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Ophthalmologists at forefront of monitoring, treating diabetes
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Diabetes affects 382 million people worldwide, fully 3.3% of the population. The number of diabetics is expected to double in the next 20 years.
Type 1 diabetes is caused by a failure to produce adequate insulin. It represents about 10% of patients and usually has a younger age of onset and more severe course. Type 2 diabetes is caused by insulin resistance. It represents 90% of patients and is in most cases secondary to lifestyle choices that are increasingly prevalent in advanced countries, including a poor diet, obesity, smoking and lack of physical exercise.
Hypertension is a common associated diagnosis, and both type 2 diabetes and hypertension can respond to behavior modification. Once patients begin to develop diabetic eye disease, the ophthalmologist has a good opportunity to discuss appropriate lifestyle changes with the patient, and many type 2 patients who modify their behavior can essentially cure their disease. A small number of cases occur during pregnancy or as a toxic effect from chemicals or drugs.
Prolonged hyperglycemia causes vascular endothelial pericyte death, and thickening of the basement membrane is seen histologically. This results in incompetence of vascular walls and increased permeability of the blood vessels, breaking down the so-called blood-aqueous barrier.
Ten years after the onset of diabetes, 80% of patients demonstrate at least mild background diabetic retinopathy and 20% manifest diabetic macular edema. Vigilant control of blood sugar levels can delay the onset of these sight-threatening complications, according to the Diabetes Control and Complications Trial and United Kingdom Prospective Diabetes Study, and patients should be educated regarding this fact. It is possible that pancreatic transplantation and insulin pumps will help more diabetics maintain tighter control of their blood sugar in the future.
Every diabetic patient should have a dilated fundus examination every year to monitor for early disease and allow for timely treatment. This is a Healthcare Effectiveness Data and Information Set outcome that is monitored by large health plans, and while some do well, nationwide data suggest that the majority of diabetics do not get an annual dilated fundus examination; even when it is done, communication between the eye doctor and primary care physician is poor. We can and must do better in this area, and our performance in the future will affect our compensation. This is an area in which electronic health records will likely help.
DME is the major cause of central visual acuity loss in patients with diabetes and today is most easily diagnosed with optical coherence tomography. Treatment is indicated, and alternatives, in addition to appropriate panretinal photocoagulation for the usually associated background diabetic retinopathy, include the options of modified macular grid laser using a C-shaped pattern to avoid the fovea, intravitreal steroids and/or intravitreal anti-VEGF injections.
Our retinal colleagues, through a series of well-designed prospective randomized trials, are shedding a great deal of light on the best treatment for DME. These trials include the classic ETDRS and others, including the RIDE, RISE, RESTORE, DRCR.net Protocol I and Protocol T, DA VINCI, VIVID, VISTA and BOLT study, to name a few. For the interested reader, all these trials can be reviewed, and it must be noted that their outcomes are often interpreted differently by every retina specialist.
Most of us rely on a retina specialist to help select and deliver appropriate therapy, but more comprehensive ophthalmologists are treating DME every year as the disease burden and demand for therapy increase. Doing my best to interpret these studies, there remains a role for modified grid photocoagulation, especially when the majority of the edema is perimacular. Intravitreal anti-VEGF appears to be superior to intravitreal steroid for most patients. Monthly injections are required initially, but by year 3 of treatment in the responsive patient, injections may only be required two to four times a year. There is no good evidence that one form of anti-VEGF is superior to another, and the decision among bevacizumab, ranibizumab, and aflibercept is multifactorial and best made in consultation with the patient.
The “triple aim” goals of the Affordable Care Act include reducing cost and will likely drive us toward more use of the lower-cost alternatives if they can be safely compounded.
Patients unresponsive to anti-VEGF therapy may respond to intravitreal or, in select cases, subconjunctival steroids, and some clinicians believe topical NSAID and/or steroid therapy can be helpful, especially in the pseudophakic diabetic patient with macular edema. Secondary cataract in the phakic eye and steroid-induced glaucoma in all eyes is extremely common with long-term and especially intravitreal steroid injections and deserves prompt diagnosis and treatment.
The ophthalmologist’s role in monitoring and treating the patient with diabetes is critical. Patients should be counseled regarding beneficial lifestyle modification, encouraged to pursue tight glucose control, and treated promptly and appropriately when diabetic retinopathy or macular edema occur. Anti-VEGF therapy is moving to the forefront of treatment for DME, but photocoagulation, steroids and NSAIDs retain a useful role.