History
The classic triad of manifestations in an infant or young child, any one of which should arouse suspicion of glaucoma, includes epiphora, photophobia, and blepharospasm.
Physical
Complete ophthalmologic examination
Large corneal diameters or increases in corneal diameters within the first few years of life provide strong additional support for the diagnosis of congenital glaucoma.
The average horizontal corneal diameter at birth is less than 10.5 millimeters. Distention of the globe in response to elevated intraocular pressure leads to enlargement of the cornea. If the measurement from corneoscleral junction horizontal to the opposing corneoscleral junction is more than 12 in the first year of life, it is highly suggestive of glaucoma. Grossly, this is more evident in asymmetric cases. Enlargement of the globe is called buphthalmos.
Corneal edema may be a direct result of the elevated intraocular pressure, producing a corneal haze that clears with normalization of the pressure. Haab striae represent tears in the Descemet membrane as a result of elevated intraocular pressure. In advanced cases, a dense opacification of the corneal stroma may occur secondary to the corneal edema, and it may persist, despite reduction of the intraocular pressure.
The early presence of glaucoma may deepen the anterior chamber. Because of the frequent occurrence of iris abnormalities in many types of both primary and secondary childhood glaucomas, the iris and angles always should be studied carefully and with thorough gonioscopy.
By the time that glaucoma is diagnosed in a child, the optic nerve head is usually abnormal. Variable cupping is present, usually annular in form, with nasalization of vessels and initial preservation of the well-vascularized rim. Optic nerve pallor is first seen temporally and represents an advanced stage of the disease.
Tonometry in the office setting often can be accomplished in a child's eye with a handheld instrument, such as a Perkins tonometer or a Tono-Pen. Accuracy of intraocular pressure measurements taken in the office may be artificially elevated from struggling on the part of the restrained infant.
Causes
Most cases of primary congenital glaucoma are sporadic in occurrence. However, evidence suggests that some cases of the disease may be transmitted through an autosomal recessive pattern, with variable penetrance, or a polygenic inheritance pattern. Polygenic inheritance is glaucoma resulting from the interaction of 2 or more nonhomologous genes. This has been shown in humans for the CYB1B1 and MYOC gene loci and in the mouse for CYP1B1 and FOXC1. [1]
CYP1B1, (locus GLC3A) the gene encoding cytochrome P4501B1 (P450, family I, sub family B, polypeptide 1) is associated with primary congenital glaucoma. GLC3B located on band 1p36 and GLC3C located on band 14q24.3 are loci that are linked to primary congenital glaucoma.
The incidence of CYP1B1 in familial cases is 93% in Saudi Arabia, 50% in Brazil, and 20-30% in ethnically mixed populations, and its incidence in nonfamilial (simplex) cases is 10-15%. Mice with this defect have structural abnormalities of the aqueous drainage system resembling those seen in humans.
