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Saving the eyesight of diabetic patients begins at diagnosis
Treatments for diabetic eye disease have been greatly advanced, but some of the most basic lessons are still the most important.
During the course of treatment, endocrinologists will invariably have to send their diabetic patients to an ophthalmologist to be examined for the host of complications stemming from their disease. Chief among these potential problems is diabetic retinopathy. Although non-proliferative retinopathy does not pose a significant threat to a patient’s vision, the bleeding and swelling caused by proliferative retinopathy can have a devastating effect.
The American Diabetes Association estimates that between 12,000 and 24,000 patients go blind annually as a result of their disease. Additionally, 21% of type 2 diabetes patients have retinopathy at the time of disease diagnosis, and almost all patients with type 1 and type 2 diabetes will develop some degree of it after 20 years.
An annual obligation
Despite statistics such as these, patients with diabetes often do not receive their recommended annual dilated eye examination, according to Jay S. Duker, MD, director of the New England Eye Center and chairman of the department of ophthalmology at Tufts University School of Medicine in Boston.
“The number one impediment to treating these problems is not failure of our therapies to halt the disease; it’s that the patients too often come to our office too late.”
Duker added that diabetic patients should receive these annual exams as soon as they are diagnosed. Although it isn’t a standard requirement for juvenile diabetes patients to be examined during their first five years of treatment, getting them to visit the ophthalmologist can help instill a lifelong habit. These measures can reflect positively on the referring physician as well, as many HMOs look to these annual examinations to benchmark a physician’s capabilities.
Although primary physicians and endocrinologists receive training to identify the tell-tale signs of diabetic eye disease, ophthalmologists are needed to identify the subtler indications of declining vision.
“We can see things like lipid exudation in the retina, which are yellow spots, and also cotton-wool spots, which are fluffy whitish retinal areas of ischemia,” said Allen C. Ho, MD, a retina surgeon at Wills Eye Hospital and an associate professor of ophthalmology at Thomas Jefferson University, both in Philadelphia. “The experienced endocrinologist can detect some of these things with a direct ophthalmoscope, but really what these patients need are full dilated eye exams so we can review the entire retina and the entire eye.”
Ho and others in the ophthalmology community actively encourage healthy habits in these patients to address problems before they have a chance to occur.
“We try to follow the guidelines of the Diabetes Complication Control Trial, emphasizing HbA1c less than 7 and tighter blood sugar control to reduce complications including diabetic retinopathy, kidney damage and neuropathy,” Ho said.
Preemptive measures also include asking patients to partake in daily aerobic activity, such as walking or cycling. Water aerobics can be substituted in cases where patients have diabetic foot and leg disease.
If a patient presents with diabetic macular edema (DME), a swelling of the macula that is the number-one cause of vision loss in diabetic retinopathy, the initial focus turns to systemic issues. Problems with blood pressure and blood sugar, unknown fluid retention and renal dysfunction can all exacerbate DME, and need to be monitored and evaluated. A reduction in macular leakage following laser treatments is unlikely unless these factors are reasonably under control.
Progress with lasers
Clinical trials such as the Early Treatment Diabetic Retinopathy Study (ETDRS) have clearly indicated that focal laser treatment reduces the risk of vision loss and decreases retinal thickening. This is usually employed for patients with less-severe nonproliferative retinopathy.
Proliferative retinopathy resulting in neovascularization that in turn causes bleeding and scaring in the eye, and adverse effects including vitreous hemorrhaging and traction retinal detachment, requires diffuse scatter laser photocoagulation. This process induces regression of the abnormal blood vessels growing on the optic nerve, retina and iris, and has greatly improved the chances that vision will not be further impaired.
“It used to be that if patients with diabetes mellitus lived long enough, nine out of 10 would go on to legal blindness,” Ho said. “Laser, along with awareness of diabetes and an expansion of treatment options has certainly shifted the burden of diabetic vision loss significantly. We’re now able to preserve vision in many of our patients.”
Patients with proliferative retinopathy participating in the ETDRS had less than a 5% rate of legal blindness within five years, and only 1% had severe vision loss.
If numbers such as these give hope to those recently diagnosed with diabetes, the outlook is less optimistic for those whose condition has already caused significant damage.
“We’ve treated diabetic retinopathy for more than 30 years with laser, and while it’s effective in preventing further visual loss in most cases, it rarely improves vision in those who have already suffered visual loss.”
Novel treatments
For Duker and others in the ophthalmology community the real hope lies in the assortment of new agents being tested in diabetic eye disease. Injections of intravitreal Kenalog, an anti-inflammatory used to reduce DME, have had positive results both alone in combination with laser treatments.
Also in the pipeline are several anti-vascular endothelial growth factor drugs, which can block the development of new blood cells and potentially prevent the damage caused by neovascularization. Most prominent among these is pegaptanib sodium injection (Macugen, Eyetech Pharmaceuticals), an agent primarily indicated for age-related macular degeneration, but which has also shown considerable promise in the treatment of DME. The FDA has granted fast-track status to pegaptanib sodium injection, and it could be available to physicians as early as next year.
Researchers are also testing whether the progression of diabetic eye disease can be stymied through protein kinase C inhibitors that can be administered orally.
“Certainly our surgical and treatment techniques have improved for our patients with advanced diabetic eye disease in areas such as bleeds, vitreous hemorrhaging, and scarring with traction retinal detachment,” Ho said. “We’re doing a better job, but there’s still a definite opportunity for improvement and a lot of activity looking for new treatments in our field.”
Gains have also been made in the other areas of diabetic eye disease, but the lessons of promoting healthy lifestyles among patients and getting them to their ophthalmologist annually still hold true. As cataracts, glaucoma and corneal disease are all significantly more common in this patient group, the earlier they are caught the less likely they are to inflict permanent damage.
A visit to the ophthalmologist’s office can also catch other potentially damaging, non-diabetes related complications.
“A fairly common problem for these patients is that they can get neuropathy of one of the cranial nerves that moves the eye, and this can cause double vision,” Duker said. “It almost always gets better on its own, but if they complain of double vision it’s important that they see an ophthalmologist to check that it’s not something else, such as an aneurism.”
Common goal
According to Ho, one of the more meaningful advances in the field has nothing to do with treatments, but is instead focused on improving communication between ophthalmologists and other physicians.
“Ophthalmologists have realized that many of our classification schemes of diabetic eye disease are bewildering to non-eye care specialists,” he said. “There’s emphasis on simplifying classification of diabetic eye disease into non-proliferative diabetic retinopathy and proliferative diabetic retinopathy using new criteria to establish mild, moderate, and severe non-proliferative diabetic retinopathy. The bottom line is to try to make things easier for primary care specialists, endocrinologists, and ophthalmologists to speak, and to establish some kind of common terminology and language.”
Taken together, these techniques and treatments give patients with diabetes the best opportunity yet to combat one of the most distressing adverse events of their disease. – by John Watson