Purpose: To describe reports of refractive hyperopic shift over time following intraocular lens (IOL) implantation, discuss possible etiologies, and suggest preventive and therapeutic treatments.
Setting: Multiple U.S. ophthalmic surgical centers; data collection at Staar Surgical, Monrovia, California, USA.
Methods: Forty cases displaying a progressive hyperopic shift in refraction after implantation of the single-piece Collamer IOL (Staar Surgical) were reported to the manufacturer out of 160 000 that have been implanted since its commercial introduction in April 2000. A retrospective data analysis of these 40 cases was performed; parameters included the mean refractive change over time, presence of capsular fibrosis, IOL displacement, and outcomes of secondary treatments. Individual case examples are presented.
Results: The mean refractive shift was 1.81 diopters (D) (range 0.25 to 3.75 D) with 5 cases (14%) demonstrating a hyperopic shift greater than 3.0 D. In 38 of the 40 cases, some combination of the following were reported: posterior displacement of the IOL, capsule fibrosis, and/or relief of the condition by performance of a radial or circumferential anterior neodymium:YAG capsulotomy to relieve capsule tension. The use of a small (less than 5.5 mm) capsulorhexis was also associated with cases showing the hyperopic shift.
Conclusion: The most likely etiology was the development of anterior capsule fibrosis, sometimes exacerbated by a small capsulorhexis, which could cause the IOL to move posteriorly, resulting in a hyperopic change in refraction. Previous in vitro testing by the manufacturer ruled out a change in the refractive power of the IOL in the eye as a cause of this phenomenon.