Anterior Segment Biometry during Accommodation Imaged with Ultralong Scan Depth Optical Coherence Tomography

Abstract

Purpose To measure by ultra-long 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 (D) were imaged in two repeated measurements at minimal and maximal accommodation. Methods A specially adapted 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 (COR) and the intraclass correlation coefficient (ICC) 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 CORs and ICCs for CCT, ACW, ACD, LT, LCP, and ASL were excellent (1.2% to 3.59% and 0.998 to 0.877, respectively). They were higher for PD (18.90% to 21.63% and 0.880 to 0.874, respectively), and moderate for LAC and LPC (34.86% to 42.72% and 0.669 to 0.251, respectively) in the two accommodative states. Compared to minimal accommodation, PD, ACD, LAC, LPC, and LCP decreased and LT and ASL increased significantly at maximal accommodation (P<0.05), while CCT and ACW did not change (P>0.05). Conclusions 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.

Static and dynamic crystalline lens accommodation evaluated using quantitative 3-D OCT

“…Optical Coherence Tomography (OCT) is a promising tool to image the anterior segment of the eye, due to its high-resolution, high-speed and non-contact nature [21][22][23][24][25] [38], and increased coherence length of swept sources [39,40]. Some of these techniques have been successfully used to quantify the 3-D geometry of the anterior segment of the eye [30,39].…”

“…Ortiz et al reported the first 3-D in vivo topography of the human crystalline lens [30]. Quantitative analysis (in most cases limited to axial biometry) has also been reported from 2-D cross-sections of the anterior segment of the accommodating human eye in vivo [19,[36][37][38].…”

Changes in anterior chamber eye during accommodation as assessed using a Dual Scheimpflug system

“…Using ultralong scan depth optical coherence tomography, Du et al (7) measured dimensional changes in the anterior segment of human eyes during accommodation. The relative change in the pupil diameter with a maximum accommodation effort of -5 D was 21.74%.…”

“…Table 1 is a compilation of the results of all studies that evaluated at least one of these three eye metrics during accommodation. Studies assessing the changes in central ACD , mean ACA (16) , and PD (3,7,26,28,29) during accommodation concluded that these metrics decreased after increasing the stimulus vergence. Figure 1 The changes in the peripheral ACD and ACA at different meridians during accommodation have not been studied.…”

“…Such studies will enable the development of new anterior chamber IOLs that better fits the anterior chamber eye. Several studies have evaluated the changes in pupil diameter during accommodation (3,7,26,28,29) . However, four of these studies (3,7,26,28) included myopic or hyperopic subjects and mea-sured the changes in pupil diameter with stimuli vergences beyond 5 D. Further, a Scheimpflug system has not been used to study the changes in pupil that occur during accommodation.…”