It’s estimated that about 80% of people who have had diabetes for 10 or more years are in danger of developing diabetic retinopathy (DR). Retinopathy is caused by damage to the vessels that carry blood to the retina, the part of the eye that receives light through the lens and transmits light signals to the brain. Usually there are no early warning signs, but if retinopathy gets to an advanced stage people can become blind, which is why experts recommend that those with diabetes have an eye examination at least once a year. If retinopathy is detected early, it can be treated with drug injections or by laser therapy, although surgery might be needed in advanced cases. The most common medications used to treat retinopathy include aflibercept (brand name Eylea), ranibizumab (Lucentis) and bevacizumab (Avastin). Research on diabetic retinopathy is ongoing, and new information is being steadily brought to light. Recently, Medscape Medical News, a leading online medical resource for physicians, published a summary of some of the latest research on diabetic retinopathy.
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Here are some of the retinopathy research findings
For nearly 20 years, the DRCR Retina Network (formerly the Diabetic Retinopathy Clinical Research Network), has been studying the clinical care of diabetic eye disease through a series of protocols. They are named by letters of the alphabet, such as Protocol AA, Protocol AB, Protocols S, T, U and V. Jay Sridhar, MD, of the Bascom Palmer Eye Institute in Miami, used data from the Protocol V trial to reevaluate the need for aggressive treatment in patients with diabetic macular edema (DME), which is a build-up of fluid in the center of the retina that’s caused by diabetic retinopathy. From examining the information, he concluded that patients who have diabetic macular edema but also have fairly good vision might not need aggressive treatment. As he explained, “for patients with good vision — about 20/25 or better — and macular edema, I’m much more likely to observe or bring them back in a couple months for another appointment or imaging and not immediately jump to injection.”
Other retinopathy information came from Protocol T. This initiative compared aflibercept, ranibizumab and bevacizumab, which are called anti-VEGF drugs. VEGF, which stands for vascular endothelial growth factor, is a protein that encourages the growth of new blood vessels. That’s normally a good thing, but an over-production of VEGF can promote retinopathy, as well as age-related macular degeneration, which is why anti-VEGF drugs, administered by injection into the eye, are front-line therapy in preventing blindness related to diabetes. There are basically two kinds of diabetic retinopathy: nonproliferative and proliferative. “Proliferative” refers to the presence of abnormal blood vessel growth; “nonproliferative” is an early stage without the abnormal growth. Protocol T indicated that patients with nonproliferative diabetic retinopathy were more likely to see improvement with aflibercept or ranibizumab than with bevacizumab after one year of treatment, but not after two years. Patients with proliferative retinopathy, however, were more likely to see improvement at two years with aflibercept. Dr. Sridhar concluded, “If I have a patient with DME who doesn’t respond well to my initial therapy — and I usually use bevacizumab first-line — I have a lower threshold after a couple of injections to switch to either ranibizumab or aflibercept because there may be a difference in efficacy.”
Finally, news also came from a report on another trial called PANORAMA. This trial, which included 402 patients, compared aflibercept to sham injection for the improvement of moderately severe to severe nonproliferative diabetic retinopathy without diabetic macular edema. The results found that of the patients who received the fake therapy, 58% developed vision-threatening complications in the first two years of the PANORAMA trial. Aflibercept, however, lowered the risk of developing these complications by 75% in the same time period. According to trial investigator Charles C. Wykoff, MD, “Improvements in diabetic retinopathy severity achieved with aflibercept loading doses were maintained through one year with every 16-week re-treatments, a management approach that could realistically be achieved in the real world.” For his part, Dr. Sridhar said, “One of the things that the study emphasized was that a significant percentage of these patients progressed to worsening diabetic retinopathy proliferative disease. So it’s really important to monitor these patients closely and to have a low threshold for starting either laser treatment of anti-VEGF treatment if you see progression.”