Diabetic retinopathy is a leading cause of blindness in adults. Elevated blood sugar levels are believed to damage the blood vessels in the retina, leading to leakage of fluid into the retina, blockage of capillaries causing ischemia, and growth of new abnormal blood vessels.
Patients with both type I or type II diabetes are at risk of vision loss and require routine retinal evaluations. While many people with diabetes may often not notice changes in their vision early on, diabetic retinopathy usually progresses to cause vision loss which can be severe and permanent.
In NPDR, the small blood vessels in the retina become damaged resulting in microaneurysms, retinal hemorrhages, and accumulation of exudates from leakage of fluid into the retinal tissue. This often results in diabetic macular oedema (DME), which is swelling of the retina in the area that serves central vision. Symptoms of DME include blurry vision which can be severe and may become chronic.
Furthermore as NPDR progresses, the central capillaries that nourish the macula can become blocked, resulting in macular ischemia. Similarly, other non-central retinal blood vessels often become blocked as well. Such retinal deprivation of its normal blood supply results in a cascade of signals that leads to formation of new abnormal blood vessels, leading to the more severe form of diabetic retinopathy.
At this advanced stage, the signals sent by the retina for nourishment trigger the growth of new abnormal blood vessels (neovascularization) which grow along the surface of the retina. The fragility of these new unhealthy blood vessels can cause them to bleed, which can lead to severe vision loss and even blindness. Further proliferation and subsequent scar formation can then follow, leading to complicated cases of tractional retinal detachment.
Another complication of PDR is neovascular glaucoma where the outflow path for fluid that is constantly being produced in the eye is obstructed by the new abnormal blood vessels. This leads to dangerously high eye pressures which can also result in permanent and severe vision loss. Diabetic macular edema (DME), which can cause severe blurry vision, may occur at any stage, either non-proliferative or proliferative of diabetic retinopathy.
Optimizing blood sugar levels as well as controlling cholesterol and blood pressure can slow the development and progression of diabetic retinopathy. However, in many cases, additional ocular treatments become necessary.
Anti-angiogenic intravitreal injections, which stop abnormal blood vessel growth and leakage, have become the mainstay in controlling diabetic macular edema (DME) and are an important adjunct in treating complications of retinal neovascularization in PDR. Once the retinal disease stabilizes, less frequent injections will be necessary.
Laser treatment is used to augment and prolong the effect of such injections. The goal of using focal or grid laser treatments to treat DME is to stabilize vision by attempting to stop damaged blood vessels from leaking fluid into the retina. For PDR complicated by vitreous hemorrhages, retinal detachment, or neovascular glaucoma, laser treatment cannot be replaced by anti-angiogenic injections, but is rarely provided alone.
PDR and sometimes severe NPDR are treated with panretinal laser photocoagulation (PRP). During this laser procedure, the peripheral retina, which is not receiving adequate blood flow, is treated in order to stop the development of abnormal blood vessels. Such laser treatment stops the formation of new abnormal blood vessels and in most cases causes existing ones to shrink. PRP can prevent the blinding complications of diabetic retinopathy in the majority of cases.
In addition, intraocular steroid injections have become a standard treatment option for diabetic patients with macular edema who do not respond well to anti-angiogenic injections or laser treatment alone or in combination. During such treatment, a small amount of steroid is injected into the eye using a tiny needle or specialized injection device. Steroid injections are associated with particular side effects, mainly elevated eye pressure and cataracts. These can generally be managed with simple treatments but more aggressive therapy may be needed in some cases.
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