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Eduardo Martinez-Enriquez, Pablo Perez-Merino, Mengchan Sun, Sonia Durán-Poveda, Ignacio Jiménez-Alfaro, Susana Marcos; Full shape crystalline lens quantification from 3-D OCT images and its application to predict the post-operative IOL position.. Invest. Ophthalmol. Vis. Sci. 2017;58(8):1803.
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© ARVO (1962-2015); The Authors (2016-present)
Full shape crystalline lens quantification is critical to improve state-of-the-art intraocular lens (IOL) selection in cataract surgery. We estimated lens volume (VOL), surface area (SA), diameter (DIA) and equatorial plane position (EPP) in patients before cataract surgery, and we evaluated the EPP as an estimator of post-operative IOL position (ELP).
The anterior segment of 7 eyes (76±8 y.o, range, 66-87 y.o) from 6 patients before cataract surgery and 1 eye (80 y.o) post-operatively (Aspheric monofocal Asphina IOL, Zeiss) were imaged and quantified using a custom-developed 3-D Optical Coherence Tomography (OCT) system provided with distortion correction algorithms. Whole crystalline lens 3-D models were constructed from the information visible through the pupil (Martinez-Enriquez et al. IOVS 2016), and VOL, SA, DIA, lens thickness (LT) and EPP (distance from the anterior lens apex to the equatorial plane) were estimated pre-operatively. EPP was used as estimator of ELP. The estimation error was compared with state-of-the-art methods, namely: ELP=LT/2; Rosen et al. (2006) constant: ELP=0.41LT; and the intersection approach, where the ELP is estimated as the plane of intersection between anterior and posterior lens best fitting conicoid surfaces.
Mean VOL, SA, DIA, LT and EPP across subjects (±SD) was 208±27 mm3, 186±14 mm2, 9.27±0.32 mm, 4.76±0.42 mm & 2.16±0.22 mm, respectively. The ratio EPP/LT was patient-dependent (0.44-0.47) indicating the importance of individual anatomical measurements for ELP proper estimation. The ELP estimation error was 62 µm (equivalent to -0.07 D) using the newly proposed metric EPP, whereas using other metrics was: +202 µm (-0.27 D) using LT/2, -204 µm (+0.29 D) using Rosen constant, and -168 µm (+0.24D) using the intersection approach.
3-D OCT measurements with dedicated algorithms allow full quantification of the crystalline lens in-vivo. The estimated parameters (EPP in particular) provide valuable information for improving the estimation of the post-operative IOL position and thus the IOL selection. Improvements by 0.25 D in IOL power calculations resulting from accurate ELP accumulate to those arising from patient-specific measurements of posterior corneal surface, 3-D biometry and 3-D ray tracing analysis.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
Anterior segment 3-D model and post-operative IOL superimposed.
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