Diabetic Eye Disease:
Q: “My doctor says I have diabetes. Why do I need an eye exam?”
A: Diabetes is the leading cause of "preventable" blindness in the US.
Diabetes is a systemic illness that over time can cause damage to multiple organs in the body, including the eye. The two main ocular conditions at risk in diabetics are diabetic retinopathy and cataracts. Certainly cataracts develop as a normal aging process of most patients even without diabetes, but diabetics may develop cataracts at an earlier age and experience more rapid deterioration in vision. If you would like to know more about cataracts and cataract surgery, please refer to the cataract link.
Diabetic retinopathy is a potentially blinding condition caused by damage to blood vessels that nourish the retina, the light-sensitive inner lining of the back of the eye. The normal retina senses patterns of light brought into focus by the cornea and lens, and relays this information through the optic nerve to the brain, where images are perceived. Both type 1 and type 2 diabetics are at risk for diabetic retinopathy.
The development and progression of diabetic retinopathy is directly related to the control of blood glucose. Maintaining your blood hemoglobin A1C level below 7.0 greatly reduces your risk of retinopathy. In other words, strict control of blood glucose may prevent or reduce the development of diabetic retinopathy. In fact, improved control may even cause regression of existing retinopathy. There is also a link between the length of time one has diabetes and the risk of developing retinopathy. The longer a patient has diabetes, the greater the likelihood of retinopathy.
Diabetic retinopathy has two forms: nonproliferative and proliferative. This classification refers to the absence or presence of new growing blood vessels. The disease begins in the nonproliferative form and may progress to the proliferative form. In the early stages of nonproliferative disease tiny balloon-like sacks, called microaneurysms, develop along retinal blood vessels. These may leak fluid causing retinal swelling and blurred vision. As the disease progresses, blood vessels may become blocked off leading to cessation of blood supply to parts of the retina. These portions of retina deprived of blood send chemical signals that order the growth of new blood vessels (proliferative disease). The newly growing blood vessels are abnormal and are prone to leaking fluid or even bleeding into the eye. These vessels grow along the retina and into the vitreous jelly. Scar tissue may accompany the vessels, which may contract and cause a retinal detachment in advanced cases.
Vision loss occurs in one of two ways. Leaking of fluid from microaneurysms into the macula – the part of the retina where your best, straight-ahead vision occurs – may cause blurry or distorted vision. Bleeding into the eye from proliferative disease may limit vision by blurring or actually blocking vision, giving the appearance of a dark obstruction to sight. It is important to note that potentially treatable and serious damage to retinal blood vessels may occur before vision becomes affected.
The treatment of diabetic retinopathy involves first better control of your blood glucose. If retinopathy has reached a stage where vision is affected or threatened your doctor may recommend treatment in the office with either a laser or anti-VEGF injections into the eye. Laser treatment is reserved for patients with distinct leaking of blood vessels not in the center of the macula. Laser is also used for treatment of proliferative retinopathy when abnormal new blood vessels are present in the retina. Newer, and sometimes more successful treatment, now includes the use of serial anti-VEGF drugs injections into the eye. Less commonly, surgery may be required. This may be indicated in instances of bleeding into the eye that does not clear on its own, or when a membrane of blood vessels and scar tissue causes a retinal detachment.