Q&A: Diabetic Retinopathy
Disclaimer: The responses provided through this service are not intended to replace consultation with an ophthalmologist. This question and answer service is intended for general educational purposes only and the responses represent the approach of the responding physician given the facts presented, not necessarily the only or best method or procedure in every case.
QUESTION: My husband contracted diabetic retinopathy after he was treated by radiation therapy for nasopharyngeal cancer. Is this a common occurrence? How long will damage from this radiation continue to cause damage to his eyes? Is there anything we can do to help him regain his eyesight?
ANSWER: Probably what your husband has developed is radiation retinopathy. Though radiation retinopathy has some similarities to diabetic retinopathy, there are differences as well.
Both involve loss of normal retinal blood vessels with subsequent growth of abnormal blood vessels that can easily bleed, as well as leakiness of the residual normal blood vessels. The cause is different.
In radiation retinopathy, the cells that make up the retinal blood vessels are damaged by the radiation so they can not multiply and therefore they slowly die off. In diabetic retinopathy, the blood vessels close off because of small blood clots.
For diabetic retinopathy, a much more common problem, a large study sponsored by the National Institute of Health involving many ophthalmologists throughout the country showed the efficacy of avoiding diabetic retinopathy by controlling blood sugars. They also showed that if the abnormal blood vessels developed, laser treatments to the retina would markedly decrease the chances of bleeding. Finally, laser would also stop the normal blood vessels from leaking. No such study exists for radiation retinopathy. In certain situations, because of the similarities some of us would consider laser treatment of the retina for this condition.
As to how common it is, as you know, nasopharyngeal cancer is an uncommon disease that used to be very fatal. With radiation, many patients are now surviving the disease. Some will develop radiation retinopathy if the area radiated involved the eye. Damage tends to be progressive. Consideration to laser treatment can be given in certain situations though they may not be successful as in diabetic retinopathy. Also hyperbaric oxygen treatments may be helpful and should be considered. Again, no large study has definitely shown the worth of either of these treatment modalities.
QUESTION: I have a friend who has lost a lot of her sight from a retina disease she has been told is “Harada’s disease.” Is this what diabetic retinopathy refers to? If it isn’t, where can I get information about it? Any help would be appreciated since I have looked all over for information and have been unable to find any. We have been very frustrated by this lack of information. Many thanks.
ANSWER: Harada’s disease is not related to diabetic retinopathy. Harada’s disease is a disease where the body reacts against certain organs of the body. This is called an autoimmune disorder.
What causes the body to react against itself is unknown. We know that there may be a genetic predisposition. Asians and people with Native American ancestry are more at risk. This does not mean that even if you have the gene you will get this problem, it just means that if you have a certain gene and something else happens (what this second thing is we are not sure) then you may develop Harada’s disease.
Harada’s disease can cause inflammation in the eye and swelling of the retina. Harada’s can also affect the hearing and this can be undiagnosed. A hearing test is indicated because up to 80% of patients with Harada’s may have hearing problems. They can also have headaches and some loss of skin coloration.
Treatment is usually with steroids and the patients usually do well with this treatment. Many patients actually develop a long remission following treatment. Treatment should be performed by someone specialized in the treatment of uveitis or retinal conditions.
QUESTION: Can you tell me if the damage done from diabetic retinopathy can be healed or reconstructed so the vision loss is not permanent?
ANSWER: It is important to know that the results of the Diabetes Control and Complications Trial (DCCT) study showed that good control of blood sugars decreased the development of diabetic retinopathy by 75% in patients with no diabetic retinopathy at the start of the study. If diabetic retinopathy was present at the start of the study, there was a decrease in the rate of progression by 50% compared to those who did not control their blood sugars well.
Once diabetic retinopathy occurs, if it progresses to a certain point, then laser treatment decreases the chances of visual loss. Finally, if severe visual loss occurs, sometimes vitrectomy (a surgical procedure) can restore vision in some cases.
Overall, if patients are followed carefully, blindness can be avoided in 90% of patients with diabetic retinopathy.
QUESTION: Is diabetic retinopathy treatable with thalidomide?
ANSWER: This is a very interesting question. Thalidomide prevents growth of new vessels. It is the new vessels in the eye that cause marked visual loss in diabetic retinopathy.
The problem is that new vessel growth elsewhere in the body is actually helpful. For instance, inhibiting blood vessel growth in the heart would be severely detrimental. So giving thalidomide by mouth may decrease new vessel growth in the eye (actually, this has not been shown yet), but it could also cause loss of blood vessel growth in the heart, muscles or brain, which would be very bad.
Therefore, since no study has shown that this would be helpful therapy, the best therapy is still good sugar control (which has been shown to be helpful in decreasing progression of diabetic retinopathy) or laser treatments if the diabetic retinopathy has gotten to a certain stage.
Reference: D’Amato, R. J., Loughan, M. S., Flynn, E. & Folkman, J. (1994). Thalidomide is an inhibitor of angiogenesis. Investigative Ophthalmology & Visual Science, 35, 4 supp., 1996.
QUESTION: I am interested in learning more about diabetic retinopathy. Could you tell me how many Americans each year are diagnosed with diabetic retinopathy? Also, how many laser surgeries for this disease are performed each year and if possible what percentage of these surgeries result in full restoration of one’s vision. Are there any breakthroughs in diagnosis or treatment that I should know about?
ANSWER: There are an estimated 65,000 new cases of proliferative diabetic retinopathy and 75,000 new cases of diabetic macular edema each year. In addition, there are 8,000 new cases of blindness caused by complications of diabetes reported yearly.
I don’t have statistics on how many laser surgeries are performed. However, studies have shown that timely laser surgery can reduce the risk of visual loss from proliferative diabetic retinopathy by 90%, and can reduce the risk of moderate visual loss from diabetic macular edema by 50%.
The most important recent study has been the DCCT which showed that compared to patients with poor sugar control, in patients without diabetic retinopathy, tight control decreased the rate of progression by 75%. If diabetic retinopathy was present tight control decreased the rate of progression by 50%. Once diabetic retinopathy reached certain thresholds, then laser treatment can decrease the progression of visual loss as well . There are ongoing studies into the causes of development of abnormal blood vessels in the eye in diabetes as well as what causes the loss of normal blood vessels in diabetes.
