What are the main diagnostic methods for primary congenital glaucoma in an infant presenting with excessive tearing, photophobia, corneal haze, and an enlarged globe?

Diagnostic Methods for Primary Congenital Glaucoma

Primary congenital glaucoma is diagnosed through a combination of clinical examination findings—including buphthalmos, corneal edema, photophobia, and excessive tearing—along with measurement of elevated intraocular pressure and examination under anesthesia when necessary. 1, 2

Clinical Presentation and Key Symptoms

The classic triad of symptoms that should prompt immediate evaluation includes:

• Excessive tearing (epiphora) caused by corneal changes secondary to elevated intraocular pressure 2, 3
• Photophobia and blepharospasm resulting from corneal edema and irritation 2, 4
• Eye rubbing and irritability in infants who cannot verbalize discomfort 4

These symptoms typically present between 2 months and 2-3 years of age, though onset can occur at birth 2, 3

Essential Physical Examination Findings

External Examination

The external examination must assess for the hallmark signs of congenital glaucoma 1:

• Buphthalmos (enlarged globe) detected by comparing globe position when viewing from above the infant's head 1
• Increased corneal diameter beyond normal age-appropriate measurements 1, 4
• Assessment of head position for compensatory posturing 1

Anterior Segment Examination

Slit-lamp biomicroscopy or hand-held examination devices are critical for identifying 1:

• Corneal edema and clouding visible even without magnification in advanced cases 1, 2
• Haab's striae (horizontal breaks in Descemet's membrane) pathognomonic for congenital glaucoma 3, 4
• Anterior chamber depth assessment to evaluate angle anatomy 1

For infants and uncooperative young children, anterior segment examination can be performed using a direct ophthalmoscope, magnifying lens for indirect ophthalmoscopy, or hand-held slit-lamp biomicroscope 1

Intraocular Pressure Measurement

Intraocular pressure measurement is mandatory whenever a child presents with signs or risk factors for glaucoma 1:

• Portable instruments including Tono-Pen, Perkins tonometer, and iCare rebound tonometer facilitate IOP testing in children 1
• Examination under anesthesia (EUA) is often required for accurate IOP measurement and comprehensive evaluation when office examination is inadequate 1, 3
• Serial measurements during EUA allow documentation of IOP trends and response to treatment 3

The American Academy of Ophthalmology notes that while IOP measurement is not routine for every child, it should be performed whenever glaucoma is suspected based on clinical manifestations such as buphthalmos, epiphora, photosensitivity, and corneal clouding 1

Additional Diagnostic Measurements

Corneal Assessment

• Corneal diameter measurement to document enlargement beyond age-appropriate norms 4
• Central corneal thickness measurement may aid in assessment of suspected or known glaucoma 5

Axial Length and Refractive Error

• Increased axial length documented through biometry 4
• Progressive myopia in very young children may indicate uncontrolled glaucoma 1
• Cycloplegic refraction to assess for high myopia associated with globe enlargement 1

Optic Nerve Evaluation

Fundus examination must document 1:

• Enlarged optic nerve cup-to-disc ratio compared to age-matched norms 1, 3
• Asymmetry between eyes in unilateral or asymmetric cases 3
• Progressive cupping with serial examinations indicating inadequate IOP control 1

Examination Under Anesthesia Protocol

When office examination is insufficient, EUA provides comprehensive evaluation 1, 3:

• IOP measurement before anesthetic agents that may artificially lower pressure 1
• Corneal diameter and clarity assessment with precise measurements 3, 4
• Gonioscopy to evaluate angle anatomy and identify trabecular meshwork abnormalities 2, 4
• Optic nerve examination with detailed cup-to-disc ratio documentation 3
• Axial length measurement via A-scan biometry 4

Diagnostic Pitfalls to Avoid

Do not dismiss unilateral presentation or absence of classic symptoms—primary congenital glaucoma can present atypically without the full triad of tearing, photophobia, and blepharospasm 3. One case report documented a child initially diagnosed with megalocornea who was later found to have primary congenital glaucoma only after Haab's striae appeared and IOP elevation was documented on repeat EUA 3.

Serial examinations are essential because initial findings may be equivocal, and progression of corneal changes, IOP elevation, or optic nerve cupping may only become apparent over time 3.

The histopathology confirms variable trabecular meshwork anomalies without an imperforate membrane, distinguishing primary congenital glaucoma from other childhood glaucomas 2. Thorough examination is necessary to differentiate primary congenital glaucoma from secondary forms and syndromic glaucomas 2, 6.

Advanced imaging including optical coherence tomography may play an important role in assessment, though brain MRI is not routinely indicated unless neurological abnormalities are suspected 5, 6.