Researchers identified a theoretical limit for intraocular lens (IOL) calculation in 91.9% of eyes between -0.50 D and +0.50 D and identified several biometric sources of error, according to a study reported in Archivos de la Sociedad Española de Oftalmología. 

The team conducted a review to determine the mean values for several ocular parameters contributing to error in IOL implantation. They calculated the change in refraction in the spectacle plane caused by a variation of 1 standard deviation (SD) and left  the other variables unchanged. They used the Barrett Universal-II formula to determine axial length, keratometry, anterior chamber depth, lens thickness and central corneal thickness as input variables for calculating the intraocular lens. 

Investigators reported the primary source of error was intraoperative and post- operative variability not considered by formulas (49.32%). They also identified postoperative subjective refraction, mean keratometry, and variability in labeling IOL power as factors contributing to error (38.29%, 5.98%, and 5.09%, respectively). Axial length, mean corneal radius of curvature, anterior chamber depth, lens thickness and white-white also contributed to error (<1% for all). 


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“To minimize random errors, the use of optical biometry and state-of-the-art formulas for intraocular lens calculation is essential,” according to the researchers. “In the future, the use of more accurately labeled lenses and the development of new formulae in intraocular lens calculation may increase the accuracy limit obtained in this study.”

Study limitations include potential errors in effective lens position prediction.

Reference

Romero Valero D, Escolano Serrano J, Monera Lucas CE, Castilla Martínez G, Martínez Toldos JJ. Limits of the precision in refractive results after cataract surgery. Arch Soc Esp Oftalmol. Published online May 24, 2022. doi:10.1016/j.oftal.2021.11.002