A 64-year-old man was referred to our clinic for analysis of residual refractive astigmatism following cataract surgery with toric IOL implantation in his left eye. As we were able to obtain his medical history, we knew the following: Preoperative biometry had been performed prior to the initial procedure using the IOLMaster (Carl Zeiss Meditec), and the toric IOL cylinder power and alignment axis were calculated based on automated keratometry (K) values from the same instrument (steep K, 49.30 D at 59º; flat K, 45.40 D at 149º). Standard phacoemulsification had been performed through a 2.2-mm limbal incision located at 100º, and a SN60T8 toric IOL (Alcon Laboratories, Inc.) with a spherical power of 18.50 D and a cylinder power of 5.25 D at the IOL plane aligned at 55º had been implanted. Expected residual astigmatism was 0.28 D. No intraoperative complications occurred.
At 6 weeks postoperative, the patient was referred to our clinic for analysis of residual refractive astigmatism. Distance UCVA in the treated eye was 20/400, and distance BCVA was 20/25 with a subjective refraction of +3.75 -5.75 X 135º. Slitlamp examination showed that the toric IOL was aligned at 143º (Figure 1). Scheimpflug imaging (Pentacam; Oculus Optikgeräte GmbH) demonstrated inferior steepening (Kmax 51.70 D); a central corneal thickness of 484 μm; and an inferonasal displacement of the thinnest corneal point, indicative of keratoconus (Figure 2).
Options available to correct residual refractive astigmatism following toric IOL implantation include repositioning the IOL and performing laser refractive surgery. We believe that the latter is most suitable for patients with low amounts of residual refractive astigmatism. In this case, because the toric IOL misalignment of almost 90º resulted in a large amount of astigmatism, we preferred to reposition the IOL by rotating it from 143º to 55º.
The timing of surgery is crucial in any realignment procedure to avoid formation of adhesions between the haptics and the lens capsule that cannot be dissected. To retract the distal haptic-end (ie, the knuckle) from its adhesion pocket, one pearl is to use a counterpressure technique, in which a fork is used to apply centrifugal force toward the bag circumference while a Lester hook is used to pull the haptic-end out of the pocket (eyetube.net/?v=wihen).
In this case, 1 month after the IOL was repositioned, distance UCVA in the left eye improved to 20/25 and distance BCVA was 20/20 with a subjective refraction of +0.25 D sphere.
This case demonstrates that preoperative corneal topography is mandatory in toric IOL implantation to rule out irregular astigmatism (in this case, caused by forme fruste keratoconus) and that repositioning of a misaligned toric IOL can be performed to improve distance UCVA and decrease residual refractive astigmatism. IOL repositioning should be performed as soon as possible—ideally in the early weeks after toric IOL implantation—to avoid formation of adhesions between the capsular bag and the IOL. However, as we have demonstrated in this case, with a meticulous surgical technique, repositioning of a toric IOL is still possible at a later time.
Rudy M.M.A. Nuijts, MD, PhD, is an Associate Professor of Ophthalmology in the Department of Ophthalmology at the Academic Hospital Maastricht, Netherlands. He is a member of the CRST Europe Editorial Board. Dr. Nuijts states that he has no financial interest in the products or companies mentioned. He may be reached at tel: +31 43 3877343; e-mail firstname.lastname@example.org.
Nienke Visser, MD, is a doctoral (PhD) student and resident in the Department of Ophthalmology at the Academic Hospital, Maastricht, Netherlands. Dr. Visser states that she has no financial interest in the products or companies mentioned. She may be reached at e-mail: nienke.visser@ mumc.nl.