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Centration of toric IOLs
Toric IOLs are great choices for cataract surgery patients who have significant degrees of astigmatism. When the toric lens is properly aligned and centered, it can effectively treat the corneal astigmatism, resulting in improved vision for our patients.
 The corneal astigmatism tends to be centered over the pupil and visual axis, and not over the center of the cornea. |
The toric IOLs work best in patients who have regular, symmetric and stable corneal astigmatism. Patients who have irregular astigmatism, significant asymmetry or unstable corneas are not ideal candidates.
In borderline cases, a toric IOL may be a reasonable choice, depending on the situation and the patient's expectations.
We know that the toric IOL must be aligned with the correct steep axis of corneal astigmatism, but what about centration? The center of the cornea is not typically the center of the pupil, but most axis markings for toric IOL placement are at the limbus, thus denoting the corneal center. The visual axis is close to the center of the pupil but relatively far from the center of the cornea.
When we mark the axis of astigmatism at the limbus using a marking pen or a radial marker with a Mendez gauge, the line that connects our marks goes through the center of the cornea. Placing the toric IOL in alignment with these limbal marks would cause a decentration of the IOL with respect to the pupil, the visual axis and, most importantly, the centration of the corneal astigmatism.
When we place a toric IOL in the capsular bag, we need to ensure that it is aligned at the correct meridian and centered in the visual axis (or at least the pupillary center) in order for it to best correct the corneal astigmatism.
Get more expert perspective from Dr. Devgan live at Hawaiian Eye 2010, to be held January 17-22, 2010 at the Grand Hyatt Kauai. Learn more at OSNHawaiianEye.com.