AGREEMENT BETWEEN VAULT IN IMPLANTABLE COLLAMER LENS (ICL) USING ANTERIOR SEGMENT OPTICAL COHERENCE TOMOGRAPHY (AS-OCT) AND USING A SWEPT-SOURCE OPTICAL COHERENCE (SS-OCT) BIOMETER.

ICL are used as a refractive surgery technique in which the lens is implanted in the posterior chamber in front of the crystalline lens. The distance between the ICL and the crystalline lens, the vault, is a parameter relevant for predicting the interaction between the ICL and anatomical structures. AS-OCT is the most used method of vault monitoring. New SS-OCT biometers allow imaging the entire eye in a single B-scan with high precision. These characteristics potentiate the SS-OCT biometers as alternative imaging devices for vault monitoring. This study assessed the agreement between vault measurements using an AS-OCT and a SS-OCT biometer.  

Ophthalmology Clinic Vista Sánchez Trancón, Badajoz, Spain

Prospective case series measured the vault of 24 eyes implanted with spherical ICL (EVO-V4c, STAAR Surgical, USA) one-month postoperatively. Measurements were performed in random order using the AS-OCT Visante (Carl-Zeiss Meditec, Germany) and the SS-OCT biometer IOL-Master 700 (Carl-Zeiss Meditec, Germany), on the same day. For the AS-OCT Visante, vault measurements were performed using the software in-built callipers. For the IOL-Master 700 a custom written routine identified the edges of the ICL and crystalline lens in the B-scan images, the vault was then calculated as the difference between posterior ICL surface and anterior crystalline lens surface. Agreement between measurements was assessed through mean difference and limits of agreement calculated as the 95% confidence interval of the differences.

The IOL-Master 700 allowed the imaging and detection of the ICL contours in all eyes with greater detail than the AS-OCT Visante. For the AS-OCT Visante the mean vault was 557.0±279.3 µm and for the IOL-Master 700 was 536.7±263.0 µm. The mean difference was 20.3±39.7 µm (t-test, p=0.020) and the limits of agreement were -57.5, +98.1 µm. The vault measurements were highly correlated (R²=0.98, p<0.001). Using the IOL-Master, the intra-individual vault measurements performed in six meridians (0 to 150 degrees, 30 degrees steps), showed a mean coefficient of variation of 2.3% (range: 1.8 to 10.4%).  

The IOL-Master 700 allows a superior visualization of the ICL and faster imaging acquisition compared to the AS-OCT Visante. Both devices yielded proximal and highly correlated vaults, however the instruments should not be considered interchangeable as the IOL-Master 700 tends to measure smaller vaults. Differences between devices may be related to the instruments’ fixation targets lighting and individuals’ pupil dynamics. The IOL-Master 700 faster image acquisition of various ocular meridians may improve the precision in the ICL tilt and decentration assessment.