Diabetic retinopathy is the most common diabetic eye disease and a leading cause of blindness in American adults. It is caused by changes in the blood vessels of the retina, the light-sensitive tissue at the back of the eye. In some people, blood vessels may swell and leak fluid. In other people, abnormal new blood vessels grow on the surface of the retina. Over time, diabetic retinopathy can get worse and cause vision loss.
Complications of diabetes may affect the eye tissue when blood sugar and blood pressure are not kept under control. Elevated blood sugar damages the fine capillary blood vessels that deliver oxygen and nutrients to the retina, the nerve layer at the back of the eye that senses light and sends images to the brain. This damage is called diabetic retinopathy.
There are two types of diabetic retinopathy:
- Nonproliferative diabetic retinopathy (NPDR)
- Proliferative diabetic retinopathy (PDR)
Nonproliferative diabetic retinopathy (NPDR) is the early stage of retinopathy where tiny blood vessels within the retina leak blood or fluid causing it to swell or form deposits called exudates. Mild NPDR often has no affect to vision. When vision is affected, however, it is the result of damage to the macula, a small area in the center of the retina. This retinal area allows for clear vision of very fine details.
There are two types of macular conditions:
- Macular edema: a swelling or thickening of the macula. The swelling is caused by fluid leaking from retinal blood vessels called micro anuerisms. It is the most common cause of visual loss in diabetes. Vision loss may be mild to severe, but peripheral vision usually continues to function.
- Macular ischemia: the closing of small blood vessels. Vision blurs because the macula no longer receives sufficient blood supply to function properly.
Proliferative diabetic retinopathy (PDR) is when abnormal new blood vessels begin to grow on the surface of the retina or optic nerve. The new vessel growth is called neovascularization. When there is widespread closure of retinal blood vessels preventing adequate blood flow, the retina responds by growing new blood vessels in an attempt to supply more blood to the area where the original vessels closed.
PDR causes visual loss in the following ways:
- Vitreous hemorrhage: occurs when the fragile new vessels tend to bleed into the vitreous, a clear, gel-like substance that fills the center of the eye. It can a cause a few dark floaters or a very large one blocking all vision. The blood must be reabsorbed in the eye or removed before vision is restored.
- Traction retinal detachment: results as scar tissue from new vessel growth can shrink or wrinkle pulling the retina from its normal position causing visual distortion. Severe vision loss results from detaching large areas of the retina or macula.
- Neovascular glaucoma: is extensive retinal vessel closure causing new, abnormal blood vessels to grow in the iris and in the drainage channels in the front of the eye. It blocks the flow of fluid causing pressure in the eye to build up and damages the optic nerve.
Dr. Robinson may prescribe treatment for diabetic retinopathy with injections of medication, steroids or laser surgery. In advanced cases, a microsurgical procedure (vitrectomy) is performed to replace the blood filled vitreous with a clear solution. The best treatment is early prevention of the condition by controlling blood sugar and blood pressure.