Congenital Glaucoma

Primary congenital glaucoma (PCG) is the commonest childhood glaucoma, resulting from isolated developmental abnormality of the trabecular meshwork (trabeculodysgenesis) and Schlemm canal causing impaired aqueous outflow.

• Incidence about 1 in 10,000 live births in Western populations, and as high as 1 in 2,500 in consanguineous populations (Middle East, Roma communities, Saudi Arabia). Boys account for about 65 percent; 75 percent bilateral.
• Mostly autosomal recessive (CYP1B1 gene mutations the commonest cause; LTBP2, TEK variants).
• Classification by age: newborn onset (birth to 1 month, about 25 percent, severe), infantile (1 to 24 months, about 60 percent, best prognosis), late recognised (after 24 months).
• Secondary childhood glaucomas: associated with other anomalies (aniridia, Axenfeld-Rieger syndrome, Peters anomaly, Sturge-Weber syndrome, neurofibromatosis, Marfan, homocystinuria), acquired (uveitis, steroid, trauma, retinopathy of prematurity, tumour), and after cataract surgery.

• Classic triad: epiphora (watering), photophobia and blepharospasm.
• Corneal enlargement (buphthalmos): horizontal corneal diameter over 12 mm at age 1 (normal 9.5 to 10.5 mm at birth, 10 to 11 mm at 1 year), corneal oedema and haze, and Haab striae (breaks in Descemet membrane, horizontal or curvilinear).
• Increased axial length, myopia, deep anterior chamber, optic disc cupping (large cup to disc ratio over 0.3 in infants, asymmetry), raised pressure (often 25 to 40 mmHg under examination; sedation and anaesthesia lower pressure artefactually).
• Fussy infants, poor feeding; late: amblyopia, strabismus, lens subluxation, and scleral thinning.
• Differential: nasolacrimal duct obstruction (no photophobia, normal cornea), megalocornea (normal pressure and stable), corneal dystrophies, birth trauma (breaks in Descemet vertical or oblique, uniocular), keratitis, and metabolic disease.

• Examination under anaesthesia (with ketamine or sevoflurane, noting that sevoflurane lowers pressure): intraocular pressure (Perkins, Tono-Pen or iCare), corneal diameter, gonioscopy (anterior insertion of iris, flat iris, absent angle landmarks, Barkan membrane), optic disc cup to disc ratio, axial length and pachymetry.
• Cycloplegic refraction. Photography of discs for monitoring.
• Systemic examination for associated syndromes (facial, cardiac, neurocutaneous), CYP1B1 genetic testing and family screening.
• Normal infant pressure is under about 15 mmHg; a diagnosis requires pressure above 21 mmHg with at least two other signs (corneal changes, disc cupping, axial length growth).

• Surgery is the primary treatment: goniotomy (clear cornea needed) or trabeculotomy (ab externo, or 360-degree suture or illuminated catheter assisted), with success rates of 80 to 90 percent in infants aged 3 to 12 months. Combined trabeculotomy trabeculectomy with mitomycin C 0.2 to 0.4 mg/mL for hazy corneas or severe disease, and repeat angle surgery if pressure remains raised.
• Refractory disease: trabeculectomy with mitomycin C, glaucoma drainage devices (Ahmed, Baerveldt), cyclophotocoagulation (transscleral diode, endoscopic).
• Medical therapy is a temporary measure before surgery or as adjunct: timolol 0.25 percent (0.5 percent in older children) twice daily with caution (bradycardia and bronchospasm in infants), dorzolamide 2 percent three times daily, latanoprost 0.005 percent nightly; brimonidine is contraindicated in infants and young children (apnoea, lethargy); oral acetazolamide 10 to 20 mg/kg/day in 3 divided doses pre-operatively.
• Visual rehabilitation: spectacles for high myopia and astigmatism, patching and amblyopia therapy, treat strabismus, contact lenses for aphakia.
• Lifelong follow up: pressure, discs, axial length, corneal diameter, and visual fields; relapse can occur years later. Counsel the family on recurrence risk (25 percent in autosomal recessive disease) and genetic testing.