Central corneal thickness: z-ring corneal confocal microscopy versus ultrasound pachymetry.
OBJECTIVE
To compare the repeatability and validity of corneal pachymetry by a corneal confocal microscope with a z-axis adapter (Confoscan 4.0 with z-ring adapter: z-CS4) versus ultrasound (US) pachymetry in the measurement of central corneal thickness (CCT).


METHODS
CCT in 44 eyes of 44 subjects was determined with z-CS4. Z-CS4 exams were used to estimate the repeatability of thickness measurement by z-ring adapter for this confocal microscope. Intraclass Correlation Coefficient (ICC) between two different z-CS4 users was also determined. CCT in the same 44 eyes was determined with US pachymetry and measurements were compared with z-CS4 CCT.


RESULTS
Z-CS4 CCT showed high intrainstrument reproducibility (ICC = 0.989; 95%CI 0.982-0.993; P < 0.0001). Mean difference among three CCT consecutive measures, in the same eye, was 0.8 +/- 11.1 microm. High correlation was found between two users (ICC = 0.896; 95%IC 0.830-0.937; P < 0.0001). Z-CS4 CCT showed high correlation with US pachymetry (ICC = 0.921; 95%CI 0.851-0.958; P < 0.0001). Mean corneal thickness determined was statistically different with the two methods (US: 512.6 +/- 65.8 microm; z-CS4: 487.8 +/- 60.1 microm; P < 0.0001).


CONCLUSIONS
Z-CS4 seems an accurate, noninvasive and reproducible technique for CCT evaluation and confirms that central cornea is thinner when measured with confocal microscopy compared to ultrasounds.
Brugin
Erica
E
Department of Ophthalmology, University of Padova, Padova, Italy.
Ghirlando
Alessandra
A
Gambato
Catia
C
Midena
Edoardo
E
D000328:Adult; D000886:Anthropometry; D003315:Cornea / Q000033:anatomy & histology* / Q000000981:diagnostic imaging*; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008297:Male; D033401:Microscopy, Acoustic; D018613:Microscopy, Confocal; D008875:Middle Aged; D015203:Reproducibility of Results