Hypertension may be primary (essential) or secondary as in renal hypertension, toxaemia of pregnancy, etc. The vascular changes in the retina associated with elevated arterial pressure due to any cause depends on the resilience of the vessels and the duration of hypertension.
- Pathology: The essential vascular change is hypertrophy of the Tunica Media followed by fibrosis and hyalinisation leading to the narrowing of the lumen.
Grade I: The retinal sign consists only of arteriolar attenuation. Sclerosis of the retinal vessels which appear like copper or silver wires may or may not be there.
Grade II: The attenuation is more marked and the signs of sclerosis become recognisable at Arteries Venoms (AV) crossing. These AV changes include:
1. Gunns Sign-Apparent compression/ concealment of the veins.
2. Salus sign-a deflection in the courses of the vein.
Grade III: Together with the above changes soft exudates and retinal haemorrhages appear. Soft exudates appear as whitish, fluffy deposits with leathery edges lying superficially and obscuring vessels in the retina. Haemorrhages are superficial and flame shaped due to the arrangement of the nerve fibres whose fundus is edematous (wet retinopathy). Macular star or far in the macular region owing to the arrangement of the nerve fibre layer oedema tends to throw the retina into radiating folds arranged like the days of a star or a fan (when half).
Grade IV: Along with the above changes papilloedema appears (malignant hypertension). The blurring of the disc margin commences on the nasal margin and gradually spreads over the rest of the DISC. The prognosis for life at this stage is grave.
3. Management: Apart from the general management of the patient and anti-hypertensive drugs, no special management is required for the retinopathy as most of the changes are reversible with adequate control of the blood pressure.
Retinopathy of Toxaemia of Pregnancy
General features: Toxaemia of pregnancy usually occurs in the last three months (last trimester) and comprises the trial of hypertension, proteinuria and oedema. In its earlier manifestation it is known as the pre-eclampsia or pregnancy-induced hypertension. But when headache, vomiting and convulsion develop it is termed Eclampsia.
In general the retinal changes run parallel with the severity of hypertension. The clinical course of the disease may be divided into three stages:
- Stage of arterial spasm
- Stage of sclerosis
- Stage of retinopathy: Soft exudates, retinal oedema, etc.
- The general treatment consists of bed rest, sedatives and anti-hypertensive drugs.
- The role of the ophthalmologist lies in the discovery of early retinopathy so that pregnancy can be terminated to avoid maternal and neonatal mortality. Prognosis is usually good both for life and vision following termination of pregnancy.
Changes are as in hypertensive retinopathy. There is sclerosis, exudates, haemorrhages.
Central Vein Occlusion and Central Retinal Artery Occlusion
These are other two important manifestations that can occur due to hypertension.