Purpose: To evaluate the percentage of eyes that could not be measured using optical biometry and ultrasound applanation and the reasons.
Setting: Department of Ophthalmology, Johannes Gutenberg-University Hospital, Mainz, Germany.
Methods: Optical biometry (IOLMaster, Carl Zeiss Meditec AG) and A-scan ultrasound biometry were performed consecutively in 253 eyes scheduled for cataract surgery the next day. Lens opacities were evaluated with the Opacity Lensmeter (Interzeag), and a slitlamp examination and measurement of visual acuity were performed. The 2 techniques were compared in terms of the rate of and reasons for primary measurement failure.
Results: Measurement with the IOLMaster was not possible in 44 eyes (17%). Failed measurements were the result of a combination of low visual acuity and lens opacity in 45% of eyes, posterior subcapsular opacity in 25%, and macular disease in 7%. Measurement with ultrasound biometry was not possible in 10 eyes (4%); 7 eyes were filled with silicone oil and in 3 cases, the patient refused biometry.
Conclusions: Optical biometry allowed comfortable, noncontact, high-precision measurement in the optical axis. Uncorrected visual acuity and lens opacity were predictors of successful measurements. Eyes with dense cataract or poor visual acuity are better evaluated using ultrasound applanation.