Anterior segment biometry during accommodation imaged with ultralong scan depth optical coherence tomography

Purpose: To measure by ultralong scan depth optical coherence tomography (UL-OCT) dimensional changes in the anterior segment of human eyes during accommodation. Design: Evaluation of diagnostic test or technology. Participants: Forty-one right eyes of healthy subjects with a mean age of 34 years (range, 22-41 years) and a mean refraction of -2.5±2.6 diopters were imaged in 2 repeated measurements at minimal and maximal accommodations. Methods: A specially adapted and designed UL-OCT instrument was used to image from the front surface of the cornea to the back surface of the crystalline lens. Custom software corrected the optical distortion of the images and yielded the biometric measurements. The coefficient of repeatability and the intraclass correlation coefficient were calculated to evaluate the repeatability and reliability. Main Outcome Measures: Anterior segment parameters and associated repeatability and reliability upon accommodation. The dimensional results included central corneal thickness (CCT), anterior chamber depth and width (ACD, ACW), pupil diameter (PD), lens thickness (LT), anterior segment length (ASL = ACD + LT), lens central position (LCP = ACD + 1/2LT), and horizontal radii of the lens anterior and posterior surface curvatures (LAC, LPC). Results: Repeated measurements of each variable within each accommodative state did not differ significantly (P>0.05). The coefficients of repeatability (CORs) and intraclass correlation coefficients for CCT, ACW, ACD, LT, LCP, and ASL were excellent (1.2%- 3.59% and 0.998-0.877, respectively). They were higher for PD (18.90%-21.63% and 0.880-0.874, respectively) and moderate for LAC and LPC (34.86%-42.72% and 0.669-0.251, respectively) in the 2 accommodative states. Compared with minimal accommodation, PD, ACD, LAC, LPC, and LCP decreased and LT and ASL increased significantly at maximal accommodation (P<0.05), whereas CCT and ACW did not change (P>0.05). Conclusions: The UL-OCT measured changes in anterior segment dimensions during accommodation with good repeatability and reliability. During accommodation, the back surface of the lens became steeper as the lens moved forward. Financial Disclosure(s): The authors have no proprietary or commercial interest in any of the materials discussed in this article.