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A. Minavi, N. Leach, S. El Hage, W. Miller; Comparison of Central/ Peripheral Corneal Thickness and Central/ Peripheral Epithelial Thickness Measurements Using Three Different Instrumentation . Invest. Ophthalmol. Vis. Sci. 2004;45(13):3797.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose:To compare central and peripheral corneal thickness (CCT, PCT) and central and peripheral epithelial thickness (CET, PET) measurements using an in–vivo confocal microscope, ultrasound pachymeter, and Orbscan topoographer Methods:Confocal microscopy (ConfoScan3), Orbscan topography and ultrasonic pachymetry (Sonogage Corneo–Gage Plus 2) were used to obtain baseline CCT, PCT, CET and PET on 7 healthy subjects (28 + 4 years; 6 females, 1 male); one eye was randomly chosen for statistical analysis. Informed consent was obtained from all subjects prior to enrollment. Measurements were taken in the following order; Orbscan, Sonogage, and ConfoScan3. All measurements were taken in primary gaze except peripheral measurements with the ConfoScan3, which were taken inferiorly with the subject in superior gaze (28 º above primary gaze). Results:Mean CCT of 563µm (95% confidence interval (CI) 528–611µm) and 505µm (CI 471–579µm); using Orbscan and ConfoScan3 respectively showed no statistical difference. Using the Sonogage, mean CCT of 545µm (CI 503–588µm) was statistically different from Orbscan (p=0.007) and ConfoScan3 (p=0.049). Mean PCT measurements using Orbscan 645µm (CI 590–701µm), ConfoScan3 620µm (CI 570–669 µm), and Sonogage 636µm (CI 581–691µm) showed no statistical difference. Orbscan mean CCT and PCT measurements were only slightly greater when compared to the Sonogage and ConfoScan3. There was no statistical difference between the ConfoScan3 and Sonogage in CET (p=0.677) and PET (p=0.318), however there was greater variability in ConfoScan3 measurements; CET: mean 48.6µm, 46.6µm, CI 35.1–62.2µm, 45.7–47.7µm and PET: mean 54.1µm, 48.0µm, CI 40.0–68.2µm, 46.9–49.1µm, ConfoScan3 and Sonogage respectively. Conclusions:Variations in mean CCT, PCT, PCT and PET measurements can be attributed to differences in methodologies between the instruments tested. Advantages and disadvantages of each instrument, including operator expertise, should be taken into consideration while measuring ocular parameters. Although all measurements, except CCT with the Sonogage, did not vary significantly amongst the 3 clinical instruments, one should be cautious to compare values obtained by different instruments particularly in refractive surgery and clinical research studies where outcomes can be significantly affected.
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