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Comparison of central corneal thickness measured by four different pachymeters
Elliott H Myrowitz1, Shiquan Ren, Roy S Chuck
1Wilmer Eye Institute, The John Hopkins School of Medicine, Lutherville, MD, USA. emyrowitz@jhmi.edu
Purpose:
To compare three different ultrasound pachymeters and an optical scanning device for measuring central corneal thickness (CCT).
Methods:
This was a prospective study of 45 consecutive patients (90 eyes), who were seen in consultation for corneal refractive surgery and were tested by the same clinician on one visit. Thirty-five patients with no previous corneal eye surgery (group 1) and 10 who had undergone LASIK (group 2) were analyzed separately. Pachymetry was measured with the Pach V, PachPen, PachMate, and Orbscan II instruments.
Results:
Generalized Estimation Equations showed significant differences between the Orbscan II and the ultrasound instruments (5.2-22.8 microm) in group 1 and 2, and between the Pach V and the PachPen or PachMate (2.3-3.8 microm) in group 1. In group 2, 10 of 20 eyes had a range of measurements over 20 microns.
Conclusions:
In 45 consecutive patients tested on one visit by the same clinician, CCT measured with three ultrasonic pachymeters, including two hand-held units, was clinically comparable in group 2. CCT measured with two ultrasonic pachymeters (i.e., PachMate and PachPen) was clinically comparable in group 1. The Orbscan II data differ from the other three instruments in both groups but more in the patients who had undergone LASIK (group 2).
