Purpose: To test the reliability of a corneal radius correcting factor (R factor) in
calculating intraocular lens (IOL) power in eyes that developed cataract after
refractive surgery and compare it with the clinical history (CHM) and double-K (DKM)
methods.
Setting: Department of Ophthalmology, Second University of Naples, Naples, Italy.
Methods: Nineteen eyes from the literature that underwent cataract extraction and
IOL implantation after refractive surgery were used to compare actual postoperative
and expected refractive errors utilizing the R factor, CHM, and DKM. Intraocular lens
powers were calculated with 3 formulas: SRK/T, Hoffer Q and Holladay 1. The
differences were evaluated with the Wilcoxon test and Spearman correlation.
Results: With the R factor SRK/T and Holladay 1 formulas gave the best results;
16 (84.2%) and 17 (89.5%) eyes were within 62 diopters (D) of emmetropia. With
CHM, the best results were obtained using the SRK/T and Holladay 1 formulas; with
both formulas 12 (63.2%) eyes were within 62 D of emmetropia. With DKM, the best
results were obtained using SRK/T and Holladay 1 formulas; with both formulas
10 eyes (52.63%) were in the range of 62 D from emmetropia.
Conclusions: The R factor can be used with the SRK/T or Holladay 1 formula
because this method seems comparable or superior to DKM and CHM