Diabetic Retinopathy

Abstract

The North American leading cause of blindness in people between 25 and 75 years of age is Diabetic Retinopathy. Just like Diabetes Mellitus the early stages of the disease are asymptomatic and progress slowly toward an irreversible acquired blindness. Hg A1c and fasting glucose are efficient screening tools to identify patient at risk of developing Diabetic retinopathy. In addition, fundospocy is another efficient method to detect early microaneurysms and to adjust the therapeutic plan.
Most often patients will complain of floaters in their visual field. Annual follow up and patient education are among the most efficient approaches to prevent and limit the damage of Diabetic Retinopathy.

by Christian Haddad
 

Full Article

Diabetes is known to be a disease that affects multiple organs in the human body.  As a matter of fact, diabetes causes many lesions to the eyes.  However, lesions to the retina are the worst.  This process of retinal damage is known as diabetic retinopathy.

Type I Diabetes

Patients with type 1 diabetes mellitus usually have a higher prevalence of diabetic retinopathy than patients with type 2 diabetes mellitus. However, since patients with type 2 Diabetes mellitus usually are diagnosed after they become symptomatic, hence many years after the onset of the actual diabetic damaging process, many patients have significant retinal lesions at the time of diagnosis.

Upper picture is seen by a healthy patient. Lower picture is seen by a patient suffering from diabetic retinopathy.

Prevention

To prevent diabetic retinopathy and to slow down the procession of the disease, a very intensive control of blood glucose has to be accomplished. In fact, this type of control will also prevent other complications of diabetes in other organs like the kidney, heart, limbs, and brain. Hence, glycosylated hemoglobin has to be closely monitored.

The progression of diabetic retinopathy has been classified in two stages:  nonproliferative diabetic retinopathy and proliferative diabetic retinopathy.  The names of these two stages are descriptive of the lesions seen by the ophthalmologist examining the eye. Therefore, initially diabetic retinopathy starts with a nonproliferative phase which consists of leaking and occluded capillaries. On examination, the ophthalmologist will see macular edema, dot-and-blot hemorrhages, hard exudates and microaneurysms. When macular edema becomes clinically significant the patient will experience some mild to moderate visual loss.   

The patient suffering from non proliferative diabetic retinopathy can progress to a more severe form where vessels in the retina become tortuous and a widespread picture of abnormalities in the smallest vessels of the retinas. At this stage, 40% of affected patients will develop the most severe form of diabetic retinopathy within a year. Even with very close control some patients progress to the stage that all ophthalmologists work on preventing: proliferative diabetic retinopathy.

Responsible for sever visual loss in diabetic retinopathy; proliferative diabetic retinopathy is neovascularization that happens in response to ischemia caused by the previously occluded vessels in the nonproliferative stage. If this vessel formation process happens on the iris it will lead to severe glaucoma. However, usually this process takes place on the retina itself. These newly formed fragile vessels on the retina are prone to bleeding into the vitreous of the eye and may cause traction retinal detachment. If such a complication occurs, laser surgery with vitrectomy will be performed hoping to save the remaining vision and restore some of the lost vision.

Annual Follow-ups

Since many patients will be asymptomatic at very advanced stages of diabetic retinopathy an annual follow up with an ophthalmologist should be routinely performed. At the ophthalmology clinic, the patient should expect to be examined with a slit lamp with various combinations of lenses and to have their pupils dilated as the usual direct ophthalmoscope used in the emergencies rooms is not sufficient to provide satisfactory examination results.  In addition some patients might require more advanced ophthalmologic tests such as fulorescein angiography.

Laser surgery can be used to control leaking blood vessels in patients with macular edema and more extensive laser burning can be used to treat proliferative retinopathy.  The rationale behind the latter treatment is to reduce the metabolic demand of the retina so there will be no need to form new vessels. Very often, one session is not enough and multiple sessions are required to overcome the progressing disease. If the timing is optimal, laser surgery prevents 50 to 90% of severe visual loss.  Finally, women with diabetes should seek a baseline ophthalmic examination before conception, then in the first trimester of pregnancy and every 3 months until childbirth as pregnancy can precipitate diabetic retinopathy.

More reading source: National Eye Institute: Facts About Diabetic Retinopathy

 

Progression of diabetic retinopathy from a schematic point of view:

 

Progression of diabetic retinopathy