Lens rotation and spherocylindrical over-refraction as predictors for soft toric lens evaluation

Prospective data from 72 patients (128 eyes) fitted with one type of soft toric lens of the double slab-off design were analyzed for lens rotation and spherocylindrical over-refraction (SCO) for the purpose of assessing their accuracy as predictors in soft toric evaluation. Initial trial lens data were compared with final lenses and best spectacle refraction. The mean difference in lens rotation between the initial and final lens visits was 9.9 degrees (SD = 11.5 degrees), and the mean difference between the actual refractive astigmatism and the expected astigmatism, calculated from ophthalmic cross-cylinder equations, was 0.22 D (SD = 0.12 D). Considerable variability existed in lens rotation in the various ametropias during the course of several assessments; SCO provides the best evidence of the fit of toric soft lenses. The implications for other lens types are discussed.