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.