Diabetic retinopathy (DR) is a chronic microvascular complication of diabetes mellitus and one of the leading causes of preventable blindness worldwide. Persistent hyperglycaemia damages the retinal blood vessels, resulting in retinal ischemia, increased vascular permeability, haemorrhage, exudation, and pathological neovascularization. Poor glycaemic control, hypertension, diabetic nephropathy, pregnancy, and long duration of diabetes accelerate disease progression. Early detection through regular retinal screening together with optimal control of blood glucose, blood pressure and lipids can prevent visual loss and reduce the risk of blindness.

Risk Factors

• Long duration of diabetes mellitus

• Poor glycaemic control

• Hypertension

• Diabetic nephropathy

• Pregnancy

• Dyslipidaemia

• Smoking

• Obesity

• Increasing age

Clinical Presentation

Early diabetic retinopathy is frequently asymptomatic.

Patients may present with:

• Blurred vision

• Progressive reduction in visual acuity

• Floaters

• Distorted vision

• Difficulty reading

• Sudden visual loss due to vitreous haemorrhage or retinal detachment

Diagnostic Criteria

Diagnosis is established by retinal examination after pupillary dilatation demonstrating characteristic diabetic retinal lesions.

Investigations

Screening Recommendations

Annual diabetic retinopathy screening is recommended for all people with diabetes.

Screening should begin:

• Women planning pregnancy: comprehensive eye examination before conception and during the first trimester (preferably at booking). Further follow-up depends on the degree of retinopathy.

• Type 1 diabetes diagnosed after puberty: begin screening five years after diagnosis.

• Type 1 diabetes diagnosed before puberty: begin screening at puberty.

• Type 2 diabetes: begin screening at the time of diagnosis.

Comprehensive Ophthalmic Assessment

Each screening visit should include:

• Visual acuity assessment without and with spectacles

• Pinhole visual acuity if visual acuity is less than 6/9

• Pupillary dilatation using a mydriatic agent (e.g., tropicamide)

• Assessment for cataract or other media opacities

• Retinal examination using direct or indirect ophthalmoscopy or fundus photography

• Identification and grading of diabetic retinopathy and diabetic maculopathy

• Documentation of findings and scheduling of the next screening visit

Grading of Diabetic Retinopathy and Recommended Follow-up

Key: R = Retinopathy, M = Maculopathy, P = Photocoagulation, U = Unclassifiable.

Management

Non-Pharmacological Management

• Perform yearly diabetic retinopathy screening for all people with diabetes.

• Ensure comprehensive ophthalmic examination according to the recommended screening schedule.

• Maintain optimal glycaemic control to slow disease progression.

• Intensify blood pressure control.

• Manage dyslipidaemia appropriately.

• Encourage smoking cessation.

• Educate patients about the importance of regular eye examinations even when vision is normal.

• Refer patients with sight-threatening diabetic retinopathy or diabetic maculopathy promptly to an Eye Clinic.

• Laser photocoagulation should be performed where indicated to prevent visual loss.

Prevention

• Achieve and maintain good glycaemic control.

• Control hypertension aggressively.

• Treat dyslipidaemia.

• Stop smoking.

• Attend annual retinal screening.

• Ensure timely referral and treatment of sight-threatening retinopathy.

• Women with diabetes should undergo eye assessment before pregnancy and during pregnancy according to the recommended schedule.

Prognosis

The prognosis of diabetic retinopathy depends largely on the stage of disease at diagnosis and the adequacy of glycaemic, blood pressure, and lipid control. Patients with no or mild non-proliferative diabetic retinopathy generally have an excellent prognosis when regular annual screening and optimal metabolic control are maintained. Moderate disease requires closer follow-up because of the increased risk of progression. Severe non-proliferative and proliferative diabetic retinopathy are associated with a high risk of irreversible visual impairment and blindness if left untreated; however, timely referral, laser photocoagulation, and appropriate ophthalmic management can substantially reduce the risk of severe vision loss. Pregnancy, diabetic nephropathy, uncontrolled hypertension, poor glycaemic control, and long duration of diabetes are associated with faster disease progression and a poorer visual prognosis.