CORRECTION OF LOW AND HIGH ASTIGMATISM WITH POSTERIOR CHAMBER COLLAMER PHAKIC INTRAOCULAR LENS - A COMPARATIVE STUDY

To compare the visual, refractive and safety results of posterior chamber collamer phakic intraocular lens (ICL V4C and V5) implantation for the correction of low and high astigmatic refractive errors.

Department of ophthalmology, Hospital de Braga, Portugal.

This retrospective study included 205 eyes submitted to refractive surgery with implantation of posterior chamber collamer phakic intraocular lens (ICL V4C and V5) in Hospital de Braga from 2014 to 2019. Two groups were created according to pre-operative manifest cylinder - low astigmatism (group 1) for those with < 2.5D, which included 97 eyes, and high astigmatism (group 2) for those with ≥ 2.5D, composed of 108 eyes. The two groups were compared regarding efficacy, safety and predictability at 12 months postoperatively. Astigmatic refractive correction was evaluated using Alpins’s vectorial analysis.

Mean preoperative manifest cylinder was -1.85 ± 0.27 in group 1 and -3.52 ± 0.95 in group 2. Best corrected visual acuity (BCVA) was 0.10 ± 0.10 and 0.13 ± 0.11 logMAR (p=0.02), respectively. At 12 months of follow-up, the uncorrected visual acuity (UVA) was 0.05 ± 0.10 in group 1 and 0.08 ± 0.12 logMAR in group 2, with no statistical differences between groups (p=0.15). The achieved safety indexes were 1.25 ±0.30 and 1.30 ± 0.29 (p=0.07), respectively. The efficacy indexes were 1.15 ± 0.28 and 1.16 ± 0.26 (p=0.58). The postoperative spherical equivalent was 0.19 ± 0.42 in group 1 and -0.28 ± 0.51 in group 2 (p=0.01). In about 71.1% of cases the manifest cylinder obtained was <0.50D (91.7% achieved <1.00D) in group 1 and 57.5% of cases in group 2 attained <0.50D (81% achieved <1.00D) (p=0.04). The astigmatic vectorial analysis revealed a correction index of 0.91 ± 0.46 in group 1 and 0.89 ± 0.17 in group 2 (p=0.81). The index of success was 0.54 ± 0.45 and 0.29 ± 0.16, respectively (p<0.01). The surgical induced astigmatism was 1.37D ± 0.66 and 2.69D ± 1.00 (p<0.01). The average loss of endothelial cells was 0.85% in group 1 and 1.31% in group 2 (p=0.57). In 2 patients of group 1 and 4 patients of group 2 it was necessary to reposition the lens due to significant postoperative misalignment. No vision threatening conditions were reported.

Correction of astigmatic refractive error with posterior chamber collamer phakic intraocular lens implantation provides good refractive and visual results regardless of the preoperative magnitude of astigmatism, with an excellent safety profile. Using Alpins’s vectorial analysis we found a more effective cylinder correction in group 2.