Optical Biometry Errors in Eyes with Iris-Claw Phakic Intraocular Lenses

To evaluate the effect of iris-claw phakic intraocular lenses (pIOLs) on anterior chamber depth (ACD) measurement by optical biometers and the potential impact of ACD errors on hypothetical intraocular lens (IOL) power selection for cataract surgery.

Seventy-six eyes of 38 patients with iris-claw pIOLs (Artiflex) underwent biometry using Pentacam (Scheimpflug), Lenstar LS-900 (optical low-coherence reflectometry), and Eyestar 900 (swept-source OCT). The failure and misidentification rates of ACD measurement were recorded. Eyestar B-scans were manually reviewed and corrected when segmentation errors were identified. Hypothetical IOL power was calculated using Barrett Universal II and SRK/T formulas.

Pentacam successfully measured ACD in all 76 eyes. Lenstar LS-900 angd Eyestar 900 failed to provide ACD measurements in 4 eyes (5.3%) and 14 eyes (18.4%), respectively. Using a predefined threshold of >10% deviation from the Pentacam value, inaccurate ACD measurements were identified in 30 eyes (39.5%) with Lenstar and in 17 eyes (22.4%) with Eyestar. On Eyestar, 20 eyes (26.3%) showed misidentification of the anterior pIOL surface as the anterior capsule of the crystalline lens, and 11 eyes (14.5%) were interpreted as aphakic. After manual correction, Eyestar ACD values closely matched Pentacam measurements, with a mean difference of 0.04 ± 0.03 mm. Correction of erroneous ACD measurements changed Barrett Universal II-based hypothetical IOL power selection by at least 0.50 D in 7 of 17 affected eyes (41.2%).

In eyes with iris-claw pIOLs, automated optical biometers may misidentify ocular structures and underestimate ACD, potentially leading to clinically meaningful differences in hypothetical IOL power selection. Manual review and correction of Eyestar B-scan images restored ACD measurements to close agreement with Pentacam values. These findings highlight the importance of careful inspection of raw biometry images in such eyes, particularly when using formulas that incorporate measured ACD.