Torsional phacoemulsification: A pilot study to revise the "harm scale" evaluating the endothelial damage and the visual acuity after cataract surgery

Abstract

Purpose: To study the effect of torsional phacoemulsification energy on corneal endothelium evaluating the relationship between changes of endothelial cells and postoperative visual acuity.

Methods: This prospective clinical observational cohort study included 50 patients with cataract who underwent torsional phacoemulsification. Sequential quantitative and qualitative morphometric endothelial cell analyses of the cornea were performed four weeks preoperatively and six weeks postoperatively using noncontact specular microscopy.

Results: This work confirmed the strong relationship, described by a linear model (one-way ANOVA, R2 = 77.9%, P < 0.0001), between the percentage of endothelial cell loss (ECL%) and the 5-score harm scale. According to the Tukey post-hoc pairwise comparison test, distinct values of ECL% are grouped in 3 subsets. The value of ECL = 10% has been identified as cut-off to discriminate patients with excellent postoperative best-corrected visual acuity (BCVA > 85 letters) from those with just a good/satisfied visual outcome (BCVA ≤ 85 letters). Within the 5-score harm scale, there was a significant correlation among phaco energy intraoperatively delivered and the average endothelial cell loss.

Conclusions: This study confirms the validity of the 5-score harm scale first proposed by Sorrentino and colleagues in 2016. This time, the method categorizes cataracts taking into account nucleus hardness and phaco cumulative dissipated energy. Predicting the harm on corneal endothelium, we can discriminate patients with excellent BCVA and with just good/satisfied BCVA. With torsional phacoemulsification with respect to longitudinal, the percentage of patients who can reach excellent BCVA is remarkably increased.

Fig 1. Dotplot of distribution of endothelial cell loss percent depending on the 5-score harm scale.

There are 3 patients in level 1 (blu circle dots), 13 in 2 (red square dots), 10 in 3 (green rhombus dots), 7 in 4 (purple triangle dots), and 17 in 5 (grey right arrow dots). ECL = endothelial cell loss.

Fig 2. Interval plots of endothelial cell loss resulting from one-way ANOVA test for increasing score values.

Tukey post-hoc test groups score 1–2 into subset I, score 3–4 into subset II and score 5 into subset III. The cut-off ECL = 10% splits into low scores (subset I, 28% of patients) and high scores (subsets II and III). ECL = endothelial cell loss.

Fig 3. Scatterplot of distribution of percentage of endothelial cell loss depending on the total phaco cumulative dissipated energy, according to the 5-score harm scale.

The non-linear curve well describes the rising trend of endothelial cell loss for increasing cumulative dissipated energy till a fixed level where a maximum ECL% is achieved. Dots (score 1–4) are all grouped along the first linear growth. Only dots of score 5 are uniformly distributed around the final asymptote. CDE#2 = total phaco cumulative dissipated energy; ECL = endothelial cell loss.

Fig 4

Frequency distribution of postoperative best-corrected visual acuity in group A (ECL < 10%) and B (ECL ≥ 10%) at 6-week follow-up. Line at 85 letters discriminates an excellent visual outcome (group A) from a good/satisfying visual function (group B). BCVA = best-corrected visual acuity; ECL = endothelial cell loss.