Repeatability of intra-ocular pressure and central corneal thickness measurements provided by a non-contact method of tonometry and pachymetry.
BACKGROUND
To examine the repeatability of intra-ocular pressure (IOP) and central corneal thickness (CCT) measurements provided by the Tono-Pachymeter NT530P (Nidek, Japan), and to assess agreement of the device with Goldmann applanation tonometry (GAT) and ultrasound pachymetry (UP).


METHODS
Sixty-two normal eyes of 62 subjects were included in the study. Three sessions of measurements, each consisting of three sets of measurements, were completed with each device. Repeatability was determined with the coefficient of variation (CoV) and the coefficient of repeatability (CoR) values. Agreement between devices was examined by Bland-Altman analysis and intraclass correlation coefficient (ICC) analyses.


RESULTS
The CoV and CoR for IOP values were 18.4% and 5.5 mmHg with the NT530P and 16.6% and 4.3 mmHg with the GAT respectively. On average, NT530P overestimated the IOP compared with GAT by 1.3 mmHg. The 95% limits of agreement between the methods ranged from -5.9 to +3.3 mmHg, and the ICC for average IOP measures between devices was 0.64 (P < 0.001). The CoV and CoR for CCT measurements were 5.5% and 59.8 μm with the NT530P and 5.5% and 60.5 μm with UP. NT530P CCT readings were on average 13 μm thinner than those obtained with UP. The 95% limits of agreement (LoA) ranged from -7.4 to +33.1 μm, and the ICC for average CCT measures between devices was 0.93 (P < 0.001).


CONCLUSIONS
The NT530P demonstrated high IOP and CCT measurement repeatability in the normal population studied. The device tended to slightly overestimate IOP compared to GAT. CCT values provided by NT530P were interchangeable with those of UP.
Schiano Lomoriello
Domenico
D
IRCCS Fondazione G.B. Bietti, Rome, Italy.
Lombardo
Marco
M
Tranchina
Laura
L
Oddone
Francesco
F
Serrao
Sebastiano
S
Ducoli
Pietro
P
D000328:Adult; D000886:Anthropometry; D003315:Cornea / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D007429:Intraocular Pressure / Q000502:physiology*; D008297:Male; D015203:Reproducibility of Results; D014065:Tonometry, Ocular / Q000295:instrumentation*; D014463:Ultrasonography