Definition of Anisometropia




Anisometropia is a refractive error in which there is a difference between the refractive powers of both eyes.


Anisometropia Causes


1- Congenital.

2- Developmental defects in which there is disproportional growth between both eyes.

3- Uniocular aphakia. It is acquired in which there was lens extraction from of the eyes due to many causes such as trauma, congenital cataracts. The aphakic eye will have high hypermetropia refractive power while the normal eyes will be within normal refractive powers.

4- After cataract surgery with miscalculation of intraocular lens power.



Types of Anisometropia


1- Simple Anisometropic Eye

Only one eye is affected while the other eye is normal. It is either simple myopic, simple hypermetropic or simple astigmatic anisometropic.

2- Compound Anisometropic Eye

Both eyes are either myopic, hypermetropia or astigmatic but with significant difference in the refractive power.

3- Mixed Anisometropic Eye

Both eyes have refractive errors but one eye is hypermetropic while the other eye is myopic .



Anisometropia Symptoms


1- Slight degree of Anisometropic error up to 2.5D is common and most of the time it is asymptomatic.

2- Significant difference more than 2.5 D can cause symptoms such as double vision and eye strain.

3- Uniocular vision in Anisometropic patient more than 2.5 D in which the patient will depend mainly on the good and ignore the abnormal high. This can cause amblyopia and strabismus if occurs early in age.



Anisometropia Treatment


1- Glasses

Which can be tolerable up to 4D difference.

2- Contact lenses

Can be used for higher difference but can cause significant difference in image magnification between both eyes.

3- Clear lens extraction

In eye with high myopic power, clear lens extraction can help to reduce the difference between both eyes.

4- Intraocular lens Implantation

In Uniocular aphakic patient, intraocular lens implant is the best treatment.

5- Treatments of complications

Children with anisometropia can develop amblyopia and strabismus. After treatment of refractive errors, treatment of anisometropic amblyopia and strabismus should be started.



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