorzolamide, latanoprost) can temporarily lower IOP and reduce corneal oedema to improve surgical visibility, but drugs are a bridge to surgery, not definitive treatment. Furthermore, systemic absorption of topical medications is proportionally much greater in infants than adults (relative to body weight), making systemic side effects (bradycardia from timolol, hypokalaemia from dorzolamide) a genuine safety concern.

The two classical surgical procedures are:

1. Goniotomy: A surgical incision is made through the trabecular meshwork under direct gonioscopic visualisation (using a Koeppe or Swan-Jacob lens), using a goniotomy knife inserted through a clear corneal incision. The incision opens the obstructed angle, allowing aqueous to drain into Schlemm's canal. Goniotomy is the preferred procedure when the cornea is clear enough to allow gonioscopic visualisation. Success rates exceed 80–90% for the initial procedure in PCG.

2. Trabeculotomy: A trabeculotome probe is passed externally (from the episcleral venous system) to locate Schlemm's canal, and then rotated inward to tear through the trabecular meshwork. This approach is preferred when the cornea is too hazy for gonioscopy. The external approach (ab externo) allows access to the drainage system without requiring a clear corneal view. In India and in resource-limited settings, trabeculotomy combined with trabeculectomy ('trabeculectomy-trabeculotomy') is widely performed.

If goniotomy/trabeculotomy fails (which occurs in more severe or late-presenting cases), options include:
- Repeat angle surgery (a second goniotomy/trabeculotomy is attempted before abandoning this approach)
- Trabeculectomy (filtering surgery creating a subconjunctival bleb) with antimetabolites (mitomycin C — MMC) in children
- Glaucoma drainage devices (Ahmed/Molteno implants) for refractory cases
- Cyclodestructive procedures (cyclocryotherapy, cyclophotocoagulation) as a last resort

Post-operative management is equally important: IOP normalisation allows the corneal oedema to clear, and the optic disc cupping may partially reverse in infants (unlike adults). However, amblyopia management is critical — the child requires aggressive optical rehabilitation (spectacles for myopia from axial elongation, patching for amblyopia in the fellow eye) to achieve useful vision. The visual prognosis depends heavily on the degree of optic nerve damage at presentation and the success of amblyopia therapy.

Key management principles summary:
- Surgery is first-line (not medications)
- Goniotomy (clear cornea) or trabeculotomy (hazy cornea) are the angle surgery options
- Medical therapy is temporary adjunct only
- Amblyopia management is mandatory post-operatively
- Disc cupping can reverse in infants after IOP control

Self-Assessment: Clinical Reasoning in Congenital Glaucoma

Having worked through the clinical presentation, anatomy, examination, and management of primary congenital glaucoma, you are now in a position to integrate this knowledge as a clinician would — connecting the molecular defect to the bedside decision. The following scenarios test your ability to apply the framework rather than simply recall facts.

Consider an infant presenting at 6 weeks of age with unilateral epiphora and a corneal diameter of 13 mm in the right eye only. Is this reassuring because only one eye is affected? No — unilateral PCG is a recognised presentation, and the need for EUA and goniotomy is no less urgent. Unilateral cases may be missed longer because parents and clinicians expect bilateral disease. The optic nerve in the affected eye may already show cupping by the time of diagnosis.

Consider a child who had successful goniotomy at 3 months of age and has maintained IOP below 18 mmHg for two years, but whose visual acuity at age 2 years is only 6/60 in the operated eye despite a clear cornea. What is the most likely cause? Amblyopia — the corneal haze during the critical window of visual cortex development (birth to age 7–8) creates deprivation amblyopia. IOP control was achieved but amblyopia therapy (patching the fellow eye, optical rehabilitation with spectacles for induced myopia from axial elongation) was either started late or was insufficient. This reinforces the teaching that surgical success in PCG is necessary but not sufficient — post-operative amblyopia management is the second battle.

Consider a family where the first child had PCG requiring bilateral goniotomy. The parents are now expecting their second child and ask: 'What is the chance this baby will also have it?' Given the autosomal recessive inheritance pattern (CYP1B1 mutations in familial PCG), each sibling of an affected child has a 25% risk of inheriting both mutated alleles and developing PCG. Neonatal screening of this infant — with ophthalmological assessment in the first week of life — is justified and can allow earlier surgical intervention before significant corneal or optic nerve damage has occurred.