Patients who underwent refractive surgery in its earliest form—radial keratotomy—need not always be denied premium IOLs, study finds. Image courtesy of Robert Ensley, OD, and Heidi Miller, OD.

Patients who underwent refractive surgery in its earliest form—radial keratotomy—need not always be denied premium IOLs, study finds. Image courtesy of Robert Ensley, OD, and Heidi Miller, OD. Click image to enlarge.

Lens power selection has been a subject of interest in radial keratotomy (RK) patients, as radial incisions disrupt the ratio of the anterior to posterior curvature and induce discontinuities in curvature across the surface of the cornea. This can alter predictions of effective lens position, cause overestimation of cornea power and produce irregular astigmatism. Looking into this issue, new research suggests toric IOLs can successfully treat corneal regular astigmatism in eyes that previously underwent RK and had toric IOLs implanted during cataract surgery.

In 40 eyes of 31 RK patients, preoperative corneal regular astigmatism was 2.10±0.98D. One eye had anterior corneal regular astigmatism of 0.50D or less, while two eyes had 1.00D or less. Compared with pre-op readings, the investigators found postoperative refractive astigmatism significantly decreased (0.46±0.44D) and the percentages of eyes with astigmatism of 0.50D or less and 1.00D or less notably increased. Specifically, 29 eyes (73%) had refractive regular astigmatism of 0.50D or less and 35 eyes (88%) had readings of 1.00D or less after cataract surgery and toric IOL implantation.

Additionally, the pre-op centroid value was 1.14D at 179°±2.05D. Following cataract surgery, vector analysis showed the centroid of refractive astigmatism after cataract surgery significantly decreased to 0.12D at 173°±0.63D.

Also of note: the standard deviation was markedly reduced from 2.05D to 0.63D, and no overcorrections were found in the study participants.

There is no research to show that surgically induced astigmatism from cataract surgery incisions in RK eyes is similar to that found in virgin corneas, the authors noted. The corneal incision may change astigmatism magnitude and vector differently than previously calculated in eyes without previous RK, and further studies are needed in this regard, they added.

Canedo ALC, Wang L, Koch DD, et al. Accuracy of astigmatism correction with toric intraocular lens implantation in eyes with prior radial keratotomy. J Cataract Refract Surg. August 18, 2021. [Epub ahead of print].