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Repeatability and agreement of central corneal thickness measurements with a new handheld non-contact pachymeter
John G Lawrenson1, Simranjit Gill2, Isra Masuid2,3
1Centre for Applied Vision Research, School of Health and Psychological Sciences, City, University of London, London, UK.
Purpose:
To compare the repeatability of central corneal thickness (CCT) measurements taken with a new handheld pachymeter (Occuity PM1 pachymeter) and to assess its agreement with ultrasound biometry and two commercially available optical biometers in participants with normal eyes.
Methods:
Three consecutive CCT measurements of the right eye of 105 participants with normal corneas were acquired by the PM1 pachymeter, Lenstar LS 900 and Oculus Pentacam HR in a random order. This was followed by three measurements with a handheld ultrasound pachymeter (UP) (Pachmate 2). Repeatability and the repeatability limit were calculated for each device and Bland-Altman limits of agreement (LoA) were determined for the PM1 pachymeter compared to the other devices.
Results:
The mean CCT (±SD) was 551.04 ± 33.43, 558.62 ± 31.46, 549.41 ± 31.00 and 539.73 ± 29.50 μm for the PM1 pachymeter, UP, Lenstar and Pentacam, respectively. The repeatability limits (expressed as the within subject SD for repeat measurements) were 14.02, 13.68, 4.99 and 9.90 μm, respectively. The closest agreement was between the PM1 and Lenstar (mean difference = -1.63 μm with LoA 10.72 μm below and 13.97 μm above the readings obtained with the Lenstar). The PM1 underestimated CCT compared to UP (mean difference = 7.58 μm, LoA 24.63 μm below and 9.47 μm above UP). The agreement was lowest between the PM1 and Pentacam (mean difference = -11.30 μm, LoA between 4.29 and 26.89 μm).
Conclusions:
The PM1 pachymeter shows excellent precision for CCT measurements across a range of corneal thicknesses in normal eyes and provides a safe and easy-to-use alternative to ultrasound pachymetry.
