Comparison between Ultrasonic Pachymetry and Scheimpflug Based Pentacam for Assessment of Central Corneal Thickness in Myopic Persons of Indian Sikh Origin

Aims: To compare the central corneal thickness (CCT) measurements between Ultrasound Pachymetry and by the Scheimpflug based Pentacam in myopic persons of Indian Sikh origin.

Methodology: In a prospective study, 100 eyes of 50 myopic persons of Indian Sikh origin (aged 16 to 45 years) were subjected to CCT measurement with two methods Ultrasonic Pachymetry and Pentacam HR. Pentacam HR readings were recorded first. CCT readings obtained by both the methods were compared and analysed statistically using unpaired t-test.

Results: Mean Pachymetry reading with Ultrasound Pachymeter was 557.9 (SD 9.727) micrometers and with Pentacam was 562.34 (SD 9.91) micrometers. The correlation coefficient (r) between measurements using both instruments was 0.974. There was a tendency of overestimation of CCT measurements with Pentacam with a statistically significant difference between both methods (P<0.001). However, the amount of overestimation seems to be of little clinical importance (4.44 μm). The mean difference was was -4.44 micrometers (95% LOA -0.108 to -8.77 micrometers).

Conclusion:

1. CCT measurements obtained with either the non contact Pentacam HR or contact Ultrasonic Pachymeter are close to each other with tendency of obtaining slightly higher readings with Pentacam HR.

2. Pentacam was more convenient to the patient with excellent agreement to the readings by Ultrasonic Pachymeter which is considered the gold standard method of CCT measurement.