defect is called Presbyopia. It arises due to the gradual (a), (b) The myopic eye, and (c) correction for myopia with a concave lens (a), (b) The hypermetropic eye, and (c) correction for hypermetropia N = Near point of a hypermetropic eye. N ’ = Near point of a normal eye. Think it over You talk of wondrous things you see, You say the sun shines bright; I feel him warm, but how can he Or make it day or night ?
– C. C IBBER Do you know that our eyes can live even after our death? By donating our eyes after we die, we can light the life of a blind person. About million people in the developing world are blind and most of them can be cured.
About . million people with corneal blindness can be cured through corneal transplantation of donated eyes. Out of these . million, % are children below the age of .
So, if we have got the gift of vision, why not pass it on to somebody who does not have it? What do we have to keep in mind when eyes have to be donated? Eye donors can belong to any age group or sex. People who use spectacles, or those operated for cataract, can still donate the eyes.
People who are diabetic, have hypertension, asthma patients and those without communicable diseases can also donate eyes. weakening of the ciliary muscles and diminishing flexibility of the eye lens. Sometimes, a person may suffer from both myopia and hypermetropia. Such people often require bi-focal lenses.
A common type of bi-focal lenses consists of both concave and convex lenses. The upper portion consists of a concave lens. It facilitates distant vision. The lower part is a convex lens.
It facilitates near vision. These days, it is possible to correct the refractive defects with contact lenses or through surgical interventions.