I saw two patients (RJ and JR) yesterday that have the same “problem.” They both are patients with diabetes and both have advanced, or proliferative, diabetic retinopathy. Both have had diabetes for over 20 years, are on insulin and have been treated with pan-retinal photocoagulation to control the proliferative diabetic retinopathy. Both still have 20/20 vision. Neither have ever required retinal surgery and probably never will. Their visual prognosis is excellent.
This is not uncommon. My point in writing about them is that there are many, many patients with diabetic retinopathy, even the potentially blinding stage, that see well, even normally. I have taken care of them for several years and they have been stable since receiving pan-retinal photocoagulation (PRP). Future visits with me are limited to looking for signs of recurrence. PRP is not a cure, but it has been the mainstay of treatment since the 1970’s.
What is Pan-Retinal Photocoagulation? Also known as PRP, panretinal photocoagulation is a procedure whereby the “peripheral” retina, or side-retina, is treated with multiple laser burns. The burns are tiny. Usually 1200-1500 burns are necessary for a successful treatment. It does not directly effect vision.
How does Pan-Retinal Photocoagulation Work? The proliferative phase of diabetic retinopathy is notable for the presence of abnormal blood vessels growing on the surface of the retina or iris. These abnormal vessels, called neovascularization, develop as a result of retinal ischemia. Ischemia develops when blood supply is compromised to a tissue and inadequate oxygen supply is delivered to the tissues. In the eye, this results in the production of VEGF (Vascular Endothelial Growth Factor) which basically acts as a fertilizer for the neovascularization. By ablating enough of the peripheral retina, VEGF production ceases, and the neovascularization goes away. Patients are now stable.
Ischemia ——–> VEGF ——–> Neovascularization
Does this Decrease Vision? This does not change your central vision. The PRP treats the so-called “peripheral” retina which may, but usually does NOT, change your peripheral vision. Sometimes, there may be some decrease in going from light to dark situations and vice versa, for example, walking out of a movie theater in the afternoon. Basically, we treat the peripheral retina, to save the central vision – the most important “vision.”
Central Vision is Preserved. In general, when epeople speak of “vision,” we actually are speaking of central vision. Central vision is provided by the macula, the tiny 2mm X 2mm functional center of the retina. It gives us our 20/20 vision, our ability to “stare” at something and gives us the best color and reading vision.
Proliferative diabetic retinopathy does not occur in every diabetic. When caught early, as in the cases above, a life-time of excellent vision can be expected.
Randall V. Wong, M.D.
Ophthalmologist, Retina Specialist