Refractive error, when left uncorrected is the most common cause of visual impairment. It is caused due to abnormal size and curvature of the eyeball.
Types of refractive errors
(1) Myopia or near sightedness
persons with myopia have blurred distant vision. Children with myopia arenot able to perceive their problem. It increases until the age of 20 or so. The condition can be corrected by concave / minus spectacles.
(2) Hyper metropia ( far sightedness)
persons with hyper metropia have difficulty in seeing both distant & near objects. The condition can be corrected by using convex / plus spectacles. When left uncorrected, such persons feel eyestrain and headache while doing close work.
In this condition, a blurred distorted image falls on the retina. It causes strain. This astigmatism condition is treated by wearing cylindrical glasses
After the age of 40, a person may find difficulty to see near objects clearly. This is because the plasticity of the lens decreases. The defect can be corrected easily by wearing spectacles.
Refractive errors cannot be prevented. However, they can be corrected with early detection and by wearing appropriate glasses regularly. There are mass screening programmes for detection of refractive errors among school children.
Parents / teachers can identify the refractive errors in children by observing