Toric Lens Implant: Correcting Astigmatism During Cataract or Lens Replacement Surgery

Many people who need cataract surgery or refractive lens exchange also have astigmatism. A standard intraocular lens does not correct it, so vision can remain blurred without glasses after an otherwise successful operation. A toric lens implant builds astigmatism correction into the new lens.

This page explains when a toric lens is worth considering, how it is measured and aligned, what happens if it rotates, and the alternatives. For all lens options, see lens replacement surgery.

Cataract surgery with astigmatism: why does it matter?

In astigmatism, the clear front window of the eye (the cornea) is curved more steeply in one direction than the other, more like a rugby ball than a soccer ball. Light is focused at two different points, so vision is blurred or stretched at every distance.

The eye's natural lens can add some astigmatism of its own, but it is removed during surgery, so what the new lens has to correct is the astigmatism of the cornea. Left untreated, it can mean glasses for distance as well as for reading, and it reduces the benefit of presbyopia-correcting lenses, whose aim is vision without glasses.

European guidance (ESCRS, 2024) recommends considering a toric lens when corneal astigmatism is 1.0 diopter (D) or more, and rates the evidence as strong above 2.0 D and moderate above 1.5 D. Smaller amounts can often be managed in other ways (see the alternatives below).

How does a toric lens implant work?

A toric lens combines two corrections: the spherical power that every intraocular lens has, and an extra cylinder power in one direction that cancels out the corneal astigmatism. Small marks on the lens show the direction of this extra power. During surgery the lens is rotated inside the lens capsule until the marks line up with the planned angle, which matches the steepest curve of the cornea.

A toric lens corrects regular astigmatism, which has a symmetrical pattern. It is not suitable for irregular astigmatism caused by keratoconus and other forms of corneal thinning (ectasia), or by corneal scars.

How are the measurements and alignment done?

Toric lens planning depends on precise measurements:

• Corneal topography or tomography maps the shape of the cornea, measuring the amount and direction of astigmatism and confirming that it is regular; ESCRS includes it in the work-up when astigmatism is present.
• Optical biometry measures the length of the eye and the curvature of the cornea; NICE recommends it for calculating lens power.
• The tear film is checked first, because an unstable tear film can distort corneal readings; ESCRS recommends diagnosing and treating dry eye before surgery.
• The calculation combines these measurements to choose the cylinder power and the exact angle of placement.

On the day of surgery, reference marks are usually made on the eye while you sit upright, because the eye can rotate slightly when you lie down, or an image-guided system is used instead. At the end of the operation the lens is turned to its planned angle, and its position is checked at follow-up visits.

What if a toric lens rotates?

A toric lens works only if it stays at its planned angle. EyeWiki, the American Academy of Ophthalmology's online encyclopedia, notes that for one widely used toric design the correction falls by about 10% for every 3 degrees of rotation, roughly 3.3% per degree. A lens sitting 10 degrees off its planned angle therefore loses around a third of its astigmatism correction.

Rotation is more of a concern in eyes with weak lens supports (zonules), a torn lens capsule, a pupil that does not dilate well, or previous retinal or glaucoma surgery, which EyeWiki lists as relative contraindications. If a lens has rotated enough to matter, it can usually be turned back into position in a short second procedure, and any remaining astigmatism can be corrected with glasses or laser treatment.

Are toric versions available for monofocal, EDOF and trifocal lenses?

Yes. Most lens platforms come in toric versions, so astigmatism can be corrected whichever lens family you choose:

• toric monofocal lenses, for sharp vision at one distance, with glasses for other distances;
• toric EDOF lenses, for example a toric version of TECNIS PureSee for astigmatism of 1 D or more;
• toric trifocal lenses, for example ZEISS AT LISA tri toric, which its manufacturer offers for cylinder powers from +1.0 to +12.0 D.

With presbyopia-correcting lenses, accurate astigmatism correction matters especially, because the aim is good vision without glasses at several distances; irregular astigmatism calls for caution with multifocal lenses. See trifocal lenses and EDOF lenses. The lens names above are market examples, not the lenses used at this practice.

What are the alternatives to a toric lens?

• Incision placement. For small amounts, the main incision can be placed on the steep axis ("on-axis" surgery), or limbal relaxing incisions can be made at the edge of the cornea; NICE suggests considering these to reduce astigmatism.
• Laser arcuate incisions. In laser-assisted cataract surgery, the femtosecond laser can make curved (arcuate) incisions in the cornea to reduce astigmatism.
• Glasses or contact lenses after surgery.
• A light-adjustable lens, whose power, including up to about 3.0 D of cylinder, can be fine-tuned with UV light after surgery; it requires several visits over a number of weeks.

Which approach fits depends on the amount and type of astigmatism and on your choice of lens; see how to choose a lens.

Toric lens planning in Antalya

Prof. Türkoğlu assesses the shape of your cornea and the health of the whole eye, explains whether a toric lens is advisable, and plans its power and position with you. A toric version usually adds to the cost of the lens; see lens replacement cost.