Excessive intake of Vit A can lead to blindness in adolescents
— By Swapnil Mishra
Mumbai: While it is common knowledge that the deficiency of a vitamin can result in health problems, not everyone knows that the excess of a vitamin can also cause trouble. The accumulation of excess Vitamin A in the body can cause Stargardt disease, a condition characterised by progressive macular degeneration that culminates in blindness. This disease affects about 1 in 10,000 people. It is distinct from the macular degeneration observed in elderly persons.
Stargardt disease is an inherited disorder of the retina – the tissue at the back of the eye that senses light. The disease typically causes vision loss during childhood or adolescence, although in some forms, vision loss may not be noticed until later in adulthood. It is also known as Stargardt macular dystrophy, juvenile macular degeneration, or fundus flavimaculatus.
Dr K K Aggarwal, President Heart Care Foundation of India (HCFI) said vitamin A is beneficial for the eyes. However, when this vitamin builds up in one area of the eye, it can become toxic. This is what happens in Stargardt Disease where there is a build-up of Vitamin A in the retina. In time, this can cause progressive damage which ends up in partial blindness. The disease is caused by an inherited disorder in which Vitamin A accumulates in the eye and turns toxic. Dr Dheeraj, a senior ophthalmologist, said “The vitamin builds up in one part of the eye and becomes toxic. There is progressive damage that can lead to partial or complete blindness. For this reason, eye check-ups are recommended for children.”
Dr Aggarwal further added there are two types of photoreceptors rods and cones — in the retina. Together, they detect light and convert it into electrical signals, which are then ‘seen’ by the brain. Rods are found in the outer retina and help us see in dim and dark lighting. Cones are found in the macula and help us see fine visual detail and color. In this disease, both these photo receptors die away. Both cones and rods die away in Stargardt disease, with cones affected more strongly. Vitamin A is otherwise considered to be beneficial for the eyes, but in persons with this condition, it has the opposite effect. Early detection is the only way to save a patient’s sight. However, the symptoms are often misunderstood by parents.
They think that their child’s vision is deteriorating because of excessive use of mobile phones, computers, or because of watching too much television. Tell-tale signs of Stargardt disease include the loss of central vision in both eyes and the formation of hazy spots in one’s field of vision, increased sensitivity to bright lights and colour blindness.
Dr Aggarwal, said, “Currently, there is no treatment for Stargardt disease. Some ophthalmologists encourage people with Stargardt disease to wear dark glasses and hats when out in bright light to reduce the buildup of lipofuscin. Cigarette smoking and secondhand smoke should be avoided.”
Children and adolescents diagnosed with the disease are asked to wear dark glasses when they step out in bright light. They also asked to cut down on their intake of Vitamin A and to include more fish, green leafy vegetables and nuts in their diet. “Eat a healthy, balanced diet, including fish two to three times a week. Include leafy greens daily, a handful of nuts a week, and low GI carbohydrates. Minimize the number of fats and oils in the diet. Apart from this, ensure you get enough exercise regularly and maintain a healthy weight,” said Dr Satish Mehta.