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Refractive error consequences of reversed-optic AMO SI-40NB intraocular lens
1Eye Specialists of Lancaster, Pennsylvania 17601, USA.
Objective:
To evaluate the refractive consequences of inadvertently implanting a reversed-optic AMO SI-40NB posterior chamber intraocular lens (IOL).
Design:
Retrospective case series.
Methods:
One surgeon (BLH) implanted 457 SI-40NB IOLs over a 2-year period beginning on January 1, 1996, and ending on December 31, 1997. Six of these IOLs (1.3%) were noted to have been implanted with a reversed optic. The authors retrospectively reviewed the target spherical equivalent refractive errors (SEREs) and actual postoperative SEREs for all 457 eyes.
Main Outcome Measures:
The SRK-II formula was used to predict target SEREs. Actual postoperative SEREs were determined at 1 month after surgery using either a manifest or an automated refraction. Target postoperative SEREs were subtracted from actual postoperative SEREs to calculate diopter surprises, or the degree to which the actual SEREs differed from the target SEREs.
Results:
The mean (+/-standard deviation) diopter surprise for reversed-optic SI-40NB IOLs was 0.01 (+/-0.89) diopter (D) more myopic than predicted; diopter surprises ranged from -1.39 D to +1.42 D. The mean diopter surprise for nonreversed SI-40NB IOLs was 0.18 (+/-0.81) D more hyperopic than predicted; diopter surprises ranged from -1.88 D to +2.56 D. The difference between the mean diopter surprises (0.19 D) was not statistically significant (t = 0.56, P = 0.57).
Conclusions:
A reversed-optic SI-40NB IOL is as likely to produce a satisfactory refractive result as a nonreversed IOL. Therefore, the refractive consequences of a reversed-optic SI-40NB IOL do not warrant the risks associated with repositioning the lens.