Congenital glaucoma (ORPHA:98976)
A rare ophthalmic disorder characterized by an elevated intra-ocular pressure. The clinical presentation frequently associates an increase in the size of the eye, as well as corneal edema.
Epidemiology
Congenital glaucoma (CG) is the most common glaucoma of infancy. The birth prevalence is estimated at around 1/45,450 live births in Europe. Males are more commonly affected than females and the disease is bilateral in 70 to 80% cases.
Clinical description
Diagnosis is made in the first year of life in about 80% of cases. The classic triad includes epiphora, blepharospasm and photophobia. Affected children are noted as having red watery eyes, cloudy corneas and ocular enlargement, caused by stretching of the immature eye due to elevated intraocular pressure. Children older than 3 years develop progressive myopia and insidious field loss.
Etiology
Etiology is poorly understood but the obstruction to the aqueous outflow seems to occur at the iridocorneal angle and at the level of the trabeculum. Gene mapping of affected families has identified three chromosomal loci, GLC3A in 2p22.2, GLC3B in 1p36 and GLC3C in 14q24.3-q31.1 of which, the CYP1B1 gene (2p22.2) on GLC3A harbors mutations. Mutations in LTBP2 (14q24.3) and MYOC (1q23-q24) genes have also been identified.
Diagnostic methods
Diagnosis is made by a complete ophthalmologic examination, which reveals a hazy cornea of increased size and presence of Haab's striae, increased intraocular pressure (IOP) (more than 20 mm Hg or asymmetry of more than 5 mm Hg is of concern), deep anterior chamber, abnormally high insertion of iris, poorly developed scleral spur (with gonioscopy), increased cup to disc ratio of the optic nerve head and refraction testing showing myopia and astigmatism. Examination under anesthesia is done if necessary.
Differential diagnosis
The differential diagnoses for red watery eyes include nasolacrimal duct obstruction, conjunctivitis, corneal abrasion and uveitis while those for corneal enlargement include high axial myopia and megalocornea. The differential diagnoses for corneal clouding and edema include congenital corneal dystrophies, birth trauma, keratitis, congenital ocular anomalies or storage diseases while those for optic nerve cupping include physiologic cupping, coloboma of optic papilla, genetic optic atrophy and optic nerve hypoplasia.
Antenatal diagnosis
Prenatal diagnosis can determine the risk of the disease in families with known mutations.
Genetic counseling
Most cases are sporadic, in about 10% of cases autosomal recessive inheritance is seen with variable penetrance. In the case of an autosomal recessive inheritance, genetic counseling should be offered to at-risk couples (both individuals are carriers of a disease-causing mutation) informing them that there is a 25% risk of having an affected child at each pregnancy.
Management and treatment
Congenital glaucoma is primarily managed surgically, with medical therapy playing only an adjunctive role. At first, it is usually practiced angle surgery (such as goniotomy or trabeculotomy), trabeculectomy or deep sclerectomy The choice depends on the severity of the glaucoma and the surgeon's habits Glaucoma drainage devices and diode laser cyclophotocoagulation are used in refractory cases. Amblyopia, corneal scarring and cataract are late complications. Early visual rehabilitation is important to prevent amblyopia. Patients may need regular life-long follow up to monitor IOP.
Prognosis
Prognosis is largely related to the timing of presentation; early diagnosis and prompt surgical treatment significantly influences the visual outcome. Most patients successfully treated in infancy maintain good pressure control with stable optic nerves and fully functional visual fields into adulthood.

                            Last update: 
                            April 2020


                            - Expert reviewer(s): 
                            Dr Emmanuel MARCIANO