Which is the most common early feature of diabetic retinopathy: September 2011
Ans. A: Dot and blot hemorrhages Ophthalmoscopically, the earliest change of background diabetic retinopathy characteristically affects the smaller blood vessels. Small dot and blot haemorrhages are common Diabetic retinopathy It is retinopathy (damage to the retina) caused by complications of diabetes mellitus, which can eventually lead to blindness. It is an ocular manifestation of systemic disease which affects up to 80% of all patients who have had diabetes for 10 years or more. Signs and symptoms Diabetic retinopathy often has no early warning signs. As new blood vessels form at the back of the eye as a pa of proliferative diabetic retinopathy (PDR), they can bleed (ocular hemorrhage) and blur vision. In most cases, it will leave just a few specks of blood, or spots, floating in a person's visual field, though the spots often go away after a few hours. On funduscopic exam, one see cotton wool spots, flame hemorrhages (similar lesions are also caused by the alpha-toxin of Clostridium novyi), and dot-blot hemorrhages. Elevation of blood-glucose levels can also cause edema (swelling) of the crystalline lens (hyperphacosorbitomyopicosis) as a result of sorbitol (sugar alcohol) accumulating in the lens. This edema often causes temporary myopia (nearsightedness). A common sign of hyperphacosorbitomyopicosis is blurring of distance vision while near vision remains adequate. Pathogenesis Diabetic retinopathy is the result of microvascular retinal changes. Hyperglycemia-induced intramural pericyte death and thickening of the basement membrane lead to incompetence of the vascular walls. These damages change the formation of the blood-retinal barrier and also make the retinal blood vessels become more permeable. During the initial stage, called nonproliferative diabetic retinopathy (NPDR), most people do not notice any change in their vision. Early changes that are reversible and do not threaten central vision are sometimes termed simplex retinopathy or background retinopathy. Some people develop macular edema. It occurs when the damaged blood vessels leak fluid and lipids onto the macula. The fluid makes the macula swell, which blurs vision. Proliferative diabetic retinopathy (PDR) (or PDRP) As the disease progresses, severe nonproliferative diabetic retinopathy enters an advanced, or proliferative, stage when blood vessels proliferate (i.e. grow). The lack of oxygen in the retina causes fragile, new, blood vessels to grow along the retina and in the clear, gel-like vitreous humour that fills the inside of the eye. Without timely treatment, these new blood vessels can bleed, cloud vision, and destroy the retina. Fibrovascular proliferation can also cause tractional retinal detachment. The new blood vessels can also grow into the angle of the anterior chamber of the eye and cause neovascular glaucoma. Nonproliferative diabetic retinopathy shows up as cotton wool spots, or microvascular abnormalities or as superficial retinal hemorrhages. Risk factors All people with diabetes mellitus are at risk - those with Type I diabetes (juvenile onset) and those with Type II diabetes (adult onset). The longer a person has diabetes, the higher the risk of developing some ocular problem. People with Down's syndrome, who have three copies of chromosome 21, almost never acquire diabetic retinopathy. This protection appears to be due to the elevated levels of endostatin, an anti-angiogenic protein, derived from collagen XVIII. The collagen XVIII gene is located on chromosome 21. Management There are three major treatments for diabetic retinopathy, which are very effective in reducing vision loss from this disease. These three treatments are laser surgery, injection of triamcinolone into the eye, and vitrectomy. Although these treatments are very successful (in slowing or stopping fuher vision loss), they do not cure diabetic retinopathy. Laser photocoagulation It is widely used for early stages of proliferative retinopathy. Panretinal photocoagulation Panretinal photocoagulation, or PRP (also called scatter laser treatment), is used to treat proliferative diabetic retinopathy (PDR). The goal is to create 1,600 - 2,000 burns in the retina with the hope of reducing the retina's oxygen demand, and hence the possibility of ischemia. Intravitreal triamcinolone acetonide Triamcinolone is a long acting steroid preparation. When injected in the vitreous cavity, it decreases the macular edema (thickening of the retina at the macula) caused due to diabetic maculopathy, and results in an increase in visual acuity. The effect of triamcinolone is transient, lasting up to three months, which necessitates repeated injections for maintaining the beneficial effect. Complications of intravitreal injection of triamcinolone include cataract, steroid-induced glaucoma and endophthalmitis. Vitrectomy Instead of laser surgery, some people require a vitrectomy to restore vision. A vitrectomy is performed when there is a lot of blood in the vitreous. It involves removing the cloudy vitreous and replacing it with a saline solution.
Dot and blot hemorrhages
Oedema
Hard exudates
Neovascularization