Reflection on refraction in multifocal intraocular lenses

This thesis describes the outcome in visual acuity and refraction in patients with multifocal intraocular lens (IOL) implantation after previous myopic or hyperopic laser surgery and it describes the results of retreatments for residual refractive error after such procedures. Also it evaluates and compares various IOL power prediction formulas available on the American Society of Cataract and Refractive Surgery (ASCRS) post-refractive surgery IOL power calculator.
Multifocal IOL implantation in eyes after previous myopic or hyperopic laser surgery give good results with mean uncorrected distance visual acuity (UDVA) of 0.14 Logarithm of minimum angle of resolution (LogMAR) and 0.16 LogMAR respectively, and 57% and 63% of eyes within ± 0.50 Diopter (D) of emmetropia, respectively. Results were less predictable in eyes with myopia greater than 6.0 D. Residual refractive error in these eyes can be successfully treated. However, in 15% of patients repeated procedures were necessary to achieve a satisfactory result. Complications were seen in 10% of eyes and the results show that it seems safer to perform retreatment with surface ablation than with flap re-lifting.
The comparison of different IOL power calculation formulas for myopic eyes showed that the Shammas formula was least accurate in predicting IOL power. When no historical refractive data was available, the Barrett True-K No History formula performed best. In the hyperopic group all tested formulas performed equally except for the Modified Masket formula, which performed less accurately than the Masket formula, Barrett True-K formula and mean value of all formulas.