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Sachin Kalyani, M.D.
12-01-2010
Trinidad and Tobago Information Author: Ahad Deen, M.D.
- Diabetes can lead to bleeding in the back of the eyes in 75% of diabetics over 10 years.
- Trinidad and Tobago has one of the highest(comparative prevalence 11.7) number of new cases of diabetics with an estimated 107,700 persons affected with diabetes in 2010.
- Extrapolating to the number of new cases of diabetic retinopathy, an estimated 50-75,000 persons may be affected.
- Patients with diabetic retinopathy in Trinidad and Tobago have a high incidence of an aggressive form of retinopathy which demonstrates scar tissue formation without significant bleeding.
- Every person with diabetes should have a dilated eye exam once they are diagnosed.
- Over 50% of diabetics in Trinidad and Tobago have never had a dilated fundus examination.
- Presently dilated eye examinations are done at ophthalmology clinics in the general hospitals and by private ophthalmologists.
- Laser treatment done when indicated can prevent significant loss of vision; but if given too late, cannot stop loss of vision.
- For cases that are unresponsive to or too late for laser therapy, early surgical intervention is available by private vitreoretinal surgeons and referrals from the ophthalmology clinics in general hospitals.
- Thus the key to preserving vision is properly timed laser therapy when vision is still good, as determined by an ophthalmologist.
- Retinal vascular complications of diabetes mellitus are classified into nonproliferative and proliferative forms.
- Non-Proliferative Diabetic Retinopathy (NPDR) describes the earliest retinal changes of diabetic retinopathy, resulting from damage to the small blood vessels in the retina.
- Proliferative Diabetic Retinopathy (PDR) describes a later stage of retinopathy, with new growth of abnormal blood vessels on the surface of the retina.
- Leading cause of blindness in US population, 20 - 64 years of age
- There are 5,000 new cases of legal blindness each year secondary to diabetic retinopathy.
- Duration of diabetes and severity of hyperglycemia is directly associated with an increased prevalence of diabetic retinopathy in people with both type 1 and type 2 diabetes.
- After 20 years of diabetes, nearly 99% of patients with type 1 and 60% with type 2 have some degree of diabetic retinopathy.
- Frequency of diabetic retinopathy is higher among non-Hispanic blacks (27%) and Mexican Americans (33%) than in non-Hispanic whites (18%) over 40 years of age.
- NPDR: microaneurysms, dot-and-blot intraretinal hemorrhages, hard exudates, retinal edema, venous beading, intraretinal microvascular abnormalities (IRMA), cotton wool spots (nerve fiber layer infarcts), areas of capillary nonperfusion
- In PDR, new blood vessels, which are fragile and can easily bleed, form on the retina or iris
- Some patients will never develop NPDR or PDR.
- Dilated fundoscopic examination is the best way to diagnose diabetic retinopathy
- In areas underserved by ophthalmologists, retinal photographs can also be used to make the diagnosis.
- Symptoms: Frequently asymptomatic; may cause decreased or fluctuating vision (which may also be due to refraction errors induced by hyperglycemia or hypoglycemia); floaters; difficulty with night vision; shadows or areas of vision missing
- Mild NPDR is defined as microaneurysms only
- Moderate NPDR is defined as more than microaneurysms (i.e. microhemorrhages, hard exudates or cotton wool spots), but less than the definition for severe NPDR
- NPDR 4:2:1 rule -- severe NPDR defined by presence of any 1 of the following, and very severe NPDR by 2 of the following: 1) Diffuse intraretinal hemorrhages and microaneurysms in 4 quadrants; 2) Venous beading in 2 quadrants; or 3) Intra retinal microvascular abnormalities (IRMA) in 1 quadrant
- Severity of NPDR is significant in that laser photocoagulation may be indicated for more severe stages.
- PDR: Signs of NPDR in addition to neovascularization of the disc (NVD) or elsewhere in the retina (NVE), preretinal hemorrhage, vitreous hemorrhage, fibrovascular proliferation on posterior vitreous surface, tractional retinal detachment
- Principal goal is prevention of diabetic retinopathy by good glycemic control.
- The Diabetes Control and Complications Trial (DCCT): intensive glycemic control reduced the risk of new retinopathy by 76%, and slowed progression by 54%, in type I diabetes
- The United Kingdom Prospective Diabetes Study (UKPDS): intensive control of blood glucose reduced the risk of microvascular complications by 25%, mostly due to the decreased need for retinal photocoagulation, in patients with type 2 diabetes. Also from UKPDS: intensive blood pressure control reduced microvascular complications by 37%, reduced progression of retinopathy by 34%, and reduced moderate vision loss by 47%.
- Hypertension, carotid artery occlusive disease, advanced diabetic renal disease and anemia may have an adverse effect on diabetic retinopathy.
- Pregnancy is associated with a transient but reversible worsening of retinopathy.
- The FIELDS study: treatment with fenofibrate in type 2 diabetes reduces the need for laser treatment for DR, independent of changes in plasma lipids.
- The ACCORD Eye Study Group (Chew) recently reported that among participants with type 2 diabetes at high risk for cardiovascular disease, participants who had intensive versus standard glycemic treatment (<6% versus 7-7.9%) had 33% lower rate of retinopathy progression and those who had fenofibrate and simvastatin versus simvastatin alone also had 40% lower rates of retinopathy progression. No significant effect was seen with intensive blood pressure control.
- Early Treatment Diabetic Retinopathy Study (EDTRS): aspirin has neither a beneficial nor harmful effect.
- Although antivascular endothelial growth factors are used in the treatment of severe NPDR and PDR, currently evidence is insufficient to recommend its routine use.
- Intravitreal injections of steroids may be considered in eyes with persistent loss of vision when conventional treatment has failed.
- The mainstay of treatment for severe NPDR and PDR is thermal laser photocoagulation in a panretinal pattern to induce regression
- The Diabetic Retinopathy Study (DRS) showed a 50% or greater reduction in severe visual loss with PDR or severe NPDR treated with panretinal photocoagulation (PRP) over 5 years
- Vitreous hemorrhage and tractional retinal detachment (both complications of PDR) may be treated surgically by vitrectomy
- The goal of vitrectomy is to relieve vitreoretinal traction and to facilitate retinal reattachment.
- Diabetic Retinopathy Vitrectomy Study (DRVS): early vitrectomy was beneficial in type I diabetes with severe vitreous hemorrhage; however, there was no advantage in type 2 diabetes
- Current recommendation: if PRP has not been performed, early surgical intervention is recommended for a severe vitreous hemorrhage due to PDR.
- Vitrectomy is indicated when progression of a tractional retinal detachment threatens the macula
- Type 1 diabetes:examine 5 years after onset of diabetes mellitus, then annually if no retinopathy is seen
- Type 2 diabetes: examine at diagnosis, then annually if no retinopathy is seen
- During diabetic pregnancy: examine before pregnancy, each trimester, and 3-6 months postpartum
- The key to successful management of DR is to make the diagnosis early and treat appropriately to prevent development of further ophthalmic complications.
- Cataract surgery can worsen or cause progression of diabetic retinopathy
- Diabetic retinopathy, including macular edema, should be treated prior to performing cataract surgery (if severity of cataract does not hinder view of the retina)
- Important: Significant DR can be entirely without symptoms.
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