Hypertension and the Eye

Hypertension and the Eye

(and cerebral haemorrhage too)

Guess which place in the body the arteries can be viewed directly and easily? Yep, that's right - in the eye! (Or more precisely, the optic fundi). The classification of Keith and Wagener is used to describe them.

OK, when you look down the opthalmoscope, you might be able to see the following:

Grade 1
Arteries become straighter and reflect light due to thickening of their walls (silver wiring). They may also show some variation in calibre
Grade 2
Because the arteries are thickened, they may also compress the veins at points where they cross each other (arteriovenous (AV) nipping)
Grade 3
In addition, flame shaped haemorrhages are seen along with soft (cotton wool) white exudates.(caused by areas of retinal infarction)
Grade 4
Swelling (papilloedema) of the optic disc may also occur

What you see will give some clues about a long and how severe the hypertension is.

Grades 1 and 2 may appear when people get older. It's when they appear prematurely that's important.
Grades 3 and 4 represent severe hypertensive change and often occur with malignant hypertension. This individual should be admitted to hospital for treatment.
Even in grade 4 hypertension there may be minimal or no upset in vision (but left untreated it might not stay that way).
Grades 3 and 4 changes usually disappear within a few weeks if they're given successful anti-hypertensive treatment.

THE RETINAL VESSELS

The retinal artery and vein run in the optic nerve and cross the subarachnoid space of the nerve sheath a short distance behind the eyeball. If the thin walls of the retinal vein are compressed, there's going to congestion in them, causing oedema of the retina, and bulging of the optic disc (papilloedema).

These retinal vessels mostly supply the bipolar and ganglion cells (which we will no doubt learn all about in the second year). The actual photoreceptors themselves are nourished by the capillary plexus in the choroid.

So what's the optic disc? Well, it's a region where you can see both the optic nerve leaving the eyeball and the retinal blood vessels entering it, through an opthalmoscope. If we want to be pedantic, it's 3mm medial to and slightly above the posterior pole of the globe. Oh, and another thing - you might already know it as the blind spot.

CEREBRAL HAEMORRHAGE

The most common cause of cerebral haemorrhage is hypertensive vascular damage. With prolonged hypertension, arteriosclerosis and small microaneurysms can develop, which predispose to vessel rupture, ending up in a haematoma. The common sites for hypertensive intracerebral haematoma are those supplied by the fine perforating vessels (deep in the brain) i.e. basal ganglia, internal capsule, thalamus, cerebellum and pons. Haematomas appear as a large blood clot, causing compression and damage to adjacent brain. Large haematomas in the basal ganglia and the thalamus often rupture into the ventricular system. Large bleeds that cause raised intracranial pressure, and those that rupture into the ventricular system, are usually fatal. (Not nice)

� 1997 Al Kam

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