New evidence from a nationwide study shows that treatment for some powerful beams of light can substantially reduce the risk of blindness for some people with severe eye disease caused by diabetes. This finding, announced today by Carl Kupfer, M.D., Director of HEW’s National Eye Institute (NEI), has potential importance for the more than 300,000 Americans whose sight is threatened by diabetic retinopathy, a leading cause of blindness in the U.S.
The evidence comes from cumulative analysis of data collected for more than two years in the NEI-funded Diabetic Retinopathy Study(DRS), the largest multi-center clinical trial in the history of eye research. The DRS is evaluating the safety and effectiveness of two forms of photocoagulation treatment for diabetic retinopathy the green argon laser and the white xenon arc light beams in reducing the risk of severe visual loss from this disease. Over 1,720 patients and 16 U.S. medical centers are participating in the 10-year investigation, supported by NEI contracts totaling over $1 million a year.
Today is the first announcement of results from the DRS. According to physicians and statisticians monitoring the Study, there is now clear evidence that treatment reduces the risk of blindness when diabetic retinopathy has reached a moderately severe stage as defined by specific changes within the eye.*
In particular, the Study to date has shown that photocoagulation reduces by more than half the risk of blindness in eyes with extensive new blood vessels on or near the optic disc, the place where the optic nerve meets the retina. Information obtained in the Study also indicates that treatment can reduce the risk of blindness for eyes that have a hemorrhage in the vitreous fluid and either early new vessels on or near the optic disc, or extensive new vessels away from the optic disc.
Because of uncertainty concerning the value of photocoagulation when the DRS began, only one eye of each Study patient was treated. However, because there is now firm evidence that treatment is effective in reducing the risk of blindness in the above groups of eyes, and that this beneficial effect is not likely to be reversed, DRS investigators are now recommending that photocoagulation be considered for initially untreated eyes in these groups.
It should be noted that after two years of follow-up the great majority of eyes in the Study, whether treated or untreated, did not go blind. But, the percentage which did go blind was significantly greater among untreated eyes (16.3 percent) than among treated eyes(6.4 percent).
A large number of DRS patients have untreated eyes in which retinopathy is less severe and for which treatment is not now being recommended. These eyes will continue to be followed closely. Treatment will be considered for these eyes if they later reach a stage of retinopathy for which current or future evidence indicates that photocoagulation may be beneficial.
For this reason, and in order to allow long-term evaluation of photocoagulation treatment, Matthew D. Davis, M.D., emphasized that continued follow-up of all DRS patients is essential. Dr. Davis is Chairman of the DRS Executive Committee and the Department of Ophthalmology at the University of Wisconsin Medical School in Madison.
Certain drawbacks of photocoagulation have also been found. In some Study patients, moderate impairment of visual acuity (sharpness of vision) and narrowing of the visual field (peripheral vision) occurred in the treated eye.
Follow-up thus far shows that the loss in sharp, central vision has been temporary in some patients but has persisted in others. However, DRS physicians believe that these harmful effects of photocoagulation in eyes with moderately severe retinopathy are outweighed by the reduced risk of blindness afforded by treatment at this stage,
All DRS patients have been informed of these findings and are being reexamined to determine the desirability of photocoagulation treatment for their initially untreated eyes. Patients have been asked to remain in the Study in order that follow-up may continue.
A paper presenting the data and other scientific and ethical considerations underlying today’s announcement will be published in the April 1976 issue of the American Journal of Ophthalmology. An advance copy of this paper has been sent to more than 10,000 practicing ophthalmologists in the U.S. and the nearly 3,000 physicians member of the American Diabetes Association.
As further results are obtained, they will be made known to all DRS patients. They will also be published in medical journals in order that physicians throughout the world can use the information for the benefit of their patients and will be conveyed to the general news media for wide public dissemination.
Diabetic retinopathy, associated with long-standing diabetes, follows a progressive and variable course. In many people with the disease, new abnormal blood vessels form on the surface of the retina, protrude into the vitreous fluid which fills the center of the eye, and bleed. Although the blood may clear from the eye on its own, it often remains, causing severe loss of vision. Scar tissue may also form and then contract, resulting in detachment of the retina and blindness.
Photocoagulation employs finely focused beams of intense light to create a number of minute burns on the retina. The treatment is used to destroy or inhibit the growth of the abnormal retinal blood vessels in hope of preventing bleeding and subsequent visual loss. The photocoagulation light beam must be accurately aimed and therefore cannot be used when severe hemorrhage in the vitreous fluid obscures the areas of the retina to be treated.
When the DRS began in 1971, the risks and benefits of photocoagulation and not been adequately assessed, although this treatment had been in use for more than a decade. It was therefore considered best to limit treatment in the DRS to only one eye. If treatment were found to be beneficial, each patient would have a chance to be helped; if it were found to be harmful, no patients would be exposed to this risk in both eyes.
Only patients with both eyes medically eligible for treatment were enrolled in the DRS, and the eye to be treated was chosen randomly. A random process was also used to choose the type of treatment, either argon laser or xenon arc photocoagulation. Random selection of both the eye to be treated and the type of treatment helped assure that the treated and untreated groups of eyes were comparable and that any differences that might be detected between the two groups could be ascribed to the effects of treatment.
*In the DRS, blindness or “severe vision loss” is considered to have occurred if visual acuity in a given eye is less than 5/200 at two or more consecutively completed four-month follow-up visits.
# # #
- Preliminary Report on The Effects of Photocoagulation Therapy. The Diabetic Retinopathy Study Group. Am J Ophthamol. 1976 Apr. PubMed