A retrospective analysis of five intra-ocular lenses and the predictive value of six different intra-ocular lens power calculation formulas.

Purpose: To evaluate the refractive and visual outcome after implantation of five different lenses and to evaluate the accuracy of six different intra-ocular lens (IOL) power formulas.

Setting: Department of Ophthalmology, University Medical Centre Rotterdam, The Netherlands.

Methods: In total, 288 eyes had cataract surgery with implantation of a polymethylmethacrylate lens (Centra55B) or a foldable silicone lens (AMO SI40, Staar AA, Silens 5, Pliolens). The pre- and postoperative refraction and visual outcome were analysed for all lenses under study. Six different IOL power formulas have been used to compare the accuracy of the predictive refractive outcome.

Results: The Staar Plate Haptic lens was found to have the best uncorrected visual acuity (UCVA) compared to the Centra55B, AMO SI40 and the Pliolens. Based on the A constant given by the company, the Pliolens revealed a significant overcorrection and the Staar Plate Haptic lens an undercorrection. The achieved postoperative refraction minus the intended postoperative refraction caused significant myopia with the Pliolens and hyperopia with the Staar Plate Haptic lens. The SRK-T and the Holladay formulas give the best predictive lens calculations in relation to the axial length.

Conclusion: The A constant of all lenses has to be adjusted for our institute. Especially the AMO SI40, the Staar AA lens and the Silens 5 showed a remarkable difference compared to the A constant given by the company. All foldable lenses were comparable in their visual outcome. The significantly better UCVA of the Staar Plate Haptic lens can be explained by the emmetropic outcome of the postoperative refraction.