Inheritance:
(1) autosomal dominant: CNA1
(2) autosomal recessive: CNA2
Chromosome: 12q21
Gene: KERA
Gene product: keratocan (a leucine-rich proteoglycan)
Clinical features:
(1) reduced corneal curvature, usually bilateral
(2) indistinct border at the corneal limbus
(3) arcus lipoides occurring at an early age
(4) poor visual acuity if uncorrected, often with ametropic amblyopia
The recessive form has a centrally-located round and opaque corneal thickening. This is absent in the dominant form.
A patient with congenita plana may have:
(1) sclerocornea
(2) malformations of the iris
(3) slit-like pupil
(4) adhesions between the iris and cornea (Peters' anomaly)
A properly fit contact lens often can provide a good visual and cosmetic outcome.
