Dziram Eye Center

Refraction and prescription of optical Lenses
Refraction

To make our eye health care complete, we offer services for refraction and prescription of lenses.
If someone does not see very well but seems to have a normal eye, there is the likelihood that the person has a refractive error. If you have to squeeze your eye before you see well or if your child has to sit close to the TV or hold his book very close to read it, then it could be that you or your child has a refractive error.

Refractive error is not a disease but a state or condition of the eye. The common types of refractive errors are presbyopia and myopia.
    

 

                                  

-Near or shortsightedness or Myopia:
As shown above, if a person is near or shortsighted, it could be due to the fact that his eyeball is longer than normal or the refractive power of his cornea or lens are very high. This causes light entering the eye to be focused sharply before the retina, making the picture which falls on the retina blurred. A minus or concave lens can be used to correct this refractive error to push the light rays to a sharp focus on the retina.
It is worth mentioning here that some people have progressive myopia, with the refractive error increasing progressively every year. Such people (with refractive error of -5.00 D and above) have a risk of developing retinal detachment over time. They thus need to have their retina or fundus checked at least once every year (dilated fundoscopy) to prevent this as early changes could then be detected and treated appropriately.

-Hyperopia (Far-sightedness)
As shown in the diagram above, normal vision occurs when light from outside is focused sharply on the retina after passing through the cornea and the lens. The cornea and the lens constitute the main refractive structures which bend or change the direction of the light to focus sharply on the retina. If someone is hyperopia or far-sighted, light passing through the cornea and lens are bent or refracted to focus behind, instead of on the retina. This could happen either because the eyeball is too short or the refractive power of the cornea and lens is too weak. Such a person needs a plus or biconvex lens to correct his or her vision.

-Presbyopia
The lens in the eye is held by several tiny strings (zonules) which are attached to a muscle called the ciliary body. Contraction and relaxation of this muscle pulls on the lens to change it's shape so that the lens can change it's focus to bring objects which are far or near to a sharp focus on the retina. This phenomenon is called accommodation. However as one grows older, usually pass the age of 35years upwards, the lens becomes a bit more rigid and the ciliary muscles also become less elastic than they used to be. This reduces the range of accommodation and one begins to have difficulty focusing on things close to him or her.  This is what is called presbyopia and once that begins, you will see that you have to take things a bit further away from you before you can read them. When that happens, it means it is time for you to get some reading glasses. It does not mean your vision is getting weaker. It is something which comes with age and shows that you are becoming ' a big person'. This is because most ‘big people’ carry reading glasses and take it out if they have to read or sign something!


Dziram Eye Center Introduces vitreo-retinal surgery from September 2012...