Astigmatism

• Astigmatism is a type of refractive error causing blurred vision. It is the result of an irregular corneal surface or an irregular curvature of the lens or a combination of both. Basically, the eye is shaped like an end of a football instead of being spherical. Light passes through these curvatures and hits at two different points in front of or behind the retina depending on whether the eye is also near or farsighted. Visual correction through glasses or toric contact lenses brings these points together and focuses them on the retina. Symptoms of astigmatism include blurred or distorted vision, headaches, eyestrain and fatigue.
  
  

Toric contact lens vs. Toric XR contact lens

• The "XR" notation on a contact lens simply denotes "Extended Range" meaning it will correct more astigmatism than a regular toric contact lens. For example, one common brand of toric contact lenses will correct +6.00 to -8.00 diopters of near or farsightedness and up to 2.25 units of astigmatism. The same brand in the XR version will correct +6.00 to -8.00 diopters of near or farsightedness and up to 5.75 units of astigmatism. The XR version is used for patients with higher levels of astigmatic correction.
  
  

Fitting a Toric or XR Toric Contact Lens

• Correct for vertex distance, the distance from the patients' eyes to the spectacle plane. Round the prescription down to the nearest available cylinder power. Round to the nearest cylinder axis. Finally, when choosing the trial lens assume there will be no rotation and choose the closest axis to the refraction. With a toric lens the position of the lens is very important. It must stay in place and keep the same orientation regardless of eye movement. Determining how much astigmatism needs to be corrected is crucial in determining whether you will need a regular toric lens or an XR toric lens.
  
  

Toric Options

• Regular toric contact lenses are available in more options. They are available in a daily, weekly or monthly disposable, an extended wear (overnight) version, a multi-focal version and they are even available in colors. The XR lenses have a more limited availability because they are a more custom product. These lenses are typically available in only a yearly or quarterly replaced modality. The XR lenses are not available in an extended wear version. There is limited availability of an XR lens with multi-focal capability. They are not available in colors.