The cornea is the clear ‘window’ into the eye. It has three layers:
1. Epithelium – a thin skin on the outside surface
2. Stroma – the middle layer, made of tough connective tissue
3. Endothelium – a very thin layer of cells on the inside surface
The stroma has a natural tendency to absorb water, which would disrupt the precise arrangement of collagen fibres and make it cloudy: the cells of the endothelium work constantly to pump water out of the stroma, keeping it dehydrated and clear.
However, these cells die as we go through life, and the eye is unable to make new ones: eventually there may not be enough endothelial cells to keep the cornea clear. This is referred to as ‘corneal decompensation’.
Typically, the first symptom of decompensation is poor vision first thing in the morning, with the sight gradually returning to normal over an hour or two. This is due to the cornea becoming waterlogged when the eyes are closed overnight: once the eyes are open, a small amount of water is lost by evaporation, which results in the cornea slowly clearing.
What is Fuchs’ dystrophy?
Fuchs’ dystrophy (Ernst Fuchs, 1851-1930) is a slowly-progressive inherited condition which affects the endothelium. It is very variable between individuals; but may finally result in the symptoms described above. It can be made worse by eye operations such as cataract surgery, although it is usually possible for the examining doctor to detect it before surgery.
How is it treated?
In the early stages, when the vision is blurred for an hour or two in the morning, many patients find they can cope with Fuchs’ without treatment.
Saline eyedrops may be helpful in drawing water out of the cornea, and blowing a hairdryer on the face can increase the drying effect of evaporation, both of which may help to clear the vision.
If the condition progresses and the vision remains hazy for most of the day it may be necessary to perform a corneal transplant – either a penetrating keratoplasty or, more commonly, a DSEK – to replace the endothelium (see separate pages).