Purpose To quantitate lens nuclear opacity using long-range swept-source optical coherence tomography (SS-OCT) images and to evaluate the correlation of this method to Lens Opacities Classification System III (LOCS III) and a Scheimpflug imaging-based grading system (Pentacam Nuclear Stage function; PNS).

Methods This study enrolled 120 participants (120 eyes) with age-related nuclear cataracts. The best-corrected visual acuity (BCVA), LOCS III nuclear opalescence (NO) and nuclear colour (NC) were obtained. The nuclear density measured using PNS function (ND_PNS) was recorded. Three successive series of long-range SS-OCT images were captured, and the nuclear region was analysed using ImageJ (NIH, Bethesda, Maryland, USA) to generate SS-OCT image-based nuclear density (ND_SS-OCT). The repeatability of ND_SS-OCT measurement was evaluated using within-subject coefficient of variation (CV_w) and intraclass correlation coefficient (ICC). Correlations of ND_SS-OCT with NO and NC, BCVA and ND_PNS were analysed. According to the integrity of nucleus imaged by Pentacam, patients were divided into two groups, and the parameters were compared between groups.

Results The CV_w and ICC for ND_SS-OCT measurement were 1.5 % and 0.994, respectively. The ND_SS-OCT significantly correlated with NO (r=0.831), NC (r=0.873), BCVA (r=0.655) and ND_PNS (r=0.891). The ND_SS-OCT, NO and NC, and BCVA were significantly different between the two groups.

Conclusion Lens nuclear opacity quantitation using long-range SS-OCT images was repeatable and correlated well with LOCS III and PNS function. The Scheimpflug principle had a limitation in imaging dense nucleus. Long-range SS-OCT seems more promising for objectively and quantitatively assessing lens nuclear opacity.