Central corneal thickness measurements using Orbscan II scanning slit topography, noncontact specular microscopy, and ultrasonic pachymetry in eyes with keratoconus.
OBJECTIVE
To compare corneal thickness measurements using Orbscan II scanning slit topography, Topcon SP-2000P noncontact specular microscopy, and ultrasonic pachymetry in eyes with keratoconus.


METHODS
Central corneal thickness was measured in 22 eyes with keratoconus. Eyes with apparent corneal opacity were excluded. Scanning slit topography, noncontact specular microscopy, and ultrasonic pachymetry were used in this sequence. The acoustic equivalent correlation factor (0.92) was used for Orbscan readings.


RESULTS
Three devices gave significantly different corneal thickness readings (P < 0.001, repeated-measure analysis of variance). Measurements with Orbscan scanning slit topography (449.5 +/- 43.2 [SD] mum) were significantly smaller than those of ultrasonic pachymetry (485.0 +/- 29.3 microm; P < 0.001, Tukey multiple comparison) and SP-2000P noncontact specular microscopy (476.7 +/- 28.3 microm; P = 0.002). There were significant linear correlations between ultrasonic pachymetry and scanning slit topography (Pearson correlation coefficient r = 0.741, P < 0.001), between scanning slit topography and noncontact specular microscopy (r = 0.880, P < 0.001), and between noncontact specular microscopy and ultrasonic pachymetry (r = 0.811, P < 0.001).


CONCLUSIONS
In eyes with keratoconus, Orbscan II scanning slit topography system gave significantly smaller corneal thickness readings than the other 2 devices. Measurements taken by noncontact specular microscopy and ultrasonic pachymetry were comparable. Three devices showed significant linear correlations with one another.
Kawana
Keisuke
K
Department of Ophthalmology, Institute of Clinical Medicine, University of Tsukuba, Ibaraki, Japan.
Miyata
Kazunori
K
Tokunaga
Tadatoshi
T
Kiuchi
Takahiro
T
Hiraoka
Takahiro
T
Oshika
Tetsuro
T
D000328:Adult; D003315:Cornea / Q000000981:diagnostic imaging / Q000473:pathology; D019781:Corneal Topography / Q000379:methods*; D005500:Follow-Up Studies; D006801:Humans; D007640:Keratoconus / Q000000981:diagnostic imaging / Q000473:pathology*; D008853:Microscopy / Q000379:methods*; D015203:Reproducibility of Results; D012720:Severity of Illness Index; D014463:Ultrasonography