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Mengchan Sun, Pablo Pérez-Merino, Sonia Durán, Ignacio Jiménez-Alfaro, Susana Marcos, Visual Optics and Biophotonics Lab; OCT-based ray tracing on pseudophakic eyes to identify optimal IOL centration. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):2972.
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© ARVO (1962-2015); The Authors (2016-present)
Quantitative 3D anterior segment Optical Coherence Tomography (OCT) provides full anatomical information to build customized eye models to identify the IOL centration that would produce best optical quality.
4 subjects implanted with monofocal aspheric IOLs (Bausch and Lomb, US; Alcon, US) were measured 90 days after cataract surgery. 3-D quantitative anterior segment geometry (corneal topography; anterior chamber depth; IOL tilt & decentration; foveal position) was measured using a custom-developed spectral OCT 840nm; acquisition rate=25,000 A-Scans∕s; acquisition time =0.72 s; 7(vertical)x15(horizontal)x7mm(axial). Total wave aberrations were measured using custom-developed Laser Ray Tracing at 785nm laser beam sampled 35 positions of a 4-mm pupil. The IOL geometry was characterized ex vivo using profilometry. OCT images were processed and data were exported to ZEMAX to build full OCT-based customized computer eye models. Optical quality was calculated from measured/simulated wave aberrations in terms of Visual Strehl Ratio (VSR), for 4-mm pupils, and estimated for the native tilt & decentration, and simulated decentrations ranging from -2 to +2 mm in 0.1 mm steps in horizontal and vertical meridians, referred to the pupil center.
There was a good correspondence between measured and estimated wave aberrations using measured IOL tilt (VSR of 0.3 and 0.2, respectively). VSR varied across IOL decentrations, with a highest mean value of 0.4±0.2. The IOL vertical centrations producing optimal quality were decentered nasally in all cases, ranging from 0.1-1mm. Optimal vertical centration ranged from 0.4-1 mm inferiorly. These positions differed by -0.3 mm horizontally and 0.1 mm vertically on average from native IOL decentration values. Centering the IOL in the estimated optimal location produced an average improvement of 0.08 in VSR with respect to native decentration values and an average improvement of 0.13 in VSR with respect to zero decentration.
OCT-based customized eye models predict well optical quality in pseudophakic eyes implanted with state-of-the-art monofocal IOLs. Zero IOL decentration does not produce optical quality. The best IOL decentration can be obtained for each patient based on personalized models, and the achieved improvement may be of clinical relevance.
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