Irregular Astigmatism


Like regular astigmatism, irregular astigmatism occurs when light is bent by the cornea when it enters the eye but fails to focus clearly on a single point on the retina.  This results in blurred vision.  If light is bent in a uniform manner, it is called ‘regular astigmatism’ and can often be corrected by glasses and contact lenses but if the cornea has a bumpy surface, irregular astigmatism is caused.  Further, the following problems may be present:

  • The curve on one side of the meridian or axis is not symmetrical with the curve on the other side.
  • There are irregular patterns or differences in curvature and dioptric power within the cornea.

If there are bumps on the cornea, light passing through each of these bumps or ‘central islands,’ bends light a different way, which results in a distorted image being projected on the retina.  With big bumps, many blurred images can be projected upon the retina.  Multiple images can be found in each eye.  The medical term for irregular astigmatism is called ‘higher order aberrations,’ which describe and categorize these bumps on the cornea.

Irregular astigmatism may be caused by laser eye surgery and cannot be treated with glasses or surgery but gas permeable contact lenses may be an option.  Laser surgery can cause this problem if the surgery does not leave a smooth surface on the cornea.  The more uneven the surface is, the worse image vision will be.  It is difficult to fit contact lenses on such uneven corneal surfaces but they may be the only treatment option available.


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