Macular dystrophy
 

Diffuse corneal clouding in macular dystrophy Corneal graft in macular dystrophy. Note the  diffuse clouding in the recipient cornea.

There are multiple greyish white opacities involving the stroma and the corneal periphery (in granular and lattice  dystrophy, the periphery is typically spared). The stroma between the opacities is diffusely cloudy. Other possible signs: One or both eyes may have corneal grafts (unlike other stroma dystrophy, the recipient cornea usually  show changes of macular dystrophy because the dystrophy extends to the periphery).

Questions:

1. What is the pathogenesis of macular dystrophy?

Answer
It is a autosomal recessive condition characterised by an accumulation 
of glycoaminoglycan both intra and extracellularly. It is thought to be 
caused by defective sulfotransferase. It is thought to be a type of localized mucopolysaccharidosis.

2. What is mucopolysaccharidoses?

Answer
It is an inborn error of metabolism characterised by glycoaminoglycan
accummulation. The conditoin is usually autosomal recessive except
for Hunter's Syndrome which is X-linked. Most of these patients have
ocular involvement which include corneal cloudiness, retinal pigmentary degeneration and optic atrophy.

3. What is the visual prognosis of patients with macular dystrophy?

Answer
Most patients develop significant visual impairment by the age of 30 
and corneal graft is usually necessary to improve vision. Recurrence
has been reported in grafted cornea and regraft is sometimes necessary.

4. The following is the histology of a patient with macular dystrophy. What stain has been used?

Answer
Macular dystrophy is best shown with alcian blue
and cholloidal iron. In this case, the stain used is
colloidal iron.
 

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