You may have heard that toric lenses are contact lenses for astigmatism, but what are they and why do they help? We walk through how these contact lenses work, and what to consider if you think you need them.
What are toric contact lenses?
A toric lens is a contact lens that's shaped in a particular way. Standard contact lenses have a spherical surface: think of a slice of the side of a beach ball.
A torus, in contrast, is a geometric shape that looks like a doughnut (the ring variety). A toric lens is shaped like a slice of the side of this doughnut.
The shape of toric contact lenses creates different refractive, or focusing, powers on the vertical and horizontal orientations. The refractive strength increases or decreases gradually as you move around the lens.
Contact lenses for astigmatism
Toric contact lenses correct for astigmatism issues that arise from a different curvature of the cornea or lens in your eye (referred to as regular astigmatism, corneal astigmatism or lenticular astigmatism).
In these cases, the cornea or lens is curved so that the refraction of your eye differs between the vertical and horizontal planes. This causes blurry vision and trouble seeing fine details. Sometimes, vertical lines will appear to tilt.
The ability for toric contact lenses to provide different refractive powers on the vertical and horizontal orientations addresses this specific peculiarity that causes astigmatism.
Choosing toric contact lenses
Toric contact lenses, like all contact lenses, need to be prescribed by your optician, who can choose the lenses that are right for your vision, and fit them for your eyes. Talk to your optician if you think you need contact lenses for astigmatism or other vision problems.
Meanwhile, here are some important things to consider:
Fitting is especially critical for toric contact lenses
Since toric contact lenses have a particular orientation, they need to stay on your eye in the correct way. Manufacturers design toric contact lenses with features to help the lenses stay put, including:
- Thin-thick zones
- Lens truncation, where the bottom of the lens is cut off a little
- Ballasting, where the lens is a little thicker or heavier
This means that the fitting the contact lenses to your eyes is even more important than usual. Toric contact lenses have a middle axis, like the Earth's equator, that keeps your line of vision clear. If your lenses don't fit well and slip, so does the visual clarity.
Different types of toric contact lenses
Toric contact lenses also address other visual corrections, and come in every wear schedule. You can have toric dailies and other disposable toric contact lenses - you can even have colour toric contact lenses.
Toric contact lenses are also made with both soft and rigid gas permeable (RGP), or hard, lenses. RGP lenses can be better at staying put, but also involve a longer initial adjustment time and can be drier and more delicate. Soft toric contact lenses are more comfortable and easier to manage, but need extra care in fitting to stay in place.
As with all contact lenses, chat with your optician about getting toric contact lenses for astigmatism. She can help you find the right correction and fit for both your eyes and your lifestyle.