Sunday, November 13, 2011

Hypertensive Retinopathy

Signs and Symptoms
The patient with hypertensive retinopathy, as expected, suffers from hypertension. However, the hypertension may be unknown to th e patient and the eye exam may yield the first clue to this relative asymptomatic systemic disease. Most commonly, the patient is middle age or older. In addition, hypertension is more common in African-Americans than Caucasians. Patients with only hypertensive retinopathy are nearly always visually asymptomatic.

Findings in hypertensive retinopathy include cotton wool spots and flame shaped hemorrhages. Only rarely will there be retinal or macular edema. In advanced cases, there will be a macular star (ring of exudates from the disc to the macula) and disc edema. Arteriolosclerosis (arteriolar narrowing, arterio-venous crossing changes with venous constriction and banking, arteriolar color changes, vessel sclerosis) is often found concurrently.

The findings in hypertensive retinopathy all stem from hypertension-induced changes to the retinal microvasculature. Hypertension leads to a laying down of cholesterol into the tunica intima of medium and large arteries. This leads to an overall reduction in the lumen size of these vessels. In arteriolosclerosis, hypertension leads to focal closure of the retinal microvasculature. This gives rise to microinfarcts (cotton wool spots) and superficial hemorrhages. In extreme cases, disc edema develops. The mechanism behind this phenomenon is poorly understood, but it may be related to a hypertension-related increase in intracranial pressure, and hence is considered true papilledema.

Arteriolosclerotic changes in the retinal microvasculature persist even with the reduction of systemic blood pressure. However, hypertensive retinopathy changes resolve over time with the reduction of systemic blood pressure (BP). Cotton wool spots develop in 24 to 48 hours with the elevation of BP, and resolve in two to 10 weeks with the lowering of BP. A macular star develops within several weeks of the development of elevated BP and resolves within months to years after the BP is reduced. Papilledema develops within days to weeks of increased BP and resolves within weeks to months following BP lowering.

Management of hypertensive retinopathy involves appropriate treatment of the underlying hypertension. Medical co-management with the primary physician is of paramount importance. However, if a patient presents with papilledema from hypertension, then the patient has malignant hypertension and should be considered to be in medical crisis. This patient needs immediate consult with a primary care physician and, most likely, immediate transport to a hospital emergency room.

It must be reiterated, however, that there are many causes of papilledema. Other causes of papilledema, such as an intracranial mass lesion, must also be considered in the patient with hypertension. However, in a case where blood pressure is extremely elevated (e.g. 250/150mmHg) and there is disc edema with a macular star, malignant hypertension is the likely cause.

Clinical Pearls

In order for cotton wool spots to develop from hypertension, autoregulatory mechanisms must first be overcome. For this to happen, the patient must have at least 110mmHg diastolic readings.

Patients who develop papilledema from hypertension have malignant hypertension and typically have BP in the range of 250/150mmHg

Fluorescein angiography is not indicated in cases of hypertensive retinopathy as it yields no diagnostic information.

Hypertensive retinopathy presents with a ‘dry’ retina (few hemorrhages, rare edema, rare exudate, and multiple cotton wool spots) whereas diabetic retinopathy, in comparison, presents with a ‘wet’ retina (multiple hemorrhage, multiple exudate, extensive edema, and few cotton wool spots).

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