DEGENERATIVE MYOPIA

DEGENERATIVE MYOPIA

What is myopia?
Myopia (nearsightedness) is the inability to focus on objects in the far distance, but with the ability to see close objects well. This visual problem is a result of an elongation of the eyeball (see figure 1) so that distant objects cannot be focused on the retina by the lens of the eye. Parallel rays of light entering the eye from the distance are brought to focus in front of the retina, thus creating a blurred image. Spectacles and contact lenses can correct this visual abnormality.

Figure 1. Cross section of a myopic eye.

How common is myopia?
The most common, mild type of myopia has been reported in 25% of the adult population in the United States and in 25% to 35% of school children. High degrees of myopia are called degenerative myopia or pathological myopia and occur in 1% to 9% of adults in different countries.

What is the cause of myopia?
Genetic factors influence the development of myopia. However, the causes of most cases of myopia are poorly understood. Only a few rare forms of myopia have been reproduced experimentally.

How does myopia cause retinal disease?
Because the eyeball is elongated, the tissues within the eye, including the retina, are stretched and are thinner than normal. The stretching makes the retina prone to several disorders:

1) If this stretching occurs at the back wall of the eye, it creates a special type of macular degeneration. Sometimes this “Myopic Macular Degeneration” can be treated with Laser photocoagulation or Photodynamic Therapy. Myopic macular degeneration is usually less severe than Age Related Macular Degeneration.

2) If this stretching occurs at the equator of the eye, it can cause a condition called Lattice Degeneration. Lattice degeneration, in turn, increases the risk of Retinal Tears and Retinal Detachment. The incidence of Retinal tears and detachments is higher in myopic people than in non-myopic people.

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