Night blindness

Night Blindness is usually the first sign of Vitamin A deficiency. In this case the lesions in eyes are most obvious. Normally, people does not consume balanced diet due to which Night Blindness occur. Mainly, Vitamin A is found in the diet in 2 forms. The dietary sources of Vitamin A is animal derived foods such as yolk of eggs, butter, whole milk, fish, liver, kidney. Plants and Vegetables derived, dietary source of Vitamin A include carrots, potatoes, pumpkins, mangoes, spinach, B-carotene.

So deficiency of such elements in food may lead to development of night blindness. The main functions of Vitamin A, is that it helps in maintenance of normal vision in reduced light. This involves the synthesis of rhodopsin, a light sensitive pigment in the rods and cones of retina. This pigment then transforms the radiant energy into nerve impulses. Vitamin A or retinal also helps in maintenance of normal cartilaginous and bone growth.

Night blindness that occur due to Vitamin a deficiency, is common in countries of South-East Africa, Central and South America. Whereas malabsorption syndrome may account for conditioned Vitamin A deficiency.

Symptoms of night blindness

In case of Night Blindness, dry and scaly scleral conjuntiva is seen. It is known as Xerophthalmia. It occurs as a result of replacement metajplasia of mucus secreting cells by squamous cells. In case of Xerophthalmia there is less tear secretions from the tear glands from the tear glands and the eyes are noted to be completely dry. The lacrimal duct present in the eye, shows hyperkeratosis that is there is increased keratinization. Jin some patients, ulcers may develop in the cornea, known as corneal ulcers.

Further these corneal ulcers may get infected and lead to keratomalacia. These may also be Bitot’s spots visible which are in the form of focal triangular areas of opacities due to accumulation of keratinised epithelium. If the Bitot’s spots occur on cornea, then they inhibits transmission of light.

At the end, the infection, scarring and opacity leads to blindness. In addition to nigh blindness, Vitamin A deficient people may also suffer from cutaneous lesions, in which the skin develops popular lesions giving toad-like appearance and it is known as Xeroderma. This is chiefly due to follicular hyperkeratosis and keratin plugging in the sebaceous glands.

It is because very large doses of Vitamin A can produce toxic manifestations in children as well as in adults. The effects include headache, vomiting, stupor, etc. Hence, it is advisable to have adequate dosage of Vitamin A to prevent and teat night blindness.