Afyon, Turkey-A highly flexible posterior chamber Collamer lens may be problematic for some cataract surgery patients and require an exchange due to progressive hyperopia, explained Faruk Ozturk, MD.
Dr. Ozturk, of the University of Afyon Kocatepe, Afyon, Turkey, and his colleagues, Michael E. Snyder, MD (Cincinnati Eye Institute), Robert H. Osher, MD (Cincinnati Eye Institute and University of Cincinnati), and Joseph R. Bishop III, MD (Medical University of South Carolina), observed a posterior movement of the IOL optic (Collamer plate-haptic IOL, model CC4204BF, STAAR Surgical) implanted in two cataract surgery patients who developed hyperopia within a short time after implantation.
In the first case, a 69-year-old woman had received a +23.5-D plate-haptic IOL, placed in the capsular bag after routine phacoemulsification.
"The contralateral eye had undergone similar surgery with a similar-power lens and achieved an immediate and stable UCVA of 20/20," Dr. Ozturk explained.
He observed the lens to be centered within the capsular bag, however, the optic appeared to be bowed posteriorly.
"The posterior surface of the IOL was apposed to the surface of the posterior capsule," he said.
"The intact capsulorhexis margin showed mild fibrosis without appreciable contracture and rested in a plane lying 1.5 mm anterior to the anterior surface of the IOL."
The patient had minimal posterior capsular opacification (PCO). The fundus examination was normal.
Dr. Ozturk and his colleagues decided to exchange the Collamer plate-haptic IOL for a three-piece acrylic posterior chamber lens (AcrySof, Alcon Laboratories), also placed in the capsular bag. On postop day 1, a UCVA of 20/40 was achieved. By 1 week, the UCVA had improved to 20/20 and was unchanged at 6 weeks postop.
The second case
A 72-year-old woman also received the Collamer plate-haptic implant with a power of +24.5 D. The UCVA on postop day 1 was 20/40, which did improve to 20/30 at 1 week. However, the patient had mild corneal edema and low-grade iritis during the first month postoperatively. She was treated with prednisolone acetate (Pred Forte, Allergan) and ketorolac tromethamine (Acular, Allergan), but at the 7-week postop visit, best-corrected visual acuity (BCVA) was only 20/40 and the corneal edema and iritis persisted, Dr. Ozturk said.
Examination of the anterior capsule revealed phimosis and PCO. The patient's macula was normal with no evidence of cystoid macular edema, he continued.
At the 6-month postoperative visit, the patient was hyperopic with a manifest refraction of +2.5 –0.5 × 175. Her BCVA was 20/50+.
"Biomicroscopy revealed moderate guttata and an endothelial cell count of 2,310. The anterior segment was white and severe capsulophimosis was present with the impressive stretch of the zonules," Dr. Ozturk noted. "The distal haptics of the plate IOL were curled anteriorly within the capsular bag and the lens appeared to be ski-shaped."
An attempt was made to reopen the capsular bag without success. It was determined that the IOL and capsular bag be removed and an anterior chamber IOL inserted. The patient achieved a manifest refraction of +0.25 –1 × 95. These two cases demonstrate a problem of hyperopic shift when the plate haptics curled within the capsular bag.
"Depending upon the power of the IOL, even a small posterior displacement of the optic may result in significant hyperopia," he said. "We are unclear why in each case this occurred in only 1 eye, despite virtually identical surgical technique in the fellow eye."