Hypertension or increased blood pressure is a common yet serious problem affecting millions of people worldwide. Both acute and chronic hypertensive changes occur in the eyes.
The acute changes manifest due to malignant hypertension while the chronic changes from systemic, long-term hypertension.
Introduction to Vascular Damage
The retina of the eye acts as a window to the crucial circulatory system. Blood vessels present in the retina mimic coronary (of the heart) and cerebral (of the brain) microcirculation. Doctors can easily examine and inspect retinal blood vessels. With such examination, early signs of high blood pressure, diabetes, and other diseases can be detected.
Due to high blood pressure, the walls of the retinal blood vessels thicken. It causes the lumen of the blood vessels to become narrow and restrict the blood flow reaching the retina. Over a period of time, hypertension can limit the functioning of the retina by damaging the blood vessels and by putting excessive pressure on the optic nerve. Eventually, it causes vision problems. Thus, retinal vascular damage due to high blood pressure causes a condition known as ‘Hypertensive retinopathy’.
Links to hypertension and cardiovascular complications
Acute hypertension leads to reversible vasoconstriction in the blood vessels of retina while hypertensive crisis can cause optic disc edema. Prolonged elevated blood pressure causes several vascular changes. Thus, hypertension is linked as a risk factor for retinal disorders including hypertensive retinopathy.
Also, raised blood pressure is associated with stroke, other cardiovascular complications and damage to systemic target organs. Signs and symptoms of hypertensive retinopathy are linked with congestive heart failure and coronary heart disease. Its signs are associated with ischemic changes.
Indicator of target organ damage
Poorly controlled blood pressure affects many vital systems of the body including the renal, cardiovascular and the retina. Any damage to these important systems is called ‘target-organ damage’. When hypertension affects retina of the eye, hypertensive retinopathy occurs.
Hypertension does not impair vision. However, hypertensive retinopathy may cause blockage of arteries or veins supplying blood to the retina. This may result in blindness. Hypertensive retinopathy patients are at greater risk of developing hypertensive damage to several other end organs. Thus, it is one of the key indicators of such target organ damage.
About the silent killer that is growing
Hypertensive retinopathy is basically a retinal vascular damage which is caused by elevated blood pressure. This makes hypertension the ‘silent killer’ as the clinical signs of organ damage appear very late in the disease. Hence, it becomes important to refine risk stratification approach to ensure detection of hypertension-related hypertensive retinopathy or end organ damage before the signs cause symptoms.
Symptoms to look for
The signs and symptoms of hypertensive retinopathy do not develop until late in this disease. Generally, it includes visual field defects or blurred vision. Funduscopic examination in the early stages can identify vascular wall changes such as arteriolar constriction, changes in arterio-venous crossings etc.
If the hypertension is chronic or poorly controlled, it can cause:
- Permanent narrowing of arteries
- Arteriovenous nicking
- Arteriosclerosis
In some cases, total vascular occlusion occurs.
If the acute disease becomes severe, then it can lead to the development of:
- Superficial flame-shaped hemorrhages
- Cotton-wool spots
- Yellow hard exudates
- Optic disc edema
Causes and Stages of Hypertensive Retinopathy:
The main cause of Hypertensive Retinopathy is prolonged hypertension. Chronic prolonged raised blood pressure forces the blood against the arteries and veins. When the blood moves at a higher pressure, the force is directly transferred to the blood vessels. This causes a compensatory response and the arteries or veins constrict. However, prolonged hypertension affects the arterial wall tissue and begins to stretch it. Eventually, this high pressure of blood damages the muscle layer, tissue, and endothelium of the blood vessel walls, which causes many complications including hypertensive retinopathy.
Stages of Hypertensive Retinopathy
Vasoconstrictive Phase: In this stage, the local auto-regulatory mechanism causes vasospasm and narrowing of retinal arteries.
Sclerotic Phase: Prolonged increase in blood pressure causes several changes in the blood vessel wall such as thickening of the intima layer, hyperplasia of the media layer and hyaline degeneration of the entire arteriolar wall. These changes result in widening and accentuation of light reflex, arteriovenous crossing changes, and arteriolar narrowing.
Exudative Phase: In patients with severe hypertension, the exudative phase is observed. It is distinguished by the disruption of the blood-brain barrier, disruption of the auto-regulatory mechanisms because of the leakage of plasma and blood into the vessel wall. In this phase, retinal signs occur like necrosis of smooth muscle cells, retinal hemorrhage, hard exudate formation, and cotton-wool spots.
Malignant Hypertension: Chronic intracranial hypertension results in ischemia of optic nerve and edema. Also, it leads to fibrinoid necrosis of choroidal arterioles. It causes segmental infarction of choriocapillaris leading to choroidopathy signs such as Siegrist’s streak, Elschnig’s spots, and Neurosensory RPE detachments.
Reversibility and Cure
Currently, treatment of hypertensive retinopathy includes close observation of the patients and correcting the underlying condition with the management of high blood pressure. To detect this condition, regular dilated fundus examinations are recommended.
Malignant hypertensive retinopathy is a clinical emergency and demands immediate attention with anti-hypertensive treatment. It should be noted that the rapid decrease in blood pressure can lead to impairment of autoregulation which can cause ischemia of the optic nerve head and other vital organs.
For some cases, administering injections to the eye can be helpful to control swelling of the retina. In patients with macular edema, injections can help to preserve vision. For those who have a retinal detachment, reattachment of the retina or its repair is carried out via surgery.
Manifestations of hypertensive retinopathy are reversible with proper management and control of hypertension. To evaluate the progression or resolution, close monitoring of patients every three to six months is recommended at the early or moderate stages of this condition.
What would a good eye-care specialist advise you?
It is possible to prevent hypertensive retinopathy with some lifestyle changes such as maintaining a healthy weight, limiting the intake of alcohol, managing stress, etc. The patients with hypertensive retinopathy should eat a diet low in salt and fat along with taking medications of hypertension regularly. It is always best to visit the best eye care hospital and consult a specialist for regular check-ups especially when you suffer from hypertension as many such conditions can be detected and treated early.
Figure 1. Fundus picture of a patient with hypertensive retinopathy. Cotton wool spots seen at the macula are a sign of ischaemia.
Figure 2. Fundus picture of a patient with hypertensive retinopathy showing optic disc edema, tortuous blood vessels, and macular edema.
Figure 3. Fundus picture of a patient with branch retinal vein occlusion
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