Congenital glaucoma

Description

Glaucoma may be classified into primary and secondary types. Most cases fall into the former group. Primary glaucoma may be further categorized as open angle, closed angle or congenital. Congenital glaucoma forms by far the minority of primary cases, and may itself be further subdivided into primary and secondary disorders. In primary congenital glaucoma, inappropriate development of angle structures leads to raised intraocular pressure, whereas secondary congenital glaucoma follows some other ocular or general condition. Congenital glaucoma occurs before the age of 2 years and most cases are bilateral. The presentation may be asymmetrical and unilateral cases have been reported. In the USA and Europe it is more common in males, whereas the opposite is the case in Japan. Multifactorial and autosomal recessive inheritance patterns have been proposed and, in many instances, the condition appears to be sporadic in nature.

Symptoms

The hallmark symptoms of congenital glaucoma are tearing and photophobia. If present to a marked degree, lacrimation may be misdiagnosed as being caused by an obstruction in the lacrimal drainage system.

Signs

Up to the age of 2 years, the sclera and cornea are far more distensible than in the adult eye. Whereas enlargement of the globe is rare in adult glaucomas, it is a cardinal sign in congenital glaucoma and is known as buphthalmos – literally ox eye. The eye’s outer coats stretch and thin as a result of high intraocular pressure, and a horizontal corneal diameter of 12 mm or more in an infant aged under 1 year should arouse suspicion. Splits in Descemet’s membrane (Haab’s striae) lead to corneal edema. These signs of a hazy cornea, together with an enlarged globe, make it more likely that advice will be sought rather than the symptoms of tearing and photophobia. Cupping of the optic disc may be present which can be reversible in the younger patient. Enlargement of the eye can cause high refractive errors and a myopic shift in refraction. Strabismus can occur when the glaucoma is unilateral or more advanced in one eye. In both situations, amblyopia may be the result.

Prevalence

It has been estimated that congenital glaucoma has an incidence of about 1 in 10,000 to 1 in 15,000 live births in the USA. Studies from other countries such as Northern Ireland and Saudi Arabia have indicated a lower and higher incidence respectively.

Differential diagnosis

Congenital X-linked recessive megalocornea; other causes of corneal edema and/or Haab’s striae, such as trauma from an instrument delivery and congenital hereditary endothelial dystrophy. When persistent lacrimation is present in infants, it must be distinguished from a canalicular or nasolacrimal duct obstruction.

Management

Incisional surgery The mainstay of treatment for congenital glaucoma is surgery. The procedures of choice are goniotomy and trabeculotomy. Filtering surgery, such as a trabeculectomy, may be used in older children. Medical management is rarely successful, but before surgery a topical P blocker or carbonic anhydrase inhibitor may be tried.

Refractive and low vision care As these eyes usually have high refractive errors, this needs correcting and any amblyopia must be aggressively treated. Frequent monitoring is required and, as with the initial examination, this may have to be undertaken under general anaesthesia. Life-long review is essential.