| Astigmatism results from the eye not being totally spherical in shape (like a football), but rather having one axis steeper than the other (like a rugby ball). This is not uncommon, with more than 95% of the population having some degree of astigmatism. The higher the level of astigmatism, the poorer the person's vision is if it is not corrected. |
Spherical: both axes
have the same curvature
|
Astigmatic: one axis
is steeper than the other
|
Although it was once considered more difficult to correct astigmatism with contact lenses than with glasses, this is no longer the case:
Soft contact lenses wrap to the shape of the eye like a glove and are therefore unable to correct astigmatism in their basic form. However, they can be made in a form, with one axis able to correct more refractive error than the other (called toric lenses). This type of lens needs more care in fitting than basic soft contact lenses as the angle and power of the astigmatic correction needs to be matched to that of the eye. These lenses are usually worn during the day only for two weeks or a month before being replaced. However, daily lenses of this type are to become available shortly.
Rigid contact lenses do not conform to the shape of the eye due to their rigid nature and are therefore able to correct low to medium levels of astigmatism in their basic form. For higher levels of astigmatism, they can be made with one axis able to correct more refractive error than the other. This type of lens needs more care in fitting than basic rigid contact lenses as the angle and power of the astigmatic correction needs to be matched to that of the eye. These lenses are usually worn during the day only and last for approximately one year. |
For more details contact your local BCLA contact lens practitioner |
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