Capsular Tension Ring Implantation for Intraocular Lens Power Calculation in Highly Myopic Eyes: Secondary Analysis of a Randomized Clinical Trial

Importance Capsular tension ring (CTR) implantation has been shown to reduce intraocular lens (IOL) decentration and tilt in high myopia. However, the effect of CTR implantation in highly myopic eyes on IOL power calculation remains unclear, particularly in new-generation formulas. Objective To evaluate the influence of CTR implantation on IOL power calculation in highly myopic eyes. Design, Setting, and Participants This is a prespecified secondary analysis of outcomes of a randomized clinical trial conducted between November 2021 and September 2023 at the Zhongshan Ophthalmic Center in Guangzhou, China. Cataract patients with an axial length (AL) of 26 mm or longer were enrolled and stratified into 3 strata based on AL (stratum 1: AL 26-<28 mm; stratum 2: AL 28-<30 mm; stratum 3: AL >= 30 mm). Interventions Participants were stratified based on AL and randomized to the CTR group (a C-loop IOL combined with a CTR) or the control group (only a C-loop IOL) within each stratum. Main Outcomes and Measures Predictive outcomes of 6 new-generation formulas and 4 traditional formulas were evaluated. The arithmetic and absolute prediction error (PE) and the percentages of eyes within +/- 0.25 diopter (D), +/- 0.50 D, +/- 0.75 D, and +/- 1.00 D of PE were analyzed. Results A total of 186 eyes of 186 participants were randomized into the CTR group (93 eyes [50%]) or control group (93 eyes [50%]). Excluding a withdrawal case and 24 eyes with best-corrected visual acuity less than 20/40, 80 eyes in the CTR group (86.0%) and 81 eyes in the control group (87.1%) were analyzed. Of 161 participants analyzed, overall mean (SD) participant age was 56.7 (10.5) years, and 100 participants (62.1%) were female. No differences were observed in arithmetic PE between the CTR and control groups in any strata. The CTR group showed smaller absolute PE in all new-generation formulas and higher percentage of PE within +/- 0.50 D in the Emmetropia Verifying Optical 2.0, Hoffer QST, LISA, and Pearl-DGS formulas only for eyes with an AL of 30 mm or longer compared with the control group. In traditional formulas, no differences were observed between the 2 groups in any strata. Conclusions and Relevance In this secondary analysis, CTR implantation in highly myopic eyes did not affect the target refraction and can improve the prediction accuracy of new-generation IOL calculation formulas in eyes with AL of 30 mm or longer. These findings support use of CTR implantation in eyes with an AL of 30 mm or longer.