Inheritance Pattern
AR
Visual Acuity
The primary symptom typically observed in MCD is reduced visual acuity. The extent of visual impairment can vary significantly depending on the location of the corneal opacities. One MCD study reported an average visual acuity of 20/250 to 20/400 Snellen equivalent.
CORNEA
There are multiple gray-white opacities involving the stroma and sparing the corneal periphery.
The stroma between the opacities is diffusely cloudy.
Assess the corneal curvature, astigmatism, and thickness.
Fellow EYE:
Check the fellow eye for similar changes or corneal grafts.
Questions:
What is the pathogenesis of macular dystrophy?
There are two types of macular dystrophy:
• Type I. The most prevalent type. An error occurs in the synthesis of keratan sulfate, as well as in the activity of certain sulfotransferases responsible for sulfating its lactose immunoglycan side chain.
• Type II. Patients with this form synthesize a normal ratio of keratan sulfate and dermatan sulfate-proteoglycans, but synthesis is 30% below normal. In addition, the dermatan sulfate-proteoglycans chains are 40% shorter than normal
How do you define and Classify Corneal Dystrophies?
Corneal dystrophy refers to a bilateral non-inflammatory opacity of the cornea, the transparent outer layer covering the front of the eye. These dystrophies can be categorized based on their location within the cornea and their underlying causes, which are as follows:
Anterior corneal dystrophies affect the corneal epithelium and subepithelium.
Transforming growth factor beta–induced (TGFBI) dystrophies affect the epithelium and stroma.
Stromal corneal dystrophies affect the stroma (the central layer of the cornea).
Posterior corneal dystrophies involve the Descemet membrane and endothelium.
While macular corneal dystrophy is presently categorized as stromal corneal dystrophy, granular and lattice corneal dystrophies are now classified as epithelial-stromal TGFBI dystrophies due to their impact on various layers of the cornea.
What is the usual age of onset of corneal dystrophies?
Most corneal dystrophies typically manifest before the age of 20, with exceptions such as map-dot-fingerprint dystrophy and Fuchs corneal dystrophy
What are the inheritance patterns of corneal dystrophies?
The majority of corneal dystrophies follow an autosomal-dominant inheritance pattern. However, exceptions to this include macular corneal dystrophy and congenital hereditary endothelial dystrophy (CHED), which are inherited in an autosomal-recessive manner. Previously, congenital hereditary endothelial dystrophy was categorized into autosomal recessive CHED2, distinct from autosomal dominant CHED1, which has been removed from classification due to its resemblance to posterior polymorphous corneal dystrophy.
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