What is Refractive Error ?
Normally, your eye can focus an image exactly on the retina: Near sightedness and farsightedness occur when the focusing is not perfect.
When nearsightedness (myopia) is present, a person is able to see near objects well and has difficulty in seeing objects that are far away. Light rays become focused in front of the retina. This is caused by an eyeball that is too long, or a lens system that has too much power to focus.
” When farsightedness (hyperopia) is present, a person is able to see distant objects well and has difficulty in seeing objects that are near. Light rays become focused behind the retina. This is caused by an eyeball that is too short, or by a lens system that has too little focusing power.
Astigmatism is an uneven curvature of the cornea and causes distortion in vision. To correct this, a lens is shaped to correct the unevenness
With age, the lens in the eye becomes less elastic and loses its ability to change shape. This is called Presbyopia.
The loss of elasticity prevents the lens from becoming thicker. As a result, we lose the ability to focus on close objects. To correct this, bifocals are required. Bifocals are a combination of a lower lens for close vision (reading) and an upper lens for distance vision.
Correction of Refraction Error
Conventional and most known correction of refractive error is through glasses. For various categories of refractive errors such as nearsightedness (Myopia), farsightedness (Hyperopia) the loss of the ability to focus for near vision (Presbyopia), or abnormal curvature of the cornea (Astigmatism), prescription of eyeglasses can provide solution in most cases.
Disadvantages of Glasses
Although the main disadvantage of glasses is mainly inconvenience, the greater disadvantage is of frequent need of change in glasses. A direct collision on glasses by accident may cause permanent damage to the eye. Glasses with high power are a risk to users when it is lost or broken during travel or sports. Glasses do not allow you to enjoy your favourite outdoor sports.