Primary Congenital Glaucoma: The Watering Baby Who Is Not Blocked

An infant who cries in bright light, waters constantly and screws their eyes shut is often assumed to have a blocked tear duct. Sometimes the pressure inside the eye is destroying the optic nerve.

Primary congenital glaucoma is raised intraocular pressure from a developmental abnormality of the aqueous drainage angle, present from birth or the first years of life.

An infant eye is elastic, so instead of simply cupping the disc, the whole globe stretches.

That stretching produces the signs that make this diagnosis possible from the end of the bed – an enlarged, cloudy cornea in a photophobic, watering baby.

Unlike adult glaucoma, this is a surgical disease from the outset; drops are a holding measure, not a treatment.

Recognising the classic triad and referring the same day is what preserves vision in these children.

What Is Primary Congenital Glaucoma?

Primary congenital glaucoma (PCG) is glaucoma resulting from isolated maldevelopment of the trabecular meshwork and anterior chamber angle, without other ocular or systemic anomalies.

It is classified by age at presentation:

Newborn or true congenital – present at birth, roughly a quarter of cases
Infantile – presenting between one month and two years, the largest group
Late-recognised or juvenile-onset – presenting after two years, when the globe is less elastic and enlargement is less prominent

The word “primary” is doing important work here – secondary childhood glaucomas from aniridia, Axenfeld-Rieger anomaly, Sturge-Weber syndrome or previous cataract surgery are managed differently and must be excluded.

Epidemiology

PCG is rare in absolute terms but is a leading cause of childhood blindness where it goes unrecognised.

The majority of cases present within the first year of life
Bilateral involvement occurs in most cases, though frequently asymmetric
Boys are affected more often than girls in most reported series
Incidence is considerably higher in populations with high rates of consanguineous marriage
Most cases are sporadic, but an autosomal recessive pattern with variable penetrance is well recognised, and CYP1B1 mutations are the most frequently implicated

Asymmetry is a diagnostic trap: a mildly affected fellow eye can look normal by comparison, so both eyes need measuring rather than comparing.

Pathophysiology

The disease is a failure of normal angle development, and the infant eye’s response to pressure is what shapes the clinical picture.

Maldevelopment of the trabecular meshwork and angle structures obstructs aqueous outflow
Intraocular pressure rises and, because the infant sclera and cornea are elastic, the whole globe enlarges – buphthalmos
Corneal enlargement stretches Descemet membrane until it splits, producing horizontal or curvilinear Haab striae
Breaks in Descemet membrane allow aqueous into the stroma, causing corneal oedema, haze and the photophobia and watering that dominate the presentation
Axial elongation produces progressive myopia and anisometropia
Sustained pressure damages the optic nerve, and infant discs can cup rapidly – though this cupping is partly reversible if pressure is controlled early

The reversibility of infant disc cupping is one of the genuinely encouraging features of this disease, and it is a direct argument for treating quickly.

Clinical Presentation

The Classic Triad

Epiphora – persistent watering
Photophobia – distress and eye closure in bright light
Blepharospasm – forced lid closure

These three symptoms in an infant should trigger a pressure check, not a diagnosis of blocked tear duct.

Examination Findings

Buphthalmos – a visibly enlarged eye, often asymmetric between the two sides
Corneal enlargement, with a horizontal diameter above roughly 12 mm in the first year being suspicious
Corneal oedema and haze, which can range from subtle to a completely opaque cornea
Haab striae – horizontal breaks in Descemet membrane, a highly specific sign
Raised intraocular pressure, remembering that general anaesthetic agents lower measured pressure
Optic disc cupping, often large and sometimes asymmetric
Deep anterior chamber and, on gonioscopy, a high, flat iris insertion

Haab striae are worth looking for specifically, because they distinguish glaucomatous corneal enlargement from other causes of a cloudy neonatal cornea.

Diagnostic Evaluation

Examination Under Anaesthesia

Most infants require examination under anaesthesia for reliable assessment
Intraocular pressure measurement, interpreted with the knowledge that most anaesthetic agents reduce it and may mask disease
Corneal diameter measurement in both eyes with callipers
Gonioscopy to assess angle structures and exclude secondary causes
Optic disc assessment and, where possible, photography for later comparison

Supporting Measurements

Axial length by ultrasound biometry – progressive elongation is a sensitive marker of ongoing pressure damage and of treatment failure
Cycloplegic refraction, which typically shows progressive myopia
Pachymetry, since corneal thickness influences pressure readings

Excluding Secondary Glaucoma

Careful examination for aniridia, Axenfeld-Rieger anomaly, Peters anomaly and the facial naevus of Sturge-Weber syndrome
Systemic and genetic assessment where a syndromic association is suspected

Serial axial length is one of the most useful follow-up measurements available in infants, because it tracks disease control even when pressure readings are unreliable.

Differential Diagnosis

Conditions that can mimic the presentation include:

Congenital nasolacrimal duct obstruction – watering and discharge, but no photophobia, normal corneal size and a clear cornea
Congenital corneal opacities – Peters anomaly, sclerocornea, congenital hereditary endothelial dystrophy
Birth trauma with forceps-related Descemet breaks – typically vertical or oblique, unlike the horizontal striae of glaucoma
Megalocornea – a large but clear cornea with normal pressure and no disc changes
Congenital rubella and metabolic causes of corneal clouding
High myopia with a large eye but normal pressure

The orientation of Descemet breaks is a genuinely useful discriminator: horizontal or curvilinear suggests glaucoma, vertical suggests forceps injury.

Management

Surgery Is Definitive

Angle surgery is first-line: goniotomy where the cornea is clear enough to visualise the angle, or trabeculotomy where it is not
Success rates for angle surgery in classic PCG are good, and the procedure may be repeated
Trabeculectomy with antimetabolite, or a glaucoma drainage device, for cases failing angle surgery
Cyclodestructive procedures are generally reserved for refractory disease or eyes with poor visual potential

Medical Therapy as a Bridge

Topical agents are used to lower pressure temporarily before surgery or to supplement incomplete surgical control
Beta-blockers require caution in infants because of the risk of apnoea and bradycardia
Brimonidine is contraindicated in infants and young children owing to the risk of CNS depression and apnoea
Carbonic anhydrase inhibitors, topical or systemic, are commonly used

Visual Rehabilitation

Correction of the myopia and anisometropia that follow axial elongation
Amblyopia therapy, which is frequently the limiting factor in the final visual result
Lifelong follow-up, since pressure can rise again years after apparently successful surgery

Even a perfectly controlled pressure produces a poor visual outcome if the resulting anisometropic amblyopia is not treated with equal commitment.

Prognosis

Outcomes have improved considerably with early angle surgery, but depend heavily on timing.

Children presenting between about three and twelve months with clear corneas generally have the best surgical prognosis
Presentation at birth with severe corneal clouding carries a poorer outlook
Optic disc cupping can partially reverse in infants once pressure is controlled, unlike in adults
Amblyopia from corneal scarring, anisometropia and induced myopia is a major cause of persistent visual loss even after successful pressure control
Lifelong monitoring is essential, as late pressure rise and progressive damage can occur years later

The recurring theme is that pressure control is necessary but not sufficient – the visual result is decided by refraction and amblyopia therapy over the following years.

References

Childhood Glaucoma Research Network. Classification of childhood glaucoma. Consensus series.
Yu Chan JY, Choy BNK, Ng ALK, Shum JWH. Review on the management of primary congenital glaucoma. Journal of Current Glaucoma Practice. 2015.
Ho CL, Walton DS. Primary congenital glaucoma: 2004 update. Journal of Pediatric Ophthalmology and Strabismus. 2004.
Primary Congenital Glaucoma. StatPearls, NCBI Bookshelf.
Primary Congenital Glaucoma. EyeWiki, American Academy of Ophthalmology.