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From the G.B. Bietti Eye Foundation-IRCCS, Rome, Italy (GS, MC); and Jules Stein Eye Institute, University of California, Los Angeles, and St. Mary's Eye Center, Santa Monica, California (KJH).
The authors have no financial or proprietary interest in the materials presented herein.
The position of the intraocular lens (IOL) relative to the central anterior corneal apex is a major factor affecting the refractive outcome of cataract surgery, especially in short eyes requiring high power IOLs.1,2 When IOL power is calculated, this position has to be predicted by both theoretical thin lens formulas and thick lens methods such as ray tracing.3-9
Clinically, there is little need to routinely measure the IOL position postoperatively. However, this measurement can become important in several situations: (1) when a new method to predict the IOL position has to be validated in a sample of patients who had surgery, (2) when the behavior of an IOL in the bag is being assessed (eg, three-piece vs one-piece IOLs), (3) when the efficacy of accommodating IOLs has to be confirmed by evaluating the forward movement of their anterior surface, and (4) when the refractive outcome is different than expected and the surgeon needs to rule out a malpositioned IOL as the cause of the refractive error.
Postoperative measurements of the IOL position can be performed by several technologies. The first instruments to become available were optical pachymeters attached to Haag-Streit and Zeiss slit-lamps. These were used by Binkhorst in the 1970s to measure the movement of iris clip IOLs from the prone to supine position and later in the 1980s by Hoffer to establish the anatomical relationship between axial length and the postoperative IOL position.10-12 Ultrasound (US) biometry was used later and has consequently been regarded by some as the benchmark for comparison.9,13-17 More recently, several optical methods have been re-introduced: optical pachymetry,16,18 Scheimpflug imaging,16,17,19-21 scanning-slit topography,16 partial coherence interferometry,22-24 and optical coherence tomography.24-26 Among these technologies, Scheimpflug imaging has gained wide popularity due to the large variety of anterior segment measurements it can provide and constant advances in software and high measurement repeatability.27 We have previously shown that Scheimpflug measurements, as provided by a single rotating Scheimpflug camera (Pentacam; Oculus Optikgerate GmbH, Wetzlar, Germany), can be considered interchangeable with those provided...