The normal blood pressure is a function of two measurements: the diastolic and the systolic blood pressure measurements. The diastolic is measured in between two systolic beats, when the heart muscles are relaxed. The normal diastolic value ranges from 60-90mmHg. The systolic is measured when the heart muscle contracts followed by a beat. The normal systolic value ranges from 100-140 mmHg. A ratio=
Systolic/Diastolic (mmHg) defines the arbitrary blood pressure.
An indivudual is said to be hypertensive when his systolic is consistently equal to and/or above 140 mmHg with a consistent diastolic reading of 90 mmHg and above.
Like other cardiovascular conditions, hypertension has strong affinity for blood vessels especially the capillaries. Arterisclerosis and arteriolosclerosis are major cardiovascular changes that is associated with chronically elevated blood pressure.
The eye is surrounded by end blood vessels, i.e. blood vessel with terminal roots in the eye. The retina, the uvea and the optic nerve areas are vascularized areas of the posterior eyeball. They are made-up of tiny arterioles susceptible to chronic hypertension. The chronicity and management of systemic hypertension determines how most ocular symptoms of the disease manifest. And the vascularized parts of the eyes are frequently affected more often than the non-vascular portions of the eyes. For instance, the retina is more affected in systemic hypertension than by the non-vascularized cornea.
The retina and the choroid are the earliest to start showing signs of systemic hypertension. Thinning of retinal vasculature, nicking of retinal vessels, deep seated choroidal vascular changes and oftentimes background hypertensive retinopathies. This patient complains of reduced visual acuity both far and near especially in the adult population. The resulting refractive error is often a hyperopic shift. One will expect increased crystalline lens sclerosis in adult hypertensive patients.
Poorly managed or unmanaged systemic hypertension causes more dramatic ocular complications. The retina, the choroid, the optic nerve and the surrounding vitreous body casts varying signs and symptoms that complicates visual acuity. The retinal sensitivity is severely reduced in cases of proliferative hypertensive rethinopathy. Retinal haemorrahge is not uncommon in very poorly managed systemic hypertension. Chronic and unmanaged hypertension could cause serious choroidal vascular complications which often results in low vision or even blindness.
As a primary health care specialist, it is required of us to always place emphasis on the rouine BP check for our patients even without complementary ocular symptoms.Every patient with hypertension should be periodially visually examined to rule out potentially blinding signs associated with long standing hypertension. Refer every hypertention patient you come in contact with to the nearest medical centre while encouraging healthy living viz exercises, dieting and periodic medical check-ups etc...
