1. Placement of Toric Intraocular Lens and the Long-term Change in the Axis of Corneal Astigmatism after Sutureless Cataract Extraction by Phacoemulsification Maggie Hymowitz MD, Maayan Keshet MD, Inna Ozerov MD, Marilyn Ilan ASOT, Leslie Shapiro MD The authors have no financial interest to disclose

2. Purpose Astigmatism is common in patients undergoing cataract surgery. Between 15% and 29% of cataract surgery patients have more than 1.50 diopters (D) of preexisting astigmatism. 1 Correction of corneal astigmatism is important for improving visual outcomes following cataract surgery. The FDA-approved, one-piece hydrophobic acrylic toric intraocular lens (IOL), offers this option. Accurate toric alignment is crucial for effective refractive correction with toric IOLs.

3. Purpose Recent studies have shown that the acrylic IOL is very stable, with a mean IOL rotation of 3.35° in one study and 3.63° in another study. 2,3 Given such excellent rotational stability in patients with pre-existing corneal astigmatism, this lens has recently gained popularity. In our retrospective chart review, we examined the degree to which the axis of corneal astigmatism changes after cataract surgery. Post-operative rotation could have a bearing on axis calculations for the toric IOL.

4. Methods Fifty patients who underwent cataract surgery by a single surgeon between 1998 and 2004 were identified thorough a computer-based patient registry. The surgeon used a 2.6 mm temporal clear corneal incision and a two-handed phaco-emulsification technique. The registry included the patients’ ages, surgical techniques, and pre- and post-operative keratometry measurements at regular time intervals from 1 day to approximately 6 years post-operatively. Patients with previous corneal surgery, corneal astigmatism less than 0.75 D, complex cataract surgery, or operative complications were excluded from the study.

5. Methods Patients with pre-operative corneal astigmatism ≥ 0.75 D and no intraoperative complications were identified. Corneal astigmatism was assessed using an automated keratometer. The keratometric cylinder values were calculated from the measured radius of curvature.

6. Results Thirty eyes were included in the study. The average age was 75.6. The average change in axis pre and post-operatively (3-6 years) was 13.27°. (p=0.194) In 13 patients (43%) the axis rotated toward the 90 degree axis. In the remaining 17 patients (57%) the axis rotated toward the 180°.

7. Results The association of axis-change with pre-operative age was not statistically significant (r=0.14). The association of axis-change with average preoperative K-readings was not statistically significant (r=0.04). The average change in cylinder value before cataract extraction and 3-6 years after surgery was -0.25 D, also not significant (p=0.41).

8. Conclusions Although the statistical analysis indicates that pre- to post-operative axis change was not significant, clinically, 13.27° of toric IOL rotation would mean an almost 40% loss in the astigmatic correction. 4 However, the direction of axis change was unpredictable and therefore unhelpful in pre- operative planning of toric IOL placement.

9. References 1. Hoffer KJ. Biometry of 7,500 cataractous eyes. Am J Ophthalmol. 1980;90:360–368. 2. Chang DF. Comparative rotational stability of single-piece open-loop acrylic and plate-haptic silicone toric intraocular lenses. J Cataract Refract Surg. 2008;34:1842–1847. 3. Mendicute J, Irigoyen C, Aramberri J, Ondarra A, Montés- Micó R. Foldable toric intraocular lens for astigmatism correction in cataract patients. J Cataract Refract Surg. 2008;34:601–607. 4. Viestenz A, Seitz B, Langenbucher A. Evaluating the eye's rotational stability during standard photography: Effect on determining the axial orientation of toric intraocular lenses. J Cataract Refract Surg. 2005;31:557-561.