Vector analysis of changes in corneal astigmatism following lateral tarsal strip procedure in patients with involutional ectropion or entropion

Purpose: To perform vector analysis of changes in corneal astigmatism and evaluate changes in corneal topographic parameters following the lateral tarsal strip (LTS) procedure in patients with involutional ectropion or entropion. Methods: Nineteen eyes of 15 patients (10 eyes with ectropion and 9 eyes with entropion) were included in this prospective nonrandomized interventional case series. Corneal topographic measurements (Tomey TMS 4a topographer, Tomey Corp, Nagoya, Japan) were performed at the baseline and 3 months after the LTS procedure. Relevant changes in the topographic astigmatism magnitude or axis (defined as a change more than 0.2 D or a shift in the axis greater than 10°, respectively) were analyzed following surgery. Polar astigmatic vector analysis was performed using the Astig PLOT software to calculate surgically induced astigmatism (SIA). Results: There were no significant changes in average keratometry, steep and flat meridian keratometric values, absolute cylinder, surface regularity index and surface asymmetry index after the surgery (All P > 0.05). A relevant change in the magnitude of astigmatism and an axis change greater than 10° occurred in 14 (73.6%) and 10 (52.6%) of the operated eyes, respectively. Polar vector analysis revealed that SIA was 0.47 ± 1.34 D at 91 ± 23°, indicating induction of “with the rule” astigmatism following the surgery. Conclusion: The LTS procedure for the correction of involutional ectropion or entropion could induce relevant changes in corneal astigmatism, sufficient to affect visual function in short term. Longer-term follow-up is required to further characterize the effect of LTS procedure on the corneal topographic features.