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# Is it necessary to have a bigger eye ball for developing Myopia ?

Feb 25, 2018

Myopia is defined as a refractive error,where parallel light rays coming from infinity,after getting refracted meets in front of the neurosensory layer of retina with accommodation at rest.

But it is not necessary that a myopic eye has to be bigger in size.

Basically,myopia can result from the following cases,

1 . AXIAL MYOPIA : This a condition where the eye ball is larger in size due to faulty (limitless) growth during the development,as a result normal visual axis of $24 m m$ is increased and after refraction light falls in front of retina.

2 . CURVATURAL MYOPIA : This is a condition where,corneal curvature is increased than normal(i.e radius of curvature is decreased),as a result,refractive power of cornea increases and light rays meet,infront of retina.

3 . POSITIONAL MYOPIA : This is a condition where,the lens is abnormally placed infront of its normal location,as a result focal point is found in front of the retina.

4 . INDEX MYOPIA : This happens in old age(associated with cataract),when the refractive index of lens increases,resulting in increased power of lens,so that light rays meet infront of fovea.

Now,the above classification is etiological classification,there is another clinical classification as well,which has three subtypes,

A . Congenital Myopia

B . Developmental Myopia

C . Pathological or degenerative Myopia

Some important Symptoms are :

1. Blurring of vision

2. Asthenopic symptoms

3. Half closed eyes in order to allow parallel light rays passing only.(basis of pin hole test)

Some important signs are:

1. Deep anterior chamber

2. Papillary Crescent formation surrounding the optic disc

3. Foster Fuchs spot(due to stretching of choroid as occurs due to retinal enlargement results in subretinal hemorrhage)

the last two are found with the help of fundoscopy.

Treatment :

OPTICAL : Using concave lens in glass or contact lens,once the power is adapted properly.

SURGICAL : Using Photorefractive Keratotomy, LASIK (LASER in situ Keratomileusis)

Surgical correction of myopia is very popular now a days than optical correction.