Factors associated with poor predictability by intraocular lens calculation formulas

S. C. Richards, R. J. Olson and W. L. Richards

In this study, we evaluated and compared two groups of posterior chamber intraocular lens (IOL) implantation cases. One group consisted of patients whose postoperative refraction was accurately predicted by IOL calculation formulas, while the other group included patients whose postoperative refraction was poorly predicted by the same formulas. We found that although postoperative astigmatism was greater in the poorly predicted group, preoperative to postoperative changes in astigmatism did not differ between the two groups. The poorly predicted group also had a shorter average axial length, a greater proportion of females, and an increased variability in most of the measurements we performed. The two groups did not differ significantly in terms of measured postoperative anterior chamber depth, age at the time of the surgery, IOL power and style implanted, complication rate, or preoperative corneal integrity.