Diabetic Retinopathy
A progressive complication of diabetes resulting in damage to the retinal blood vessels, potentially leading to vision loss.
Emergency Management: Acute vitreous hemorrhage or macula-off tractional retinal detachment requires urgent ophthalmologic evaluation and possible prompt surgical intervention (vitrectomy).
Diabetic retinopathy is a microvascular complication of both type 1 and type 2 diabetes mellitus characterized by progressive damage to the retinal microvasculature. It primarily affects the retinal capillaries, leading to microaneurysms, vascular leakage, and eventual capillary occlusion. The condition is the leading cause of incident blindness in working-age adults globally.
Detailed Overview
Chronic hyperglycemia induces biochemical abnormalities including the activation of the polyol pathway, increased advanced glycation end-products (AGEs), and protein kinase C activation. These lead to the loss of pericytes and endothelial cell death, causing blood-retinal barrier breakdown and capillary nonperfusion. Progressive retinal ischemia stimulates the overexpression of vascular endothelial growth factor (VEGF). High VEGF levels drive pathological neovascularization, characteristic of the proliferative stage, which can bleed into the vitreous or cause tractional retinal detachment.
Epidemiology & Demographics
Prevalence is approximately 34.6% among all adults with diabetes. The incidence increases with the duration of diabetes; after 20 years, over 60% of type 2 and nearly 99% of type 1 diabetics develop some degree of retinopathy.
Etiological Mechanism
The primary etiology is sustained systemic hyperglycemia. Additional contributing factors include coexisting systemic hypertension and dyslipidemia, which further exacerbate microvascular endothelial damage.
Primary Causes
Type 1 Diabetes Mellitus
Type 2 Diabetes Mellitus
Chronic hyperglycemia leads to the accumulation of sorbitol and AGEs, causing selective apoptosis of retinal intramural pericytes. This weakens capillary walls, forming microaneurysms (the earliest clinical sign). Endothelial dysfunction leads to increased vascular permeability, allowing lipid and fluid leakage into the macula (diabetic macular edema). Subsequent capillary occlusion causes retinal ischemia. Hypoxia-inducible factor-1 (HIF-1) upregulates VEGF and angiopoietin-2, promoting the growth of fragile, abnormal new blood vessels on the retinal surface and optic disc (proliferative diabetic retinopathy).
Diagnostic Criteria & Guidelines
Diagnosis is based on dilated fundus examination revealing characteristic signs (e.g., microaneurysms, hard exudates, neovascularization). Optical Coherence Tomography (OCT) is required to quantify central subfield thickness for DME (e.g., >320 µm in men, >305 µm in women). Fluorescein Angiography shows leakage from microaneurysms, capillary non-perfusion, and hyperfluorescence of neovascularization.
For severe NPDR or PDR: Panretinal photocoagulation (PRP) using an argon laser to ablate ischemic peripheral retina (typically 1200-1500 burns). For Center-Involving DME: Intravitreal anti-VEGF injections (e.g., Aflibercept 2mg every 4 weeks for 5 doses, then every 8 weeks; or Ranibizumab 0.3mg monthly). Systemic control: Optimize HbA1c to <7.0%, blood pressure to <130/80 mmHg.
Second-Line & Adjunctive Therapy
For persistent DME failing anti-VEGF: Intravitreal corticosteroids (e.g., Dexamethasone 0.7 mg intravitreal implant every 4-6 months, or Fluocinolone acetonide 0.19 mg implant). Warning: high risk of cataracts and IOP elevation.
Surgical & Procedural Management
Pars Plana Vitrectomy (PPV). Indications include: non-clearing vitreous hemorrhage (>1-3 months), tractional retinal detachment involving or threatening the macula, and combined tractional/rhegmatogenous retinal detachment.
Patient Counseling & Advice
Emphasize that early stages are asymptomatic and vision loss is often preventable if caught early. Instruct that controlling blood sugar, blood pressure, and cholesterol is as important as eye treatments. Warn against sudden strenuous activities if diagnosed with PDR.
Follow-Up & Monitoring Schedule
Type 1 diabetes: Initial exam 5 years after diagnosis, then annually. Type 2 diabetes: Initial exam at time of diagnosis, then annually. Women with preexisting diabetes who become pregnant should be examined in the 1st trimester and monitored closely throughout pregnancy. Patients with established retinopathy need follow-up every 1-6 months depending on severity.
Preventive Strategies
Primary prevention involves strict glycemic and blood pressure control. The DCCT trial demonstrated that intensive glycemic control reduces the risk of developing retinopathy by 76%.
With timely laser or anti-VEGF therapy, the risk of severe vision loss is reduced by over 90%. However, without treatment, severe PDR has a >50% rate of severe vision loss within 5 years.