Megalocornea

Megalocornea, also known as anterior megalophthalmos, X-linked megalocornea, and macrocornea, is a rare bilateral nonprogressive congenital defect that is characterized by an increased corneal diameter greater than 12.5 to 13 mm at birth and a deep anterior chamber with normal intraocular pressures. Thinning of the cornea has also been frequently associated. The defect falls under the category of anterior segment dysgenesis and is associated with several other conditions, including Axenfeld-Rieger syndrome, Peters anomaly, primary congenital glaucoma, aniridia, congenital hereditary endothelial dystrophy, and sclerocornea. In addition, it is a component of many different congenital syndromes. There are two patterns of clinical presentation. Primary megalocornea is an isolated megalocornea with no additional ocular or systemic manifestations. The second clinical presentation is megalocornea with other associated ocular and systemic abnormalities. This article will focus on primary congenital megalocornea (hereafter referred to as megalocornea) and will discuss possible comorbid conditions and syndromes in the ‘differential diagnosis’ section. Primary megalocornea was first described in 1869, but the genetic basis of this disease has only been elucidated in the past decade. The disease is usually inherited in an X-linked fashion, but other inheritance patterns have been described. The disease is generally asymptomatic in childhood though astigmatism from the large cornea may result in blurred vision. Adults may experience premature cataract formation, typically between the ages of 30 and 50, glaucoma, arcus juvenilis, lens subluxation, and mosaic corneal dystrophy. Other described comorbidities include iris atrophy, coloboma, abnormalities in zonular fibers, transillumination of the irides, lens dislocation, retinal detachment, and asymmetry in corneal size.