Contact lenses for astigmatism
Astigmatism is a refractive error that is almost as common as myopia. It affects a large number of people who as patients need special types of contact lenses or glasses to correct their vision. It occurs when the cornea is not spherical but more toric in shape. The result of which is that the image on the retina is unclear and often described by patients as a 'halo' effect on the edge of objects.
Fortunately the condition has always been fairly easy to correct with glasses but it used to cause some problems when contact lenses were first used. This was associated with difficulties achieving appropriate stability (important because of the irregularity of the astigmatic cornea). Basically the lens would rotate or move off centre.
Fortunately, modern designs have eliminated the stability issue, so while wearing modern astigmatic contacts, patients can enjoy the same acuity of vision as people with myopia. In addition, astigmatic patients have a number of excellent options to choose from – including various types of materials (rigid gas permeable, hydrogel, silicone hydrogel ones), modalities (from daily disposable contact lenses to monthly ones) and sizes (with different curvature and diameter). Over the last few years another innovation became available: coloured toric contact lenses, which not only correct advanced vision problems but also alter one's eye colour.
Patients with common types of astigmatism can be fitted with contact lenses immediately. Those with more complicated cases might have to wait for lenses custom made to their refractive errors but the ultimate results are virtually identical: crisp and clear vision without the need to wear glasses.
Should I get spherical or toric contacts for correcting my astigmatism?
Even though there's a lot of toric contact lenses to choose from at the moment, interestingly there's still the option to use regular spherical contact lenses to correct the vision of people with astigmatism.
Spherical contacts are not designed to correct astigmatism. However since they are much cheaper, very easy to fit, provide very good visual acuity in patients with low levels of astigmatism and do not cause rotational problems, they are often chosen by patients that have only very slight astigmatic correction needs but other vision correction issues.
Toric contact lenses, on the other hand, are indispensable when the level of astigmatic correction required is high. What is more, they generally provide better vision even when astigmatism is low because of the reduction of the 'halo' effect.
The dilemma that both patients and practitioners need to deal with is at which point it is necessary to switch from spherical to toric contact lenses. According to most experts, the threshold is usually 0.75D of astigmatism. Higher levels usually require toric lenses and for lower levels of correction spherical contacts are generally sufficient. Of course, it is ultimately the patient's choice, since some require the best possible visual acuity (also for occupational reasons) and some opt for convenience. Our advice on this is that if you are near the threshold, try both. Under different situation or activities they may both have advantages.
