Reliability of a New Noninvasive Tear Film Break-up Time Measurement Using a Keratograph

Seongyong Jeong; Sang Bumm Lee

doi:10.3341/jkos.2016.57.9.1354

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Jeong and Lee: Reliability of a New Noninvasive Tear Film Break-up Time Measurement Using a Keratograph

Original Article

J Korean Ophthalmol Soc 2016;57(9):1354-1360.

Published online: 25 September 2016

DOI: https://doi.org/10.3341/jkos.2016.57.9.1354

Reliability of a New Noninvasive Tear Film Break-up Time Measurement Using a Keratograph

Seongyong Jeong, MD, Sang Bumm Lee, MD, PhD

Department of Ophthalmology, Yeungnam University College of Medicine, Daegu, Korea

Address reprint requests to Sang Bumm Lee, MD, PhD Department of Ophthalmology, Yeungnam University Hospital, #170 Hyeonchung-ro, Nam-gu, Daegu 42415, Korea Tel: 82-53-620-3445, Fax: 82-53-626-5936 E-mail: sbummlee@ynu.ac.kr

Received 21 April 2016 Revised 25 May 2016 Accepted 27 June 2016

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Purpose

To evaluate the repeatability of non-invasive tear film break-up time and identify its relationships with dry eye parameters.

Methods

A total of 100 participants (50 with dry eye, and 50 in the control group) were enrolled prospectively. Noninvasive keratograph first (NIKf-BUT) and average (NIKav-BUT) break-up times were evaluated 2 times using Keratograph 4 (Oculus, Wetzler, Germany), and then tear film break-up time with fluorescein (FBUT) was measured. The correlation analyses were performed between non-invasive parameters (NIKf-BUT and NIKav-BUT) and FBUT. Intraobserver agreements of NIKf-BUT and NIKav-BUT were assessed using intraclass correlation coefficients (ICC). The receiver operating characteristic (ROC) curve technique was used to evaluate the non-invasive method in the diagnosis of dry eye.

Results

The correlation analyses revealed positive correlation between NIKav-BUT and FBUT in both groups (dry eye; r = 0.66, p < 0.001 and control group; r = 0.77, p < 0.001). The ICCs of NIKf-BUT and NIKav-BUT were 0.72 and 0.94 in the dry eye, respectively, and 0.70 and 0.91 in the control group. NIKav-BUT was not different from FBUT in either group. The areas under the ROC curves of NIKf-BUT and NIKav-BUT were 0.917 and 0.980, respectively.

Conclusions

The high ICCs verified the repeatability of NIKf-BUT and NIKav-BUT. NIKav-BUT showed no difference from FBUT and positive correlation with FBUT. NIK-BUT showed high diagnostic power and can be considered a new parameter to evaluate dry eye syndrome.

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Keywords: Correlation, Dry eye, Keratograph 4, Noninvasive tear film break-up time, Repeatability

References

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Figure 1.

Representative image of non-invasive keratograph tear film break-up time (NIK-BUT) using Oculus Keratograph 4 (Oculus, Wetzler, Germany). (A) A real time image recorded the entire course of break up process. Placido rings were reflected from surface of cornea and their distortions were recorded as the red-framed rectangular break-up units. (B) The final report was summarized as tear film break-up colour-code map. (C) Noninvasive keratograph first break-up time (NIKf-BUT), non-invasive keratograph average break-up time (NIKav-BUT) and break-up progress of break-up units were provided.

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Figure 2.

Distribution of non-invasive keratograph tear film break-up time (NIK-BUT) and tear film break-up time with fluorecein (FBUT) using box and whisker plot in the dry eye and control groups. The boxes include 50% of the measured values between 1st and 3rd quartiles and the median (horizontal line). The upper and lower fences indicate 1.5 times the interquartile range (IQR) from 3rd and 1st quartiles. The outliers which are more than 1.5 IQR from the box are shown as circles. The mean of each parameter are shown as diamond. Comparison between FBUT and NIK-BUTs was performed by paired sample t-test. NIKf-BUT = non-invasive keratograph first break-up time; NIKav-BUT = non-invasive keratograph average break-up time.^* p-value < 0.05 by paired sample t-test.

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Figure 3.

Receiver operating characteristic curve (ROC) of non-invasive keratograph tear film break-up time (NIK-BUT). The area under the curve (AUC) is 0.917 in 1st non-invasive keratograph first break-up time (NIKf-BUT) and 0.980 in 1st non-invasive keratograph average break-up time (NIKav-BUT). The cutoff value derived from ROC curve was provided. The difference of AUC between NIKf-BUT and NIKav-BUT was 0.063 and was significant (p = 0.032).

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Table 1.

Demographics and ocular parameters of the study subjects

	Dry eye group	Control group	p-value
Eyes (n)	50	50
Age (years)	54.6 ± 10.9	52.8 ± 11.8	0.347^*
Gender (male:female)	18:32	23:27	0.309^†
FBUT (seconds)	5.7 ± 1.7	13.1 ± 2.9	<0.001^*
1st NIKf-BUT (sec)	4.1 ± 1.3	10.8 ± 4.9	<0.001^*
1st NIKav-BUT (sec)	5.8 ± 2.0	13.5 ± 3.7	<0.001^*
2nd NIKf-BUT (sec)	4.3 ± 1.5	10.8 ± 4.2	<0.001^*
2nd NIKav-BUT (sec)	5.8 ± 2.1	13.6 ± 2.9	<0.001^*
Schirmer test (mm/5 min)	7.0 ± 3.6	13.2 ± 5.6	<0.001^*
OSDI score	40.1 ± 14.2	25.1 ± 13.3	<0.001^*

Values are presented as mean ± SD unless otherwise indicated. For the NIKf-BUT, the intraclass correlation coefficient between first and second examination was 0.717 in the dry eye and 0.700 in the control group. For the NIKav-BUT, the intraclass correlation coefficient between first and second examination was 0.943 in the dry eye and 0.912 in the control group.

FBUT = fluorescein tear film break-up time; NIKf-BUT = non-invasive keratograph first break-up time; NIKav-BUT = non-invasive keratograph average break-up time; OSDI = ocular surface disease index.

^* p-value based on independent sample t-test

^† p-value based on chi-square test.

Table 2.

Pearson's correlation coefficients for all reference methods

	FBUT	1st NIKf	1st NIKav	2nd NIKf	2nd NIKav	Schirmer	OSDI
FBUT	1	0.440^†	0.660^†	0.592^†	0.689^†	0.289^*	−0.046
1st NIKf	0.612^†	1	0.687^†	0.567^†	0.601^†	0.111	−0.118
1st NIKav	0.768^†	0.832^†	1	0.638^†	0.893^†	0.228	0.003
2nd NIKf	0.503^†	0.545^†	0.558^†	1	0.685^†	0.374^†	−0.052
2nd NIKav	0.724^†	0.654^†	0.860^†	0.730^†	1	0.206	0.063
Schirmer	0.377^†	0.230	0.311^*	0.247	0.337^*	1	−0.112
OSDI	−0.162	−0.309^*	−0.265	−0.270	−0.233	−0.045	1

Values in light gray background area represent correlation in the normal control group, and the other values represent correlation in the dry eye group.

FBUT = fluorescein tear film break-up time; NIKf = non-invasive keratograph first break-up time; NIKav = non-invasive keratograph average break-up time; OSDI = ocular surface disease index.

^* p-value < 0.05

^† p-value < 0.01.

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