Diabetic Retinopathy
GENERAL PRINCIPLES
Classification
• DR is classified as preproliferative retinopathy (microaneurysms, retinal infarcts, lipid exudates, cotton wool spots, and/or microhemorrhages) with or without macular edema, and proliferative retinopathy.
• Other ocular abnormalities associated with diabetes include cataract formation, dyskinetic pupils, glaucoma, optic neuropathy, extraocular muscle paresis, floaters, and fluctuating visual acuity. The latter may be related to changes in BG levels.
• The presence of floaters may be indicative of preretinal or vitreous hemorrhage, and immediate referral for ophthalmologic evaluation is warranted.
Epidemiology
The incidence of DR and vision impairment has dropped significantly with improved management of glycemia, blood pressure, and lipids in patients with both T1DM and T2DM. Early identification and treatment of DR have further reduced vision impairment once it is diagnosed. DR is less frequent in T2DM, but maculopathy may be more severe. It is the fifth leading cause of severe vision loss or blindness worldwide.30
DIAGNOSIS
Annual examination by an ophthalmologist is recommended at the time of diagnosis of all T2DM patients and at the beginning of puberty or 3-5 years after diagnosis for patients with T1DM. Dilated eye examination should be repeated annually by an optometrist or ophthalmologist because progressive DR can be completely asymptomatic until sudden loss of vision occurs. Early detection of DR is critical because therapy is more effective before severe maculopathy or proliferation develops. Any patient with diabetes and visual symptoms should be referred for ophthalmologic evaluation.31
TREATMENT
Glycemic control is first-line therapy to prevent DR progression. Blood pressure management, using ACE inhibitors or ARBs, and addition of fenofibrate in individuals with hyperlipidemia can also benefit DR. Preproliferative retinopathy is not usually associated with loss of vision unless macular edema is present (25% of cases). The development of macular edema or proliferative retinopathy (particularly new vessels near the optic disk) requires elective laser photocoagulation therapy or intra-ocular injections of vascular endothelial growth factor (VEGF)-neutralizing antibodies. For macular edema, anti-VEGF therapies have better outcomes than laser therapy to preserve vision, and anti-VEGF therapies are also a reasonable alternative to laser photocoagulation for proliferative retinopathy. Vitrectomy is indicated for patients with vitreous hemorrhage or retinal detachment.