I read with interest the correspondence1,2 concerning Marchini et al.'s3 ultrasound biomicroscopic (UBM) observations of anterior movement of monofocal intraocular lenses (IOLs) during accommodation in pseudophakic eyes. Unfortunately, Marchini et al.3 did not incorporate unchanging positional references in the compared images to ensure image correspondence.4 Examination of the compared figures in Marchini et al.'s article reveals perspective distortion that precludes an objective measure of the change in position of the monofocal IOL during accommodation.
As noted in Figures 1 to 3, which are reproductions of Marchini et al.'s Figures 3 to 5, the center of the monofocal intraocular optic is thicker and/or its anterior curvature is flatter when the eye is accommodated. Since it is physically impossible for the central thickness of a monofocal IOL to increase or its anterior curvature to flatten as a consequence of accommodation, the imaging plane of the UBM was shifted between capture of the unaccommodated and accommodated images. This shift in the UBM axis can account for all of Marchini et al.'s observations. Thus, without proper image registration, there is no objective basis for Marchini et al.'s presumption that the monofocal IOL moved anteriorly during accommodation.
1. Osher RH., 2008. Initial report of IOL-induced accommodation [letter], J Cataract Refract Surg, 34, 2009.
2. Marchini G, Pedrotti E, Visentin S. Reply to letter by Osher RH, Initial report of IOL-induced accommodation. J Cataract Refract Surg. 2008;34:2009.
3. Marchini G, Pedrotti E, Modesti M, Visentin S, Tosi R. Anterior segment changes during accommodation in eyes with a monofocal intraocular lens: high-frequency ultrasound study. J Cataract Refract Surg. 2008;34:949-956.
4. Schachar RA, Kamangar F. Proper evaluation of accommodating IOLs. J Cataract Refract Surg. 2006;32:4-6.