Corneal dystrophies are a group of rare disorders which usually affect the corneas in both eyes. The cornea is the transparent front of the globe of the eye. It owes its transparency to the presence of a regular lattice structure of collagen fibres. Anything which affects this regularity results in loss of the transparency which is essential for good corneal function and health.
This group of disorders tends to run in families and the causes of most corneal dystrophies will lie in individual genetic make-up. They may be present at birth, but more frequently develop during adolescence and progress gradually throughout life. Some forms are mild, others severe.
Although age of onset, symptoms and progression differ in the various dystrophies, most cases of corneal dystrophy fall into three types, classified by their inheritance pattern and appearance.
- Granular Dystrophy usually starts at around 5 years of age. This can be seen as small white dots in the centre of the cornea or may take the form of lines radiating from the centre. These signs can increase in size and number and by 50 years of age, opacities are visible to the naked eye.
- Macular Dystrophy (not to be confused with macular degeneration which affects the retina at the back of the eye) usually starts in the first decade of life and appears as a thin superficial corneal veil with isolated opacities when seen with a slit lamp. It is the least common type of dystrophy. Acute, short lived, attacks may be experienced and there is increasing haziness of the central part of the cornea and increasing isolated opacities.
- Lattice Dystrophy can develop in infancy but more usually during the second decade of life. This is seen as a cobweb of fine lines which develop into a lattice-like pattern. By 40 years of age onwards, the centre of the cornea can become irregular with ill-defined opacity. Although in some people the pattern of progress is less severe, acute attacks are experienced which can contribute to relatively early onset of sight loss.
Among the many other types, Map/Dot/Fingerprint Dystrophy, Fuch’s Dystrophy, Meesman Dystrophy and RET-Buckler Dystrophy are most encountered.
The Genetics of Dystrophies
Dominant, single gene diseases result from one of a pair of matched autosomal genes having a disease and the other being normal. With each pregnancy there is a 1 in 2 chance of the disease appearing in the offspring. Recessive single gene disease requires both parents to carry the condition and this results in a 1 in 4 inheritance risk in each pregnancy. Only siblings within a single generation are affected, unless members of that generation create offspring with another carrier of the specific gene.
It is valuable to seek genetic advice on all conditions, which have an hereditary cause in order to identify how this may affect individual family members.
Although there are many more forms of corneal dystrophy, likely outcome varies with the type of dystrophy. In some conditions corneal grafting offers a good prospect of visual improvement, but there is nothing that can be done to stop a dystrophy that has been diagnosed. If you or someone in your family has been diagnosed with a corneal dystrophy, contact us to make an appointment to discuss your condition.
At cameronoptometry, our examinations involve a thorough examination of all parts of the eye including a high magnification examination of the cornea and all its layers to detect even the earliest signs of corneal dystrophy.
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