Hypertension and the Eye

Systemic hypertension damages the retinal, choroidal and optic nerve circulations (target organ damage), and the retina is the only place where small vessels can be directly observed. It is also a cause of retinal vascular occlusion, glaucoma risk, and optic neuropathy.

• Ocular manifestations:
  • Hypertensive retinopathy: chronic effects of sustained elevated pressure (arteriolar narrowing and arteriovenous nipping) and acute severe elevation (haemorrhages, exudates, disc swelling).
  • Hypertensive choroidopathy: Elschnig spots (focal retinal pigment epithelial infarcts), Siegrist streaks, and serous retinal detachment, in acute severe hypertension, pre-eclampsia, and renal disease.
  • Hypertensive optic neuropathy: optic disc swelling in malignant (accelerated) hypertension.
  • Associated disorders: retinal vein occlusion, retinal artery occlusion, retinal arterial macroaneurysm, ischaemic optic neuropathy, ocular motor palsies, and diabetic retinopathy progression.
• Causes of severe hypertension: essential hypertension, renal disease, renovascular disease, primary aldosteronism, phaeochromocytoma, pre-eclampsia and eclampsia, Cushing syndrome, and drugs (cocaine, amphetamines, NSAIDs, ciclosporin, oral contraceptives).

• Often asymptomatic; severe disease causes blurred vision, headache, field defects, transient visual loss, or sudden visual loss.
• Retinal signs by severity:
  • Mild: generalised or focal arteriolar narrowing, widened light reflex (copper wiring), and arteriovenous nipping.
  • Moderate: flame haemorrhages, dot haemorrhages, cotton wool spots, hard exudates (macular star), and microaneurysms.
  • Malignant: bilateral optic disc swelling with severe retinopathy (haemorrhages, exudates and cotton wool spots), serous retinal detachment, and choroidal infarcts; blood pressure usually above 180/120 mmHg with encephalopathy, renal failure, and cardiac strain.
• Retinal vein occlusion: dilated tortuous veins, widespread haemorrhages. Artery occlusion: sudden painless visual loss with pale retina and cherry red spot.
• Retinal arterial macroaneurysm: focal arteriolar dilatation with haemorrhage and exudate in the elderly hypertensive woman.

• Blood pressure measurement in both arms and, when needed, ambulatory monitoring.
• Visual acuity, pupils, dilated fundus examination, retinal photography, optical coherence tomography (macular oedema, subretinal fluid, choroidal changes), and fluorescein angiography for ischaemia, leakage, and choroidal non-perfusion.
• Systemic evaluation: renal function, urinalysis (protein), electrolytes, lipids, glucose, ECG and echocardiogram, plasma renin and aldosterone, urinary or plasma metanephrines, and pregnancy testing; imaging for renal artery stenosis where suspected.
• Exclude other causes of disc swelling (raised intracranial pressure) with neuroimaging when the clinical picture is atypical.

• Treat the hypertension as the primary therapy; the eye findings reflect the systemic emergency.
• Hypertensive emergency (malignant hypertension with retinopathy or encephalopathy): admit to a monitored unit; lower mean arterial pressure by no more than 20 to 25 percent in the first hour, then to about 160/100 mmHg over 2 to 6 hours, then to normal over 24 to 48 hours, to avoid hypoperfusion of the brain, eye (ischaemic optic neuropathy), and kidneys. Intravenous options: labetalol 20 mg bolus then 20 to 80 mg every 10 minutes (maximum 300 mg) or infusion 0.5 to 2 mg/min; nicardipine 5 mg/hour increased by 2.5 mg/hour every 15 minutes to a maximum of 15 mg/hour; sodium nitroprusside 0.25 to 0.5 micrograms/kg/min short term. In pre-eclampsia: labetalol or nifedipine and magnesium sulphate 4 g IV then 1 g/hour, with delivery planning. Phaeochromocytoma: alpha blockade (phentolamine 5 mg IV, phenoxybenzamine 10 mg twice daily) before beta blockade.
• Chronic hypertension: target below 130/80 mmHg using ACE inhibitor or angiotensin receptor blocker, calcium channel blocker (amlodipine 5 to 10 mg daily), and thiazide like diuretic (indapamide 1.5 mg daily); lifestyle (salt restriction, weight loss, exercise, reduced alcohol, smoking cessation).
• Retinal complications: retinal vein occlusion with macular oedema: intravitreal anti-VEGF (ranibizumab 0.5 mg or aflibercept 2 mg monthly) or dexamethasone implant; neovascularisation: panretinal photocoagulation; retinal artery occlusion: emergency stroke assessment and cardiovascular workup; macroaneurysm: observation, laser or anti-VEGF, vitrectomy for submacular haemorrhage.
• Follow up: retinal findings resolve over weeks to months with blood pressure control; permanent optic atrophy or macular damage can remain.
• Screening: annual dilated fundus examination in those with diabetes and hypertension; retinal grading informs cardiovascular risk (stroke, renal and cardiac events).