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Toric IOL rotation seen in eyes with long axial length
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Toric IOLs corrected preexisting corneal astigmatism and showed good overall long-term rotational stability after cataract surgery; however, significant IOL rotation was seen in eyes with relatively long axial lengths and with-the-rule astigmatism, according to study data.
Researchers prospectively studied 378 eyes of 302 patients with cataract and preexisting regular corneal astigmatism who underwent phacoemulsification and implantation of an Acrysof IQ toric SN6AT IOL (Alcon).
Uncorrected distance visual acuity, corrected distance visual acuity (CDVA), refractive cylinder and corneal astigmatism were reported preoperatively and at 1 day, 1 week, 3 months, and 1 and 2 years postoperatively. IOL misalignment and rotation were also evaluated.
Study results showed that CDVA was 20/25 or better in 305 eyes at 3 months. CDVA was worse than 20/25 in 17 eyes.
Mean refractive cylinder was −1.92 D preoperatively, −0.59 D at 3 months and −0.67 D at 2 years. Differences between preoperative and 3-month postoperative values were statistically significant, according to the researchers.
Mean IOL misalignment was 4.1° at 2 years. Mean IOL rotation was 4.5° within 1 day postoperatively.
Rotation was more than 20° in six eyes that had an axial length of more than 25 mm and with-the-rule astigmatism. All cases of rotation occurred within 10 days after surgery, according to the researchers.
Disclosure: The authors have no relevant financial disclosures.
Perspective
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Noel A. Alpins, MD, FACS
This paper discusses the incidence and causes of toric implant postoperative rotation in a large cohort of patients and eyes (378). The principal finding is that where rotation occurs to a large degree, it occurs within days of the initial surgery and has a definite association with long axial length and vertically orientated haptics when with-the-rule astigmatism exists. The likely cause is an associated large capsular bag, thin low-powered optic and possible excess viscoelastic left remaining after surgery.
The eyes and implant were examined physically and also mathematically. These parallel analyses revealed another interesting conclusion: although the mean physical position of the lens was 4.5° off +/- 5° and the arithmetic angle of error was only 1.7°, the absolute angle of error was 15° at 1 day postoperatively, with a large standard deviation of 30°. This suggests that the functional angle of error results of toric lens implantation can vary from the desired, even when the physical position of the lens is close to the intended site and the lens power is accurate (mean Correction Index of 1.02). This results in the remaining cylinder being significant in a proportion of cases.
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