INTRAOCULAR-LENS POWER CALCULATION USING INTRAOPERATIVE RETINOSCOPY

Background Preoperative biometry for calculation of the refractive pow er of intraocular lenses is not sufficiently reliable in certain cases . Most frequently inaccuracies tend to occur in highly myopic eyes. Pr eceding refractive procedures can also impair IOL-calculation or even make it impossible. Patients In a highly myopic patient IOL-power calc ulation was not possible with conventional calculation formulas due to a preexisting refractive silicone lens located between the cataractuo us natural lens and the iris. In another myopic patient ultrasound mea surement of axial eye length produced variable and unreliable results. Therefore retinoscopy was performed intraoperatively in the aphakic e ye. Refractive power of the IOL was calculated using a new formula. Fo r validation of the method retinoscopy was performed intraoperatively in a second group of 11 patients with unproblematic ultrasound biometr y. Results In 3 eyes IOL power was chosen according to intraoperative retinoscopy. A maximal deviation of 1.25 D from the aimed refraction r esulted. In the second group, the retinoscopic method produced partial ly considerably inaccurate results as compared to the ultrasound biome try. In accuracies increased with the extent of hyperopia. Conclusions In cases of difficult or inaccurate preoperative ultrasound biometry IOL power can be estimated after intraoperative retinoscopy in the aph acic highly myopic eye. IOL power can be calculated instantly using co mputer programs or tables. This method additionally enables the surgeo n to control the refractive result of intraocular lens implantation pr ior to wound closure. However this method lacks reliability in higher hyperopic eyes, as in these cases small changes in corneal vertex dist ance of the lens used for retinoscopy highly alter the result.