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Ashraf Mahmoud, Li Wang, Cynthia Roberts, David Castellano, Mitchell Weikert, Douglas Koch; Predicting IOL Position from Pre-op A-scan Data. Invest. Ophthalmol. Vis. Sci. 2013;54(15):814.
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The purpose of this study is to determine if there is a “signature” feature in the pre-op A-scan of the Lenstar (Haag-Streit, Switzerland) that can help predict the location of the implanted intraocular lens (IOL) after cataract surgery.
Lenstar measurements were acquired from 51 eyes of 47 subjects pre- and post-cataract surgery. Cataract surgeries were performed by 3 surgeons from the Department of Ophthalmology, Baylor College of Medicine, Houston, TX and 1 surgeon from the Department of Ophthalmology, The Ohio State University, Columbus, OH. Post-op measurements were used to determine the actual position of the implanted IOL. Pre-op measurements were reprocessed to extract a signature feature that was used to predict the post-op position. The differences, predicted minus actual, were calculated.
The mean difference between predicted and actual IOL position is -0.34 mm ±0.20mm, range: 0.06 mm to -0.78 mm. The adjusted range based on the mean difference is 0.4 mm to -0.44 mm. For an example eye with Total Corneal Power of 40 D, IOL of 20 D, and a lens position of 4 mm, the Total Power of the Eye (TPE) is 54.72 D. If the lens position is 3.6 mm then the TPE is 55.19 D. If the lens position is 4.44 then the TPE is 54.22 D. The largest dioptric error over the predicted minus actual range is ~0.5 D.
A signature feature of a pre-op Lenstar measurement may be useful for predicting post-op IOL position or “effective lens position” in IOL power calculation formulas, independent of surgeon factors, lens constants, or prior refractive surgery.
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