Myopic Retinal Degeneration
By Robert L. Epstein, MD
Having nearsightedness means being “sighted” for near objects. Without glasses, the nearsighted person can see objects up close but not objects very far away. The eye is sometimes compared to a camera. Using the camera analogy, in nearsightedness, the focus of light falls short of that camera film of the eye called the retina. A person’s eye may be nearsighted because the eye is too long, because the front wall of the eye is too highly curved, because the internal eye lens bends light too strongly, or some combination of these three causes.
The retina is not actually film at all but a complex, delicate region of nerves and sensors that rests against the white sclera in back of the eye. A few people have eyes that are extremely nearsighted due to an extremely elongated eyeball. These people have a genetic weakness of the white scleral wall of the eye especially that part of the sclera that covers the back of the eye. Certain of these people will unfortunately lose their sight in a condition called myopic retinal degeneration. The delicate retina receives poor support in these cases. For these people the sclera thins and stretches throughout life and little cracks develop in the retina. Blind spots may develop. LASIK laser vision correction for nearsightedness does not cure this condition.
For people starting to have myopic retinal degeneration, the fact that glasses must become increasingly thick is a symptom of a medical problem. Note that the overwhelming majority of people have normal eyes, do not have myopic retinal degeneration, and the need for a stronger eyeglass prescription is not cause for alarm. On the other hand, for the people with myopic retinal degeneration, the delicate sensory retina becomes stretched, may develop breaks and vision begins to permanently blur. The condition was thought to be incurable until recently.
When should you suspect that there is myopic retinal degeneration? Merely needing to change to a more strongly nearsighted eyeglass or contact lens prescription is normal before age thirty and should not be worrisome. Nearly all people with myopic retinal degeneration have a eyeglass prescription stronger than a -8 or contact lens prescription stronger than -7.
In a medical eye exam to detect myopic retinal degeneration, the eye-MD can observe the presence retinal stretching. A very important test for the patient with possible myopic retinal degeneration is an ultrasound exam to find the front-to-back length of the eyeball, the so-called “axial length” measurement. A length longer than 28 mm is highly abnormal.
Medical advances have produced procedures to arrest the degeneration and prevent blindness. There are advances in laser treatments that can be helpful to limit retinal damage when those little retinal cracks occur. Most importantly, a procedure called scleral reinforcement can preserve vision by stopping the stretching of the eye wall.
Epstein is Director of The Center for Corrective Eye Surgery in McHenry.