Primary Congenital Glaucoma Classification
Primary congenital glaucoma is an open-angle disease characterized by developmental anomalies of the trabecular meshwork and anterior chamber angle that obstruct aqueous outflow despite the angle remaining anatomically open. 1, 2
Anatomic Classification
Primary congenital glaucoma (PCG) presents with open anterior chamber angles on gonioscopic examination, distinguishing it fundamentally from angle-closure mechanisms. 3, 1 The pathophysiology involves:
- Trabeculodysgenesis: A congenital anomaly of the trabecular meshwork and anterior chamber angle structures that impedes aqueous humor drainage while maintaining an open angle configuration 1
- Developmental obstruction: The trabecular meshwork itself is malformed, creating resistance to outflow without physical angle closure 1, 2
Key Diagnostic Features
When evaluating a child with suspected PCG during examination under anesthesia:
- Gonioscopy is mandatory to verify open anterior chamber angles and assess trabecular meshwork anatomy for surgical planning 3
- The angle remains open throughout the disease course, unlike primary angle-closure glaucoma where the peripheral iris blocks the trabecular meshwork 4
- Look for characteristic signs including corneal enlargement, elevated intraocular pressure, and optic nerve cupping 1, 2
Clinical Distinction from Adult Glaucoma
This differs critically from adult primary open-angle glaucoma in several ways:
- Age of onset: PCG presents in infancy (most commonly under 30 days of age), whereas adult POAG has adult onset 5, 6
- Mechanism: PCG involves congenital maldevelopment of angle structures, while adult POAG represents acquired progressive optic neuropathy 5, 1
- Genetics: PCG frequently involves autosomal recessive inheritance (particularly CYP1B1 gene mutations), whereas adult POAG has more complex polygenic patterns 7
Important Clinical Pitfalls
Do not confuse "open angle" with normal angle anatomy—in PCG the angle is open but structurally abnormal with trabeculodysgenesis preventing normal aqueous drainage. 1 This is why:
- Medical therapy plays only a supportive role in PCG 1
- Surgical intervention (goniotomy or trabeculotomy) is the definitive treatment, unlike adult POAG where medical therapy is often first-line 1, 6
- Prognosis depends heavily on timing of initial presentation and surgical intervention, with earlier presentation generally indicating worse outcomes 1
Classification Within Childhood Glaucomas
PCG represents a primary childhood glaucoma (not secondary to other ocular or systemic conditions), distinguished from juvenile open-angle glaucoma (JOAG) by age of onset and from secondary childhood glaucomas associated with Axenfeld-Rieger anomaly, Peters anomaly, aniridia, or systemic syndromes. 8