Among various vision deficiencies, the most common are myopia, hyperopia and presbyopia.Generally speaking, you are able to see because the front part of the eye directs the light to the retina located at the back of the eye. Once the light is not focused exactly on the retina, the perceived image becomes blurred.
Myopia, commonly referred to as near-sightedness is caused by incorrect focusing of the light when entering the eye, making distant objects appear as blurred. Myopia occurs when the focus of the light rays falls before the retina. Consequently, the light rays are not focused on the retina and the images you see become blurred. Usually, squinting makes distance objects seem clearer for myopic eyes. Myopia is a type of refractive error of the eye, equally affecting males and females. It is often first found in school-aged children or teenagers and progresses with the development. Children often cannot read the blackboard, but they can easily read a book. Those who have a family history of myopia are more likely to develop it.
Hyperopia, commonly referred to as far-sightedness, is manifested as a difficulty in seeing near objects compared to distant objects. Symptoms may also include aching eyes, crossed eyes (strabismus) in some children, eye strain and headaches while reading. Hyperopia is caused by incorrect focusing of the light behind the retina rather than directly on it. It may be caused either by the eyeball being too small or the focusing power being not strong enough. Hyperopia is often appears at birth, but usually disappears during development until school age. However, if it remains, glasses or contact lenses are usually required to correct the vision. Those who have a family history of hyperopia are more likely to become farsighted.
Aging affects several functions of our body, one of which is the eyesight. Presbyopia is a common vision deficiency which occurs starting from around the age of 40 and is eventually found in everyone by the age of 51. It is a result of natural deterioration in the focusing ability of the eye. The ability of the lens to modify its shape is termed the elasticity of the lens. This elasticity is slowly degraded as people age. The result is a incremental reduction in the ability of the eye to focus on close objects. Presbyopia, sometimes referred to as the “short-arm syndrome”, may lead to eye tiredness, blurred near vision and headaches – physical inconveniences that have troublesome effects on the lives of millions around the world.