As we examine characteristics of diabetic retinopathy it shows to have very similar pathologies to that of both nephropathy and neuropathy. Its development seems to be slightly more common in Type II than Type I diabetes, especially at or shortly after the time of the actual diabetic diagnosis. Regardless the type of diabetes, the usual percentage of incidents of occurrences of retinopathy will begin gradually then increase dramatically as the years of disease duration approaches twenty.
One of the first signs of changes taking place within the eye is the development of microaneurysms in retinal capillaries. Vision does not seem to be affected at this point so this event will usually go unnoticed by the person involved, but an opthamologist should be able to detect it. Then the next progression of diabetic retinopathy is excessive vascular permeability causing leakage of the retinal capillaries. Now, at this stage at least some impairment of vision becomes more likely to occur.
There is evidence that a period of capillary vascular occlusion takes place shortly before the next development which is the vasoproliferation stage commonly known as proliferative diabetic retinopathy (PDR). PDR is responsible for the more severe types of visual loss associated with this complication. PDR is the growth of new unstable vessels in the retina that have an increased likeliness of bleeding which may lead to fibrosis, retinal detachment and blindness. The first risk factor to examine is hyperglycemia. Hyperglycemia seems to play the most integral role in the progression of this complication which is vascular in nature.
The elevated serum levels of glucose is responsible for the increase in oxidant stress, production of sorbitol and thickening of basement membrane within the lens in the eye. Oxidant stress causes damage through the production of free radicals in ocular tissue and also is associated with retinal detachment. The accumulation of sorbitol, through the polyol pathway, will cause an osmotic imbalance that will lead to impaired cell function within the eye and the possible development of cataracts. The thickening of capillary basement membranes is likely the end result of incurred vascular damage caused by either one or a combination of the oxidant stress and sorbitol accumulation.
Now, that we have covered some of the more plausible causes of diabetic retinopathy, let us look at what can be done to prevent or reverse this condition. As with development of other diabetic complications, the need to correct or improve blood sugar control is the first place to start.
There are a number of studies, especially those from the Diabetes Control and Complication Trial, that confirm good blood glucose control will delay or even prevent diabetic complications.
The next area that should addressed, is that of oxidant stress. It has been well concluded that patients with diabetes suffer from increased oxidant stress as compared to non-diabetics. Also, patients with diabetes have lower serum levels of antioxidants including vitamin C, E and beta carotene.
Oral supplementation of antioxidants have shown be effective in treating the conditions that precipitate retinopathy.[i] [ii] Vitamin E has been proven to normalize retinal blood flow that is usually decreased in patients with diabetes. Another study showed excellent results in the treatment of retinopathy with vitamin B6.[iii] Like other diabetic complications that have elevated sorbitol levels, treatment with inositol shows some benefit. The use of zinc supplementation might offer a protective action to the retina as demonstrated in this study of Type I patients with diabetes.[iv]
There are several herbs that display properties that make them particularly effective in directly treating diabetic retinopathy. One is an extract of the leaf of the bilberry plant. It has the ability to decrease the permeability and tendency to hemorrhage in the capillaries within the eye and may offer some systemic benefit as well.[v] [vi] Ginkgo biloba extract has been well known for its value in treating conditions in the circulatory system. This trial of Ginkgo biloba showed significant improvement in the condition of diabetic retinopathy in its participates.[vii]
Since the development of retinopathy or any complications for that matter are multi-factorial, the most complete approach to treatment should be the utilization of all of the known effective therapies available.
Dr. Brian P. Jakes, Jr., N.D., C.N.C. is a Board Certified Doctor of Naturopathy as well as a Certified Nutritional Consultant. In his practice, in Mandeville, LA, Dr. Jakes works with physicians to treat a large number of diabetes patients.[i] Jacques PF, Taylor A, Hankinson SE, Willett WC. Long term vitamin C supplement use and prevalence of early age related lens opacities. Am J Clin Nutr 1997 Oct;66(4):911-6. [ii] Grattagliano I, Vendemiale G, Boscia F, Micelli-Ferrari T. Oxidative retinal products and ocular damages in diabetic patients. Free Radic Biol Med 1998 Aug;25(3):369-72. [iii] Ellis JM, Folkers K, Minadeo M, VanBuskirk R, Xia LJ, Tamagawa H. A deficiency of vitamin B6 is a plausible molecular basis of the retinopathy of patients with diabetes mellitus. Biochem Biophys Res Commun 1991 Aug 30;179(1):615-9. [iv] Faure P, Benhamou PY, Perard A, Halimi S, Roussel AM. Lipid peroxidation in insulin dependent diabetic patients with early retina degenerative lesions: effects of an oral zinc supplementation. Eur J Clin Nutr 1995 Apr;49(4):282-8. [v] Scharrer A, Ober M. Anthocyanosides in the treatment of retinopathies. Klin Monatsbl Augenheilkd
1981 May;178(5):386-9.[vi] Boniface R, Robert AM. Effect of anthocyanins on human connective tissue metabolism in the human.
Klin Monatsbl Augenheilkd 1996 Dec;209(6):368-72.[vii] Lanthony P, Cosson JP. The course of color vision in early diabetic retinopathy treated with Ginkgo biloba extract. J FR Ophtalmol 1988;11(10):671-4.