About The Toric Single Focus Lens Implant
By David F. Chang MD
TORIC correction is one of the most common and popular features that can be incorporated into any artificial lens implant. It will benefit cataract patients with astigmatism who do not expect or intend to wear eyeglasses at all times. They are designed to improve how well you see without eyeglasses, such as in the distance, as compared to if you had a basic lens implant. There are 3 categories of artificial lenses for cataract patients to choose from: single focus (monofocal), extended focus(greater range than a monofocal, but not as much as the multifocal), andmultifocal (many continuous focal points). TORIC correction is a common feature that can be safely built into any of these 3 lens implant types.
What is astigmatism?
Like nearsightedness, astigmatism describes a common type of natural blur or misfocus in healthy eyes that is corrected by wearing eyeglasses. It results from an inherited, imperfect optical shape of the cornea, the clear front window of the eye. The shape of your cornea should be perfectly round, but if is more oblong (like the back of a spoon) instead of spherical, then it will misfocus details causing your natural vision to be blurrier compared to patients without astigmatism. The more astigmatism one has, the blurrier the vision is without eyeglasses. There is no benefit to having astigmatism because it increases natural blur at every viewing distance – far, near, and in between. Corrective eyeglasses compensate for this corneal shape to optically correct this blur and to optimally focus eyes with astigmatism.
Although it has nothing to do with cataracts, astigmatism can be nearly eliminated at the time that cataract surgery is done. By mapping your corneal shape in the office preoperatively with diagnostic testing called corneal topography, we can calculate the amount of astigmatism correction that your eye should require in eyeglasses for the clearest vision following cataract surgery. We can then build this amount of astigmatism correction into the artificial lens that is selected for your cataract surgery. This is called a TORIC correction and this feature will result in a more customized lens implant for your eye. During surgery, the surgeon positions the toric lens implant in a specific orientation to best neutralize the astigmatism from the cornea.
What will I see with a TORIC single focus lens implant?
The TORIC single-focus lens implant does NOT allow you to both read and see far away without eyeglasses. Many patients choose a TORIC single focus lens implant to provide good distance vision without glasses. Reading glasses would still be necessary but inexpensive (non-prescription) readers typically work well. Non-prescription sunglasses should also work well since the TORIC single focus lens functions as thought the prescription for distance eyeglasses is built into the lens implant. Alternatively, if a patient preferred to read without glasses, but wear glasses for distance vision, a TORIC single focus lens set for near can be used. Finally, compared to the basic (non-toric) lens implant, TORIC single focus lens implants improve the “depth of focus” for patients with astigmatism.
TORIC single focus lens implants may not necessarily correct 100% of your astigmatism either, especially if it is severe. However, compared to a basic lens implant that does not correct astigmatism, the toric lens implant should improve how well you see without glasses. Any eyeglasses that you do require should be less strong and potentially more comfortable to wear. Although astigmatism might infrequently increase slightly in some eyes with age, it won’t go away on its own and the benefit of the TORIC single focus lens implant should therefore be life-long.
Like contact lenses or eyeglasses, every artificial lens implant model (both basic and toric) is manufactured in more than 55 different powers. The appropriate power of the lens implant is estimated using mathematical models that utilize preoperative measurements of your eye’s dimensions. Although the measurements are very accurate, there are individual variables that prevent this process from being 100% perfect. If an “A” means perfect, your distance vision without glasses following surgery could be an A, or it could be an A- or B+. Thus, most patients will see quite well without glasses in the distance (assuming that was the target). However, if your distance vision without eyeglasses is a B+ (good but not perfect) you could choose to wear thin glasses with a mild prescription for those infrequent occasions when even sharper distance focus is required (to get an A).
Are there any disadvantages to TORIC single focus lens implants?
TORIC single focus lens implants pose no additional medical risk and are perfectly safe; they do not create nighttime halos or other optical side effects. They do not require the cataract surgery to be performed any differently and do not effectively lengthen the surgical time. Although the surgical recovery is no different, patients with astigmatism do see better with toric lens implants during the initial postoperative period when they have not yet received new prescription eyeglasses.
TORIC single focus lenses do involve additional costs, however. Health insurance, such as Medicare and PPOs, covers the costs of cataract surgery with a basic (non-toric) lens implant. However, the additional charge for implanting TORIC single focus lenses is not covered and must be paid out-of-pocket by the patient. Remember that the benefit of toric single focus lens implants is to improve your natural vision without eyeglasses. They are not “medically necessary” because they have nothing to do with your eye health. Because there are no side effects or drawbacks, aside from extra cost, TORIC single focus lens implants are an excellent and popular option when recommended by the cataract surgeon.