Purpose:
To compare the central corneal thickness measurements using ultrasonic pachymetry and the orbscanII® in normal Egyptian subjects.

Subjects and Methods:
60 eyes of 30 normal subjects visiting the ophthalmology out patient clinic at Benha Faculty Of Medicine were enrolled in this study. All were informed about the study and its aim and those willing to share were enrolled. Every subject was examined by two examiners .The first examiner performed pachmetry using the obrscan II in the first room and kept the results away from the second examiner. The patient was then transferred to another room where he was examined by the second examiner who performed ultrasonic pachymetery using the Tomey ultrasonic pachymeter. At the end of the study both data collected by both examiners was collected and statistically analyzed using the student t test .

Results:
The mean difference in central corneal thickness in normal individuals when measured by both methods was 1.22µm + 3.6 (SD) with P value of more than 0.05 (statistically insignificant) when the orbscan II was used utilizing the default linear correction factor LCF. But when the orbscan II was used without the default LCF, the mean difference in central corneal thickness was 42.0µm + 28.8 (SD) which was statistically significant (P < 0.0001).

Conclusion:
The measurements of central corneal thickness using both the orbscan II and the ultrasonic pachymeter are more or less similar in normal subjects when using the default built in LCF in contrast to the preliminary reports that were released when comparing ultrasonic pachymetry to pachmetry using the orbscan I which did not utilize a linear correction factor in its software.