Authors: Carter W. Lim, Sohel Somani, Hannah Chiu, Raj Maini, Eric S. Tam

Purpose: To assess the corneal changes following intrastromal limbal relaxing incisions (LRIs) of varying arc lengths made during femtosecond laser assisted cataract surgery (FLACS) using the Catalys platform. 

Study Design: Retrospective cohort study 

Methods: FLACS with intrastromal LRI were performed by 4 surgeons between June-September 2018 using standardized settings on the Catalys platform. The intrastromal LRI was created 8.5 mm from the cornea centre, 60% stromal depth at steep axis. Single LRI arc lengths of 30°, 40°, 50°, or 60° were applied based on incremental preoperative corneal astigmatism of 0.1D or greater. Keratometric astigmatism and axes were calculated preoperatively (preop), postoperatively at 1-week (POW1) and 1-month (POM1). Vector analyses were performed using the Alpins vector method with ASSORT software. 

Results: For 30° (n=125 eyes), 40° (n=69 eyes), 50° (n=8 eyes), and 60° (n=13 eyes) LRIs, mean preop astigmatism±SD were 0.70±0.37D, 0.91±0.37D, 1.25±0.60D, and 1.65±0.73D, respectively. 30° arcs had significantly increased mean astigmatism±SD at POW1 (0.94±0.61D) and POM1 (0.76±0.46D) relative to preop mean (P<0.0001). While there were trends toward reduced corneal astigmatism with 40°, 50° and 60° LRIs at POW1 and POM1, the difference from preop means were not significantly different. POM1 vector analyses of 30°, 40°, 50°, 60° groups showed correction indices of 4.77, 0.5, 0.31, 0.99; mean flattening effects of 0.13D, 0.06D, 0.16D, 2.13D; mean angle of errors of 41°, -43°, 36°, 0°, respectively. 

Conclusions: 30° LRIs did not predictably impact preop astigmatism. While there were trends toward reduced corneal astigmatism at 40° and 50° LRIs, larger intrastromal LRIs (60°) led to more predictable astigmatic change with greater flattening effect and lower angle of error.