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Repeatability of intraoperative central corneal and residual stromal thickness measurement using a handheld
Dan Z Reinstein1, Timothy J Archer, Marine Gobbe
1London Vision Clinic, Department of Ophthalmology, St. Thomas' Hospital, Kings College, London, United Kingdom. dzr@londonvisionclinic.com
Purpose:
To determine and compare the repeatability of intraoperative central corneal thickness (CCT) and residual stromal bed thickness measurements using a handheld ultrasound (US) pachymeter.
Setting:
London Vision Clinic, London, United Kingdom.
Design:
Comparative evaluation of a diagnostic test or technology.
Methods:
This study comprised eyes that had laser in situ keratomileusis retreatment by flap lift in which handheld US pachymetry (Corneo-Gage Plus 50 MHz) had been performed intraoperatively. In each case, 5 consecutive measurements were obtained centrally immediately before and after the flap was lifted. The within-eye repeatability was calculated as the standard deviation of the 5 repeated measurements for the CCT measurements and the central residual stromal thickness (RST) measurements.
Results:
The study evaluated 134 eyes (79 patients). The mean CCT was 467 μm ± 40 (SD) (range 393 to 577 μm). The repeatability of CCT measurements was 6.83 μm, the coefficient of repeatability was 13.40 μm, and the coefficient of variation (CoV) was 1.46%. The mean central RST was 335 ± 46 μm (range 259 to 465 μm). The repeatability of central RST measurements was 4.91 μm, the coefficient of repeatability was 9.62 μm, and the CoV was 1.46%.
Conclusion:
The repeatability of intraoperative handheld US pachymetry was similar between measurements of CCT and measurements of central RST; the CoV was 1.46% in both cases.
