Fig. 2 Centration points visualization with the surgical microscope (A) and with LDV Z8 femto machine after docking (B)
a: CSFCLR marked with ink (blue arrow) on the cornea surface (the left coaxial smaller light). b: LDV Z8’s display of a pupil centered capsulotomy preset (blue arrow signalizing the CSFCLR, here presented with an enlarged ink mark).
CSFCLR -= coaxially sighted subject-fixated corneal light reflex
After implantation, the IOL was positioned in the capsular bag with its innermost diffractive ring in alignment with the first (CSFCLR) and fourth Purkinje reflex, while the patient was asked to fixate on the coaxial light of the surgical microscope; after pressing the optic against the posterior capsule, the chamber was sealed with the IOL optic seated against the capsular bag.
Statistical Analysis
Comparisons were based on paired and unpaired Student t-test, or non-parametric analysis tests when the equality of variances was not observed. Correlations were assessed using Pearson’s correlation test, and the results were confirmed with a non-parametric test (Spearman correlation test). All statistical tests were done using a significance level of α = 0.05.
The distance between the postoperative FPR and the IOL center, was designated as the primary outcome, with internal aberrometry, UDVA, UIVA and UNVA and patient-reported quality of vision selected as secondary outcomes.
The sample size was determined a piori using G*Power, for a difference test between two dependent means, using a significance level of α=0.05, a power of 90%, and a medium to large, expected effect size. The minimum number of subjects needed was 27. The statistical analysis was performed using R (v. 4.3.0) in RStudio (v. 2023.03.1+446).
RESULTS
Preoperative Patient Data
Thirty-two patients had both eyes operated, achieving a total of 64 eyes operated. Two of them were withdrawn from the study, as they did not complete the 3 years follow up.
The study population included 19 (63.3%) female and 11 (36.7%) male patients, with a mean age of 71±7 years old (range 59 to 87). The mean IOL power was +24.12±4.05 D (range 13.0 to 29 D). Table 1 shows the patients’ preoperative characteristics by capsulotomy centration: pupil centration (PC) or first Purkinje reflex centration (FPR). There was no statistically significant difference between the 2 groups preoperatively.