Agreement of noninvasive tear break-up time measurement between Tomey RT-7000 Auto Refractor-Keratometer and Oculus Keratograph 5M.
BACKGROUND
It is difficult to standardize assessment of dry eye in different clinical settings. Increasingly, tear stability is recognized to be important for the definition and assessment of patients with dry eye. Recently, two commercially available instruments have been made available for objectively measuring noninvasive tear break-up time (NIBUT), as an indicator of tear stability: the Tomey RT-7000 Auto Refractor-Keratometer and Oculus Keratograph (K)5M. We aim to assess the agreement of NIBUT measurements using these modalities.


METHODS
This prospective cross-sectional study was carried out in a tertiary referral eye center and involved 126 consecutive dry eye patients. NIBUT assessment was performed on the right eyes of participants with both the RT-7000 and the K5M techniques, with the order of assessment randomized. The Standardized Patient Evaluation of Eye Dryness (SPEED) questionnaires were administered to assess dry eye symptoms in the 2 weeks before assessment.


RESULTS
The age of the participants was 56.0±14.3 years (69.84% females). Measurements for both modalities were non-normally distributed (right-skewed). The median RT-7000 and K5M readings were 4.2 (range 0.1-10.0) and 6.4 (0.1-24.9) seconds, respectively. RT-7000 and K5M readings were poorly correlated (ρ=0.061,P=0.495). Intraclass correlation coefficient between the modalities was 0.187 (95% confidence interval -0.097 to 0.406). The Bland-Altman plot showed no systematic differences between the readings with these machines. The agreement between machines was not different in different SPEED categories.


CONCLUSIONS
While there are theoretical and practical benefits of NIBUT for assessment of tear stability over dye-based methods, the agreement between the two modalities was poor. Hence, studies and trials assessing NIBUT should avoid using these modalities interchangeably for NIBUT assessment. More research is needed to improve consensus on how to determine NIBUT.
Ocular Surface Research Group, Singapore Eye Research Institute; Yong Loo Lin School of Medicine, National University of Singapore.
Ryan
R
Lee
Ocular Surface Research Group, Singapore Eye Research Institute.
Sharon
S
Yeo
School of Health Sciences, Ngee Ann Polytechnic.
Han Tun
HT
Aung
Ocular Surface Research Group, Singapore Eye Research Institute; Yong Loo Lin School of Medicine, National University of Singapore; Duke-NUS Medical School, Singapore; Cornea and External Eye Disease Service, Singapore National Eye Centre, Singapore.
Louis
L
Tong
Oculus Keratograph; Tomey RT-7000; dry eye; tear break-up time; tear film
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