Many people wear contact lenses as an alternative to eyeglasses to correct their vision. Astigmatism contact lenses differ from other types of contacts due to their irregular shape. They can be soft or rigid, and they also vary in terms of when and how long one can wear them before they must be replaced.
Contact lenses correct several types of vision problems, including nearsightedness, farsightedness, and astigmatism. While eyeglasses can usually also remedy all of these problems, many people prefer contacts for several reasons. Some advantages of contact lenses are their durability, their ease of use, and the fact that they can sometimes correct vision more effectively than glasses.
Astigmatism is a condition caused by an irregularly-shaped cornea. Some of the main characteristics include blurred vision and a distorted view of objects. People with astigmatism usually require toric contact lenses. A toric lens is curved to fit the unique shape of one’s cornea. Since people often experience either nearsightedness or farsightedness along with the astigmatism, the toric lens typically contains two different powers. One advantage of astigmatism contact lenses is that their unique design usually keeps them in place better than standard lenses. A potential disadvantage is that they are relatively more expensive.
Essentially, there are two types of toric lenses for astigmatism — soft lenses and rigid gas-permeable (RGP) lenses. Soft contact lenses are made of water and flexible plastics called hydrogels, both of which allow oxygen to reach the cornea. Another option that became available more recently is a silicone hydrogel lens, which allows even more oxygen to reach the cornea because of the silicone’s permeability. While regular soft lenses tend to conform to the shape of the eye, making them less effective at correcting astigmatism, soft toric lenses are specially designed to help improve one’s vision.
Rigid astigmatism contact lenses, on the other hand, are usually made of a combination of regular plastic and silicone, and they are only slightly flexible. They tend to retain their shape better on the eye, while also allowing oxygen to reach the cornea. Although the majority of patients prefer the comfort of soft lenses, some vision professionals recommend rigid lenses for what they consider to be superior vision correction.
Once someone has decided on soft or rigid astigmatism contact lenses, they can then choose lenses based on how often they have to be replaced. Some types include daily disposables, which are worn for one day and thrown away. Other contacts can be left in while sleeping and overnight. Some can be worn for several days or weeks, except when sleeping, and then replaced at regular intervals. Extended wear lenses can be worn for several days, including overnight. Yet, even these should still be removed once a week and replaced periodically. Continuous wear lenses can usually be worn for up to 30 days.
It is recommended that someone who wears astigmatism contact lenses has a proper professional fitting, and visits his or her eye doctor regularly to ensure that the contacts are working correctly. People with only a mild astigmatism may not need toric lenses at all. Standard lenses may be able to reshape the cornea just enough to correct the astigmatism, along with the nearsightedness or farsightedness for which they are also prescribed.