While the vast majority of patients who undergo cataract surgery with PCIOL placement have excellent long-standing stable results, implant-related complications may occur, even when the IOL is placed in the capsular bag. Lenses may become decentered (ie, leading to edge glare) or they may rotate (ie, altering the astigmatic component of the refractive error in spherical and toric lenses). My colleagues and I encountered two cases of severe hyperopic shift following uneventful phacoemulsification and the placement of a collamer plate-haptic lens in the capsular bag.¹

CASE 1
A 69-year-old woman who exhibited a symptomatic cataract in her left eye underwent phacoemulsification without complications followed by the implantation of a CC4204BF +23.50-D collamer plate-haptic IOL (STAAR Surgical Company, Monrovia, California). One day postoperatively, she achieved a UCVA of 20/20. Upon examination after the first postoperative week, the uncorrected vision in the operated eye had dropped to 20/60, improving to 20/20 with a +1.25 D refraction. One month after surgery, the patient's uncorrected vision was 20/200, improving to 20/20 with a +2.00 D manifest refraction. The contralateral eye had also undergone cataract surgery with a similar power of the same IOL, allowing the patient to achieve an immediate and stable 20/20 uncorrected result. She was referred to my colleagues and I for evaluation.

The plate-haptic IOL was centered in the capsular bag, but appeared bowed posteriorly. The posterior surface of the IOL was positioned on the surface of the posterior capsule, while the intact capsulorhexis margin showed mild fibrosis without appreciable contracture and rested in a plane lying 1.5 mm in front of the anterior surface of the IOL. Minimal posterior capsular haze was observed. Funduscopic examination was unremarkable. No evidence of macular thickening, choroidal folds or staphylomata was detected in either eye. The IOL Master (Carl Zeiss Meditec AG, Jena, Germany) biometry was identical to the symmetric preoperative values.

Michael E. Snyder, MD, of the Cincinnati Eye Institute, in Ohio, proceeded by exchanging the implant for a three-piece acrylic PCIOL (+23.50 D Acrysof MA60AC; Alcon Laboratories, Fort Worth, Texas), placed within the capsular bag. The patient's postoperative uncorrected vision was 20/40 at day 1; 20/20 at 1 week; and remained stable at the 6-week follow-up visit with a final refraction of -0.50 +0.50 x 123.

CASE 2
A 72-year-old woman underwent phacoemulsification for her cataract with implantation of a +24.50 D STAAR CC4204BF collamer lens. Her uncorrected vision on the first postoperative day was 20/40 and improved to 20/30 with minimal refractive error after 1 week. Mild corneal edema and low-grade iritis persisted during the first month and were treated with Pred Forte and Acular (both Allergan, Irvine, California). Seven weeks postoperatively, her BCVA was 20/40 with a manifest refraction of +1.50 D, and the mild corneal edema and iritis had not improved. The surgeon noted that the anterior capsule was becoming increasingly phimotic and early posterior capsule opacification was developing. An optical coherence tomographer confirmed a normal macula without cystoid macular edema. At 6 months postoperative, the vision was correctable to 20/50+ with a manifest refraction of +2.50 -0.50 x 175. The patient was referred for evaluation.

Biomicroscopy revealed moderate guttata and a cell count of 2,310. The anterior segment was quiet and severe capsulophimosis was present with impressive stretch of the zonules. The PCIOL was within the capsular bag with moderate posterior capsule opacification. Axial length measurements and keratometry were similar in both eyes.

In the operating room, Robert H. Osher, MD, also of the Cincinatti Eye Institute, encountered severe capsulophimosis with secondary damage to the inferonasal zonules (Figure 1). The distal haptics of the plate IOL were curled anteriorly within the capsular bag, and the lens appeared ski-shaped (Figure 2). After performing a secondary anterior capsulorhexis — but failing at repeated attempts to reopen the fibrosed capsular bag — a peripheral iridotomy was made, and both the IOL and capsular bag were explanted and exchanged for an ACIOL. Information was obtained from the referring physician, and at 6 weeks the acuity reportedly measured 20/40 with mild but subsiding corneal edema. The manifest refractive error was +0.25 -1.00 x 95 and the IOL was well positioned.

SUMMARY
These cases illustrate a posterior movement of the IOL optic due to curling of the plate haptics within the capsular bag, causing an undesired hyperopic shift. Presumably, as the capsulorhexis became minimally fibrotic, the centripedal force of the lens epithelial cells was opposed incompletely by the centrifugal forces of the zonules and the haptics of the implant lens. As the collamer lens is highly flexible, the mild equatorial contraction may have resulted in a posterior bowing and, thus, a retroplacement of the optical portion of the lens. Depending upon the IOL power, significant hyperopia may be caused by even the slightest posterior displacement of the optic.

My colleagues and I are unclear as to why this occurred in only one eye in each case, despite the utilization of a virtually identical surgical technique in the fellow eye. We have wondered if prophylactic placement of a capsular tension ring may change the balance of forces acting on the equator of the capsular bag to reduce or eliminate a predisposition toward bowing of this highly flexible implant.

As interest in microincisional cataract surgery continues to mount, there is a tendency to seek out increasingly more flexible materials to insert or inject through an even smaller incision. The observations elucidated by these cases may have implications for other highly flexible implants under development (eg, rollable lenses). Further study of lens design features, biomaterials and perhaps the mechanical effects of capsular tension rings on the capsular fornix or pharmaceutical modifiers of capsular fibrosis may help to reduce or eliminate refractive shifts from lens bowing.

Faruk Ozturk, MD, is professor of ophthalmology at the University of Afyon Kocatepe, in Afyon, Turkey. He states that he holds no financial interest in any products or companies mentioned. Dr. Ozturk may be reached at drfaruk2@yahoo.com or +00 905334341863.

1. Ozturk F, Osher RH, Snyder ME. Progressive hyperopia after collamer lens implantation. Presented at the ASCRS/ASOA 2006 Symposium & Congress. March 19, 2006: San Francisco.