Reliability of a new correcting factor in calculating intraocular lens power after refractive corneal surgery.
OBJECTIVE
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.


METHODS
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 +/-2 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 +/-2 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 +/-2 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.
Department of Ophthalmology, Second University of Naples, 80100 Naples, Italy. nicola.rosa@unina2.it
Nicola
N
Rosa
Luigi
L
Capasso
Michele
M
Lanza
Gennarfrancesco
G
Iaccarino
Antonio
A
Romano
D002387:Cataract Extraction; D003315:Cornea / Q000601:surgery*; D019781:Corneal Topography; D006801:Humans; D020731:Keratomileusis, Laser In Situ; D054018:Lasers, Excimer; D007910:Lenses, Intraocular; D008962:Models, Theoretical; D055095:Optics and Photonics; D018903:Photorefractive Keratectomy; D011184:Postoperative Period; D054140:Refractive Surgical Procedures; D012044:Regression Analysis; D015203:Reproducibility of Results