Vol: 45 Issue: 6 month: June
ABERROMETRY IN SHORT EYES
Eyes with short axial lengths (ALs) tend to have less accurate refractive outcomes with cataract surgery than those with normal or long ALs. To determine which, if any, preoperative biometry-based formulas might work best in short eyes, researchers conducted a retrospective study of 51 eyes in 38 patients. The predicted residual refractive error was calculated preoperatively using Hoffer Q, Holladay 2, Haigis, Barrett Universal II and Hill-RBF formulas as well as using intraoperative aberrometry. Overall, intraoperative aberrometry was not significantly different from the best preoperative biometry-based methods for IOL power selection in short eyes. In particular, when intraoperative aberrometry disagreed with the preoperative prediction by more than 0.5D, the ability of intraoperative aberrometry to suggest a more emmetropic outcome was no better than chance.
S. Sudhakar et al., “Intraoperative aberrometry versus preoperative biometry for intraocular lens power selection in short eyes”, Vol. 45, #6, 719-724.
ABERROMETRY IN HIGH MYOPES
A prospective study of 79 eyes of 79 patients compared the accuracy of the Barrett Universal II, Haigis and Olsen formulas in calculating intraocular lens power in eyes with extreme myopia. In eyes with an axial length of 28.0-to-30.0mm, all three formulas were accurate. In eyes with axial lengths of 30.0mm or more, the Barrett Universal II formula was better than the Haigis formula. The accuracy of the Haigis formula in myopic eyes was affected by the axial length and keratometry value, whereas the accuracy of the Barrett Universal II and Olsen formulas was affected by axial length only.
X. Rong et al., “Intraocular lens power calculation in eyes with extreme myopia: Comparison of Barrett Universal II, Haigis, and Olsen formulas”, Vol. 45, #6, 732-737.
RAY TRACING AND ABERROMETRY
Investigators evaluated the accuracy of a new ray-tracing-based IOL power calculation method in a theoretical prospective study. The refractive spherical equivalent absolute error of the ray-tracing IOL power calculation method, based on individualised eye model data, a physical lens position predictor, retinal image quality metrics criteria for IOL power selection and exact IOL design information was calculated and compared with outcomes using the Barrett Universal II, Hill-RBF, SRK/T and Haigis formulas. There was no significant difference in absolute error between ray tracing and the Barrett Universal II or Hill-RBF. However, the absolute error was significantly lower compared with the Haigis and SRK/T formulas. The possibility to visualise the expected visual performance might facilitate IOL selection, the researchers note.
N. Hirnschall et al., “Pilot evaluation of refractive prediction errors associated with a new method for ray-tracing–based intraocular lens power calculation”, Vol. 45, #6, 738-744.