Devices and variables Clause Samples

Devices and variables. The VK used in this study was the Keratograph 5M system (Oculus, Optikgerate, Germany), which provides a measure of the non-invasive break-up time (NIBUT) by means of detecting perturbations of the ▇▇▇▇▇▇▇ rings projected on the tear film. Each subject was asked to maintain the eyes opened after blinking two times in a low-light room (1 lux) during the measure with infrared light. For some subjects, the blink can terminate the measurement before a potential break-up of the tear film. In cases like these, the trial was repeated if the system provided the message “too short time” or was accepted, classifying the tear film as stable and recording the blinking time (BT). In the remaining cases, the system provided two variables, the first (NIBUT) and the mean (MNIBUT) non-invasive break-up times. The MNIBUT was calculated considering all broken segments and the stability was classified in a grade scale as stable (level 0: break-up average ≥14s), critical (level 1: break-up average ≥7 bis <14s) or unstable (level 2: break-up average <7s). For uniform classification of ordinal variables with the OQAS, level 0 was considered as grade 1 in this study, and consequently grades with this device were the level offered by the manufacturer plus one (grade = level + 1). The double pass system used was the OQAS HD Analyzer (Visiometrics SL, Terrassa, Spain) which provides a measurement of the optical effect of tear film instability using the double-pass retinal images of a point source and calculating the Ocular Scattering Index (OSI).[12] During the measurement, the subject's refractive error was corrected internally by an optometer (ranging from −8.00 to +5.00 diopters [D] in the instrument) prior to the OSI tear film measurement. Besides that, astigmatism above 0.50 D was corrected using trial lenses. Measurements were taken in a low light room (5 lux) different from the VK. The system allowed the clinician to obtain three types of measures: (1) without blinking (2) after blinking each 3 seconds, “baseline mode” and (3) after blinking each 9 seconds, “stress mode”. With these three measurement modes, the system recorded double-pass images every 0.5 seconds during a 20-second period. Thus, the system recorded 40 images showing the evolution of the eye optical quality during the 20 seconds of measurement. The procedure used in the current study was the “baseline mode”, with the patient blinking each 3 seconds after a beep emitted by the device. The variables provided by ...