Refractive Errors

 Refractive Errors

Refractive Errors is also called refraction error.

Refractive disorder is abnormalities of refraction that occur in eyes. Refraction results in the focusing of image on the retina of the eye, permitting vision. 

In refractive errors, vision is impaired because shortened or elongated eyeball prevents light rays from focusing sharply on the retina.

Blurred vision from refractive error can be corrected with eyeglasses or contact lenses.

Types of Refractive Errors 

1. Emmetropia

2. Ametropia

3. Myopia

4. Hypermetropia

5. Astigmatism

6. Presbyopia

1. Emmetropia

Emmetropia is normal optical vision condition of eye.

There is no error of refraction.

2. Ametropia

Ametropia is blurred or deformed vision when the image of the object does not form on the retina.

In Ametropia focus image formed either in front of behind the retina.

Types of Ametropia

There are 3 types of Ametropia;

1. Myopia or near-sightedness

Near sightedness is refractive error in which distant objects are fairly clear but images close up are blurred. 

In near sightedness distance between cornea and retina is too large. The image is formed in front of the retina.

So myopic person sees blurry at long-distance but well at short-distance.

Correction of myopia using convex lenses.

2. Hyperopia or Hypermetropia or far-sightedness

Hypermetropia in which distamt object are blurry seen but image closp are clear. 

In this case image is formed behind the retina.

Correction of far-sightedness using concave lenses.

3. Astigmatism

Astigmatism is imperfection or faulty in the curvature of eye's cornea or lens. 

In which curve of cornea, which is slightly oval instead of being round.

With astigmatism your vision is blurry or distorted at all distances.

Astigmatism is correct using corrective lenses.

3.Presbyopia

Presbyopia is the gradual loss ability of eye's to focus on nearby objects. 

This vision fault associated with aging, normal loss of near focusing eye ability, make near object seen blurry.

Correction of presbyopia using corrective lenses are using.