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

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... ticipants 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. Article Citation: Ahmad MI, Qureshi MA, Ahmad MS, Aldebasi YH. Comparison of central corneal thickness measurements by pentacam and ultrasound pachymetry, in myopic and keratoconus eyes. Professional Med J 2018; 25(2):252-260.