Hypertensive Retinopathy

Hypertensive retinopathy is the pattern of retinal vascular damage produced by sustained or acute elevation of blood pressure. It reflects hypertensive end organ injury elsewhere. Mild retinal signs appear in 2 to 15% of nonhypertensive controlled adults over 40, and moderate or severe signs in 2 to 3%.

Descriptive grades:

• Grade 1: mild generalized arteriolar narrowing
• Grade 2: arteriovenous nipping and focal narrowing (moderate)
• Grade 3: flame hemorrhages, cotton wool spots, hard exudates (moderate to severe)
• Grade 4: optic disc swelling with macular star (malignant)

Mechanism: autoregulatory vasoconstriction, then intimal thickening and hyalinization (silver and copper wiring), then breakdown of the inner blood retinal barrier with fibrinoid necrosis and ischemia in acute severe hypertension. Causes of malignant retinopathy include essential hypertension, renal parenchymal disease, pheochromocytoma, renal artery stenosis, preeclampsia and eclampsia, cocaine, and drug withdrawal. Signs predict stroke, coronary events, heart failure and kidney disease. Untreated malignant hypertension has a high one year mortality.

• Chronic disease is usually asymptomatic.
• Acute disease: headache, blurred vision, scotomata, nausea, confusion, seizures.
• Fundus signs: copper or silver wiring, arteriovenous nipping, flame hemorrhages, cotton wool spots, hard exudates in a macular star, retinal edema, optic disc swelling.
• Associated complications: retinal vein or artery occlusion, retinal macroaneurysm, ischemic optic neuropathy.

Red flags: disc swelling, blood pressure above 180/120 mmHg with symptoms (headache, chest pain, dyspnea, neurological signs), young age, pregnancy.

• Blood pressure on both arms, repeated, with ambulatory or home monitoring for chronic disease.
• Dilated fundus examination with photographs.
• Target organ assessment: urinalysis and albumin creatinine ratio, creatinine and eGFR, electrolytes, ECG, echocardiography. Troponin and chest imaging if symptomatic.
• Secondary causes in young or severe disease: renin and aldosterone, plasma metanephrines, renal artery imaging, drug and cocaine screen, pregnancy test.
• OCT and fluorescein angiography only when the cause is unclear or to quantify edema and nonperfusion.

Differentials: diabetic retinopathy, retinal vein occlusion, radiation retinopathy, anemia and leukemic retinopathy, HIV retinopathy, retinal vasculitis, papilledema from raised intracranial pressure.

Chronic hypertension (target below 130/80 mmHg):

• Ramipril 2.5 mg daily, increasing to 10 mg (monitor creatinine and potassium; contraindicated in pregnancy and bilateral renal artery stenosis).
• Amlodipine 5 to 10 mg daily.
• Indapamide 1.5 mg modified release daily (monitor sodium and potassium).
• Salt intake below 5 g/day, weight loss, 150 minutes of aerobic exercise weekly, alcohol limit.

Malignant hypertension and hypertensive emergency:

• Reduce mean arterial pressure by no more than 20 to 25% in the first hour, to about 160/100 mmHg over 2 to 6 hours, then toward normal over 24 to 48 hours. Rapid drops risk optic nerve and cerebral ischemia.
• Labetalol IV 20 mg over 2 minutes, then 40 to 80 mg every 10 minutes to a maximum of 300 mg, or infusion at 0.5 to 2 mg/min. Contraindications: asthma, heart block, bradycardia, acute heart failure.
• Nicardipine infusion starting at 5 mg/h, increased by 2.5 mg/h every 5 to 15 minutes to a maximum of 15 mg/h.
• Treat precipitating causes and monitor in a high dependency setting.

Pregnancy: labetalol 100 to 400 mg orally every 8 to 12 hours, nifedipine modified release 10 to 20 mg twice daily (up to 40 mg twice daily), methyldopa 250 to 500 mg three times daily (maximum 3 g/day). Avoid ACE inhibitors and angiotensin receptor blockers.

Elderly: start doses lower and avoid orthostatic hypotension.

Retinal signs usually resolve over weeks to months with control. Refer to ophthalmology for disc swelling, macular edema or vascular occlusion, with anti-VEGF as needed. Follow up blood pressure every 2 to 4 weeks until controlled, then 6 monthly, with retinal review annually. Counsel on adherence and cardiovascular risk.