Diurnal variations in tear film break-up time determined in healthy subjects by software-assisted interpretation of tear film video recordings.

BACKGROUND: This study was designed to examine diurnal variations in tear film break-up time (BUT) and maximum blink interval (MBI) and to assess two different ways of calculating these variables on video recordings of the BUT test interpreted with the help of especially designed software. The repeatability of interpreting BUT video recordings was also addressed. METHODS: Twenty-six healthy young adults were enrolled after ruling out dry eye according to a battery of tests (ocular surface disease index, McMonnies questionnaire, Schirmer test, phenol red test and corneal staining). BUT and maximum blink interval were determined on video-recordings of the BUT test conducted over a day in four sessions (9.30 am, 12.30 pm, 3.30 pm and 6.30 pm). In each session, the test was repeated three times to give three videos in which three BUT and MBI values were obtained by a masked observer. BUT and MBI were determined by averaging the three measurements and by averaging only the two closest measurements. Finally, two further experienced observers re-examined the videos to assess the repeatability of the BUT measurements made. RESULTS: No diurnal variation in BUT was observed regardless of whether three or two video measurements were averaged. Significant correlation was detected between BUT and MBI. Inter-observer repeatability was better when BUT times were no longer than 15 seconds. CONCLUSIONS: Tear film BUT was not influenced by the time of day and moderate to strong correlation with MBI was observed in all four sessions. The software-assisted method proved useful and identified the need to clarify the BUT end-point and to limit the test to 15 seconds to improve observer repeatability.

Accuracy of the ICare rebound tonometer in glaucomatous eyes with topical ocular hypotensive medication.

BACKGROUND: The purpose of this study was to assess the accuracy of the ICare tonometer, using the Perkins applanation tonometer (AT) as the reference, in a sample population being treated with travaprost 0.004% for glaucoma. MATERIAL AND METHODS: Twenty-eight consecutive patients with open-angle glaucoma or ocular hypertension who had been receiving travaprost 0.004% to control elevated intraocular pressure (IOP) were included in the study. IOP was measured in the entire sample with ICare and Perkins AT. The difference between the methods was plotted against the mean to compare the tonometers. The hypothesis of zero bias was examined by a paired t-test. The 95% limits of agreement (LoA) were also calculated. RESULTS: As previously found in young healthy subjects, ICare showed a tendency to overestimate Perkins IOP measurements by a mean of 3.57 mmHg. The agreement between the two methods is shown by the 95% LoA which was from -9.37 to +2.23 mmHg: 53% of the IOP differences fell within +/-3 mmHg. CONCLUSIONS: The performance of the ICare tonometer in glaucomatous patients being treated with travaprost 0.004% to lower the IOP appears to be similar to that of young healthy patients. The tendency of ICare to overestimate the IOP readings should be considered when the instrument is used in the follow-up of glaucomatous patients.