Diabetes and the Eye

How does diabetes affect the eye? Diabetes is a leading cause of vision loss.  Over time diabetes damages the blood vessels in the eye and can cause a variety of problems.  Elevated blood sugars damage a type of cell called the pericyte that supports small blood vessels in the eye.  With loss of these cells, the blood vessels become leaky.  Fluid then leaks out, damaging the surrounding tissues.  These small vessels can also become occluded, cutting off blood supply to the eye.

The retina is the thin layer covering the inside of the eye.  It is the most important part of the eye that allows you to see, similar to the film in a camera.  When blood vessels are damaged in the retina, several problems can occur.  With fluid leakage, the retina can swell and cause blurred vision.  If this persists, the retina can be permanently damaged.

With occlusion of the blood vessels, the retina lacks sufficient blood flow.  This can directly cause permanent loss of vision.  In addition, the remaining retina releases a chemical message telling the blood vessels it does not have sufficient supply.  The blood vessels respond to this, but unfortunately do so in a harmful way.  They start growing new, abnormal blood vessels; this process is called neovascularization.  These vessels are not effective in bringing blood supply back to the retina, and they can cause two significant problems.  First they are fragile, and can easily bleed.  This is called a vitreous hemorrhage, and fills the eye with blood.  Second, the neovascular blood vessels can also contract over time, and pull on the retina.  This can cause a retinal detachment, a very serious, potentially blinding complication.

How is diabetic retinopathy, or damage to the retina, treated? The most important treatment is careful control of the diabetes itself.  Good blood sugar control, blood pressure management, and monitoring of cholesterol are essential to improving diabetic retinopathy.  Without these, other treatments are ineffective.

For the leaking blood vessels, laser surgery is usually indicated.  This is called focal or grid laser.  This can help seal off leaking capillaries, and can also stimulate the retina to absorb the leaked fluid.  Neovascularization is treated with a laser as well, but in a different manner, called panretinal photocoagulation or PRP.  PRP is used to destroy the already permanently damaged portion of the retina that does not have blood flow and is stimulating the blood vessels to grow.  After treatment, the abnormal blood vessels will shrink and disappear.  The retina that is treated is not used in normal vision, and the laser does not typically reduce vision.  Several large studies have shown that this is one of the most effective treatments for preventing blindness in all of ophthalmology.  Both laser therapies are safe and done in the office.  Focal laser is painless.  PRP can be uncomfortable, and so your doctor may give you numbing treatments beforehand.

How often should a diabetic have an eye exam? Diabetics should be examined at least once a year and more frequently with more advanced retinopathy.

While diabetes certainly has the potential to cause blindness, careful blood sugar control and regular monitoring by your ophthalmologist can prevent the great majority of vision loss.