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N. M. Shoshani, G. T. Liu, A. Shrivastava; Reliability and Reproducibility of IOLMaster Optical Biometry Measurements for Cataract Surgery Preoperative Assessment, Pre- and Post-Dilation and Examination. Invest. Ophthalmol. Vis. Sci. 2010;51(13):5409.
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Studies have shown that dilation and examination of the eye can result in differences in biometry, leading to the belief that precise preoperative measurements should be based on a pre-examined eye. Thus, a return visit is necessary to complete the preoperative assessment. We evaluate the effects of pupillary dilation, applanation tonometry, and slit-lamp examination on IOLMaster (Zeiss) biometry, axial length, anterior chamber depth, and corneal K values, with additional evaluation of test-retest variability. The goal is to identify whether optical biometry can be performed on the initial cataract evaluation visit, and reduce the need for an additional visit for biometry.
80 phakic eyes from 47 patients ages 60 and above presenting to outpatient ophthalmology clinic were recruited. All patients had IOLMaster biometry performed by the same operator before and after dilation, applanation tonometry, and full slit-lamp exam. From within this group, a control group of 30 eyes from 17 patients underwent an additional set of pre-examination IOLMaster measurements. SRK/T formula was used to calculate IOL power and refractive error for MTA4UO and ALCON ACRYSOF lenses. Refractive errors in the post-examined eye were also calculated by matching post-examined plano IOL power to the pre-examined eye refractive error data, to assess refraction when using the IOL power attained post-dilation and examination.
The IOLMaster showed a high level of reproducibility between pre-examination and control groups as well as between pre- and post-examination groups. Mean refractive error in the examined group was .2 for the MTA4UO lens compared to an unexamined group mean refraction of .1 (p=.0002) and control of .13. For MTA4UO, the mean difference in refractive error between unexamined and examined groups was .21, compared to .15 between unexamined and control groups. Similar results were obtained for ALCON ACRYSOF. Differences in axial length, anterior chamber depth, K1 and K2 were negligible in all three groups.
We conclude that the difference in biometry and refractive error post-examination is minimal, and that IOLMaster measurements may be taken post-examination. This will enable clinicians and patients to minimize redundant visits by performing pre-operative biometry measurements on the initial cataract assessment visit.
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