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Astigmatism and toric lenses - what you should know

Let’s start with the point what astigmatism is.

As you may know, eye is an optical system made of 2 basic lenses - cornea and crystalens lens. Actually we have 3rd lens which is thin tear layer, but we will not take it into the equation now. Basically let‘s focus on cornea and a lens.

Cornea should be an ideally spherical, as ordinary football or basketball ball, to provide clear sharp image, which catched up by crystalline lens and focused on a retina.

But, quite ofter in human population, cornea has certain irregularities, and instead of being ideally spherical, cornea may have oval shape in one direction and its surface will look like a rugby ball. This irregularities disrupts image and thus retina gets unsharp and double image from different parts of cornea. This cornea abnormality called astigmatism and has to be corrected optically to keep image sharp.

To correct that optical imperfection, we may use so called toric lens, which has similar lens irregularity, which is placed opposite to cornea irregularity to compensate it. Actually image summation of cornea + lens will give a sharp and optically perfect image.

Why the lens is called toric? It has simple answer. While any optical lens is part of sphere, a lens which is intended to compensate astigmatism is made as part of another geometric figure called torus, thus lens is called toric.

So, if your eyes has significant amount of astigmatism, you definitely need a toric lens to compensate this for clear and sharp retinal image formation.

Toric lenses are not specific type of an IOL. Basically any IOL could be standard spherical or toric type. As toric component is a simply additional option to the lens geometry, like any car may have certain option or not, depending on its owner needs, but it will be basically the same car model.

Af your doctor say that you need a toric lens, it may be a case where you really need it for the best visual performance.

Toric IOL visually similar to ordinary lens, and just has specific marks on optical part to indicate direction of the optical irregularity, which has to be placed in a specific way based on your cornea irregularity direction. Your surgeon will investigate this, and install lens in a proper way during the surgical procedure.

Toric lenses are more expensive due to manufacturing and logistics specific, and its preside implantation requires more sophisticated instruments and more surgeon skills, therefore eye surgery in case of astigmatism and toric Intraocular lens implantation is generally more expensive. But it worth it, as if you have an astigmatism you definitely will have a better vision with astigmatism corrected versus non corrected option.

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