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Stan Bentow, Sanjeev Kasthurirangan; Intraocular lens power determination for a new extended range of vision lens. Invest. Ophthalmol. Vis. Sci. 2017;58(8):1147.
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© ARVO (1962-2015); The Authors (2016-present)
Intraocular lens (IOL) power calculations can be performed using one of several equations which vary in the number of preoperative factors considered and inherent empirical regression adjustments. For newer IOL designs, such as extended range of vision IOLs, the performance of these power equations is not well known. In this study, we wanted to evaluate power calculation for a new extended range of vision IOL using a purely statistical approach.
Retrospective analysis was performed on 6-month postoperative data from a multi-center (15 clinical sites), randomized, subject/evaluator masked clinical investigation on 299 subjects implanted bilaterally either with the TECNIS Symfony Extended Range of Vision (ERV) IOL (148 subjects) or the parent monofocal control IOL (151 subjects). Statistical stepwise regression of numerous preoperative factors was performed to identify contributing factors to the IOL power that would lead to emmetropia. Analysis was done for the ERV and monofocal groups independently and compared between IOL groups for similarity of trends. None of the available IOL power equations were used in this analysis to avoid any inherent bias or assumptions in the various IOL power calculation formulae.
Axial length, mean keratometry, age, keratometric cylinder and anterior chamber depth were the variables statistically significantly associated with IOL power for the monofocal lens (p<0.05, r2 = 0.93). Axial length, mean keratometry and age were the variables statistically significantly associated with IOL power for the ERV lens (p<0.05, r2 = 0.88). Data fit using only parameters common to both IOL groups from the stepwise regression, yielded similar parameter estimates (Table 1). In addition, post-operative refractive error was similar for monofocal (mean ± SD: -0.37 ± 0.42 D) and ERV (-0.40 ± 0.39 D) IOL groups.Table 1: Parameter estimates for IOL power for emmetropiaParameter Symfony MonofocalAxial Length -3.13 -3.17Mean K -1.11 -1.18Age -0.02 0.01**Not statistically significant (p>0.05)
Relative contribution of preoperative factors to determine IOL power was similar between an extended range of vision lens and its parent monofocal IOL. Power calculation for the extended range of vision IOL can be performed in the same fashion as the parent monofocal lens.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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