CENTRAL CORNEAL THICKNESS

COMPARISON OF CENTRAL CORNEAL THICKNESS MEASUREMENTS BY PENTACAM AND ULTRASOUND PACHYMETRY, IN MYOPIC AND KERATOCONUS EYES.

Abstract

Objectives: To compare central corneal thickness in myopic and keratoconus
eyes by ultrasound pachymetry and pentacam HR. Study Design: Cross sectional study.
Setting: Qassim University, Optometry Clinics, Kingdom of Saudi Arabia. Period: October
2016 to April 2017. Methodology: One hundred myopic and keratoconus participants. Central
Corneal Thickness (CCT) were measured with two techniques by ultrasonic pachymetry and
pentacam HR in two groups. Group one consisted of 80 myopic participants and group two of 20
Keratoconuspatients.Pentacamreadings were recorded first. CCT were compared and analyzed
statistically using unpaired t-test and histogram. Results: One hundred participants (100) were
included in which 80 participants were myopic and 20 with keratoconus. Both eyes (200) of all
the participants were examined. Age of the myopics ranged from 18-30 years (Mean=23.03).
The mean value with ultrasound pachymetery was 555μm (SD±32.021) and with pentacam
566μm (SD±37.367). We observed a tendency of overestimation of CCT measurements with
pentacam. Statistically a significant difference of reading between two devices (P<0.001) was
found. In keratoconus participants, the mean age was 23.7 years (21- 26). The mean CCT taken
with Pentacam HR and US Pachymetry was 476μm (SD± 16.980) and 465μm (SD± 35.868)
respectively. The t-test showed no statistical difference between thepentacam HR and
ultrasound pachymetry (p>0.214). Conclusion: Measurements of central corneal thickness
done with Ultrasound Pachymeter and Pentacam HR are closely related to each other and
are interchangeable when used in normal refractive error cases. While in Keratonus patients
ultrasound pachymetry is preferred because of its reliability.