Congenital glaucoma (code 98976)
A rare eye disease characterized by high intraocular pressure. Clinically, there is an increase in eye volume often associated with corneal edema.
Summary
Epidemiology
Congenital glaucoma (CG) is the most common type of glaucoma in early childhood. The prevalence at birth is estimated at approximately 1 in 45,450 live births in Europe. Boys are more commonly affected than girls, and the disease is bilateral in 70 to 80% of cases.
Clinical
The diagnosis is made during the first year of life in nearly 80% of cases. It is defined by the classic triad of epiphora, blepharospasm, and photophobia. Affected children have watery and red eyes, corneal opacity, and increased eye volume resulting from stretching of the immature eye due to increased intraocular pressure. Children over the age of 3 experience progressive myopia and insidious visual field loss.
Etiology
The etiology remains poorly understood, but the disease is thought to be caused by obstruction of the outflow of aqueous humor in the iridocorneal angle at the level of the trabecular meshwork. Genetic mapping of affected families has identified three chromosomal loci, GLC3A at 2p22.2, GLC3B at 1p36, and GLC3C at 14q24.3-q31.1, with mutations in the CYP1B1 gene (at 2p22.2) located at GLC3A. Mutations in the LTBP2 (in 14q24.3) and MYOC (in 1q23-q24) genes have also been identified.
Diagnostic method(s)
The diagnosis is based on a comprehensive ophthalmological examination revealing an opaque cornea with increased diameter and Haab’s streaks, elevated intraocular pressure (IOP) (a pressure greater than 20 mmHg or an asymmetry of more than 5 mmHg is a warning sign), a deep anterior chamber, anteriorly inserted iris, incomplete development of the scleral spur (analysable by gonioscopy), a high ratio between the diameter of the excavation (C for cup) and the diameter of the papilla (D for disc) of the optic nerve head, and myopia and astigmatism revealed by a refraction test. An examination under anesthesia may be performed if necessary.
Differential diagnosis
The differential diagnosis for redness and watery eyes is obstruction of the lacrimal duct, conjunctivitis, corneal abrasion, and uveitis, and for enlarged cornea, high axial myopia and megalocornia. The differential diagnosis of corneal opacity and edema aims to rule out congenital corneal dystrophies, trauma during birth, keratitis, congenital eye abnormalities, or storage diseases, while that of papillary excavation aims to rule out physiological excavation, papillary coloboma, genetic optic atrophy, and optic nerve hypoplasia.
Prenatal diagnosis
Prenatal diagnosis can determine the risk of the disease when the mutation is known in the family.
Genetic counseling
Most cases are sporadic, with approximately 10% of cases showing autosomal recessive transmission and variable penetrance. In the case of autosomal recessive transmission, genetic counseling should be offered to at-risk couples (both parents are carriers of a causal mutation) to inform them that there is a 25% risk of having an affected child in each pregnancy.
Management and treatment
Congenital glaucoma is mainly treated surgically, with medication playing only a supporting role. Initially, angle surgery (such as goniotomy or trabeculotomy), trabeculectomy, or deep sclerectomy is usually performed. The choice depends on the severity of the glaucoma and the surgeon’s preferences. Glaucoma drainage devices and diode laser cyclophotocoagulation are used in refractory cases. Amblyopia, corneal scarring, and cataracts are late complications. Early visual rehabilitation is important to prevent amblyopia. Patients may require regular follow-up throughout their lives to monitor IOP.
Prognosis
The prognosis is closely related to the time of onset of the disease; early diagnosis and prompt surgical treatment contribute significantly to visual improvement. Pressure is well controlled in most patients treated successfully during early childhood who maintain stable optic nerves and a fully functional visual field into adulthood.