Prospective evaluation of a regression-determined formula for use in triple procedure surgery

A surgeon-specific regression equation was applied prospectively to determine the intraocular lens (IOL) power for use in 52 consecutive patients undergoing triple procedure surgery. At their final refraction, 85% (44/52) of these patients could see 20/40 or better. Upon comparing the preoperatively determined refractive goal with that actually obtained, an "ideal" IOL power which would have resulted in the refractive goal was determined. The IOL power selected by the regression formula was within 2 diopters (D) of the ideal IOL power in 67% (35/52) of the cases. For comparison, the power which would have been selected if the Sanders-Retzlaff-Kraff (SRK) or Binkhorst formula was used would have been within 2 D of the ideal IOL power in 62% (SRK, 32/52) and 58% (Binkhorst, 30/52) of the cases. Deviations from the ideal IOL power were predominantly in the undercorrected category for all three formulas evaluated. The authors conclude that even though a surgeon-specific regression formula relying on preoperative axial length performed fully as well as either the SRK or Binkhorst formulas, the choice of which formula to apply remains in the surgeon's hands.