Visual Acuity Improvement in Low, Moderate and High Myopia After Posterior-Chamber Phakic Implantable Collamer Lens Surgery in a Large Patient Cohort

Purpose: To compare best-corrected visual acuity (BCVA) before and after implantable collamer lens (ICL) surgery in patients with low, moderate and high myopia.Methods: A single-centre, prospective, registry-based study involving patients with myopia who received ICLs between October 2018 and August 2020. The study population was divided into three groups of subjects with low (from 0 to -6 D), moderate (-6 to -10 D) and high myopia (more than -10 D). We analysed uncorrected visual acuity (UCVA), best-corrected visual acuity (BCVA), spherical equivalent (SE), differences between BCVA pre- and 1-month postoperative, and line gain in BCVA 1 month after surgery.Results: A total of 770 eyes belonging to 473 patients were surgically intervened during the study period, of which 692 eyes completed 1 month of postoperative follow-up and were included in the study population. At 1-month follow-up, 478 eyes (69%) achieved a BCVA of 20/20, 599 (87%) obtained 20/25 or better, and 663 (96%) had a BCVA of 20/40 or better. We identified a significant improvement in BCVA (baseline 0.15 +/- 0.2 logMAR vs follow-up 0.07 +/- 0.2 logMAR, p<0.0001) and a significant reduction in SE (baseline -9.23 +/- 4.1 D, vs follow-up -0.21 +/- 0.8 D, p<0.0001), with a significant relationship between preoperative SE and line gain (r = -0.46, p<0.0001). We identified a significantly higher line gain among eyes with higher degrees of myopia (low myopia 0.22 +/- 0.69 lines compared to moderate myopia 0.56 +/- 1.1 lines and high myopia 1.51 +/- 1.9 lines, p<0.0001). Notably, 99.6% of eyes with a high grade of myopia achieved improvement to a low degree (less than -6 D) at follow-up. The safety and efficacy indexes were 0.083 +/- 0.1 and -0.001 +/- 0.1, respectively.Conclusion: In this large patient cohort, ICL surgery was related to a significant line gain in BCVA, particularly among eyes with higher degrees of myopia.