WHAT IS ASTIGMATISM OF THE EYE?

What is astigmatism?

The eye focus problem of astigmatism is due to the  shape of  your cornea and lens. If the red and green lines above reduce  to a point focus  clearer and more comfortable vision results. Accordingly refractive surgery,contact lenses and spectacle correction can also correct any eye focus problem you may have.

WHAT CAUSES AN EYE FOCUS PROBLEM ?

Astigmatism can be genetically inherited and develop in one or both eyes. In addition,eye strain and eye rubbing can alter the shape of the eye. Even your tear film can alter the quality of your vision. 

Exactly halfway between the red and green lines above is  where there is equal blur in both meridians.This is equal to the spherical equivalent, or best vision sphere. If the astigmatism is corrected the cross over point or focus can be on the retina. By contrast in myopia or short sightedness the focus is in front. In hyperopia or long sightedness the focus occurs behind the retina 
Focusing problems are evaluated by your  Ophthalmologist or Optometrist during your eye examination. Some irregular types such as keratoconus, can worsen over time. Excessive eye rubbing and some forms of eye surgery can also make some eye focusing problems worse. 

WHAT IS AN OPTICAL PRESCRIPTION?

A spectacle prescription contains the terms  “Sphere”, “Cyl”, and “Axis”. The positive sphere number (with a plus sign) indicates hyperopia and negative numbers (with a minus sign) indicate myopia.  The most common axis location on  the cornea or lens  is 180 degrees or so . This is referred to as “with the rule ”  or if around 90 degrees as “against the rule ” .Also the oblique type occurs outside this range. The irregular type  occurs when the meridians are not 90 degrees apart. 

HOW COMMON ARE EYE FOCUS PROBLEMS ?

astigmatism effects

Glasses or contact lenses have to correct in all directions.  Uncorrected  lens focusing errors  reduce visual acuity and eye comfort.

SEE MORE ON VISUAL ACUITY

How is vision corrected ?

Apart from contact lenses and glasses to correct vision, special contact lenses to reshape  the cornea can be used. Also  laser eye surgery techniques such as  LASIK, ASLA and SMILE can rectify some optical problems.
Sometimes optical errors can be overcome when the eye’s natural lens is removed and replaced with an artificial lens. However glasses or contact lenses may still be required to fully correct and balance the eyes 

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