History
Megalocornea is present from birth.
A family history of megalocornea may be present.
The mother may have slightly enlarged corneas.
Physical
Findings of simple megalocornea
See the list below:
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Symmetric
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Dome-shaped cornea
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Normal corneal thickness
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Normal endothelial cell density, usually bilateral
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Usually good visual acuity
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With-the-rule astigmatism common
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Corneal diameter usually 13.0-16.5 mm
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Corneal thickness normal and stroma clear; may have central mosaic dystrophy (see the image below)
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Limbus sharply demarcated
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Keratometry usually normal but may be steeper than normal
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Anterior chamber depth increased
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Lens-iris diaphragm positioned posteriorly
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Vitreous length short
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Intraocular pressure normal
Findings of anterior megalophthalmos
See the list below:
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Megalocornea
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Ciliary body band wider than the trabecular meshwork and scleral spur on gonioscopy [2]
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May have any of the following:
Iridodonesis
Iris stromal hypoplasia
Transillumination defects
Phacodonesis
Ectopia lentis
Cataracts
Krukenberg spindles
Posterior embryotoxon
Excessive mesenchymal tissue in the angle
Glaucoma (but not congenital glaucoma)
Findings of congenital glaucoma not found in megalocornea
See the list below:
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Elevated intraocular pressure
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Corneal edema and Haab striae
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Increased axial length
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Decreased endothelial cell density
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Flatter cornea
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Decreased lens thickness
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Asymmetry
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Optic disc cupping
Causes
Megalocornea is inherited as an X-linked recessive trait (90% of cases).
The gene locus for X-linked megalocornea is in band Xq12-q26, most likely band Xq21-q23.
Autosomal dominant, autosomal recessive, and sporadic inheritance have been reported.
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Central mosaic dystrophy sometimes noted in megalocornea.
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Megalocornea.
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Megalocornea patient with Artisan lens.
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B-scan ultrasound showing a large flat iris.
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Aphakic megalocornea patient with 15 mm white to white.
