Repeatability and agreement of central corneal thickness measurements with a new handheld non-contact pachymeter

Abstract

AbstractPurposeTo compare the repeatability of central corneal thickness (CCT) measurements taken with a new hand-held pachymeter (Occuity PM1 Pachymeter) and to assess its agreement with ultrasound biometry and two commercially available optical biometers in participants with normal eyes.MethodsThree consecutive CCT measurements of the right eye of 105 participants with normal corneas were acquired by the PM1 pachymeter, Lenstar LS900 and Oculus Pentacam HR in a random order. This was followed by three measurements with a hand-held ultrasound pachymeter (UP) (Pachmate-2). Repeatability and the repeatability limit were calculated with each device and Bland-Altman limits of agreement (LoA) were determined for the PM1 pachymeter compared to the other devices.ResultsThe mean CCT (±SD) was 551.04±33.43 μm, 558.62±31.46 μm, 549.41±31.00 μm, 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 μm and 26.89 μm).ConclusionsThe 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.Key pointsMeasurement of central corneal thickness (CCT) is an important clinical measurement in the diagnosis and management of glaucoma and certain corneal dystrophies, it also provides useful information prior to refractive surgeryThe Occuity PM1 pachymeter is a new hand-held non-contact perimeter that uses confocal technology to measure CCT. The device showed excellent precision for CCT measurements across a range of corneal thicknesses in normal eyesThe PM1 pachymeter provides a safe and easy to use alternative to ultrasound pachymetry that could facilitate an increased uptake of pachymetry in routine optometric practice