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D. Prescott, J. W. Cowden, V. Lopez; The Effect of Soft Contact Lenses on Biometry Prior to Cataract Surgery. Invest. Ophthalmol. Vis. Sci. 2010;51(13):5410.
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A case is presented of a 61 year old male who underwent cataract surgery after inadvertently undergoing biometric measurements while wearing soft contact lenses. His postoperative refraction was unacceptable and he underwent an intraocular lens exchange with good results. The current study looks at the effect of wearing soft contact lenses while undergoing measurements with the IOLMaster (Carl Zeiss Meditec, Inc., Dublin, CA). A pattern is sought that would easily alert the surgeon if this unfortunate mistake has been made.
Biometry was performed on 16 eyes from 8 healthy myopic volunteers. Each was measured while wearing their own soft contact lenses and again without the lenses. Axial length, keratometry readings, anterior chamber depths, and IOL power calculations for a plano postoperative refraction were recorded. A comparison between the two measurement groups was performed.
The refractions of the volunteers ranged between -0.25 and -8.125 spherical equivalent. Axial length (AL) and anterior chamber depth were minimally changed by the use of soft contact lenses. Average keratometry(CR) readings were changed by an average of 3.6 D. The average miscalculation in IOL power was 4.22 D. The value of miscalculation was very similar to the refraction of each subject. The average AL/CR ratio for the contact group was 3.18 while the average for the non-contact group was 2.92.
The wearing of soft contact lenses during biometric measurements will cause an error largely dependent on the change in corneal keratometry measurements. In myopic patients, it will cause the reading to be considerably flatter resulting in a miscalculation of intraocular lens power roughly equivalent to the power of the contact lenses. Outlying keratometry readings may indicate this error and deserve repeat measurement. A simple calculation of AL/CR will also help identify those that may have been measured with IOLMaster while wearing their soft contact lenses.
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