Temperature Rise of Human Eyes Due to Declines in Visual Accommodation during Display Operations with TFT-LCDs

Abstract

Issues arose from fatigue of human eyes will be developed to visual strain of ciliary muscles surrounding human eyeballs, which might decline visual accommodation by a factor of 10-15 %, since the visual strain will elevate the temperature of eyelids, during the contiguous display operations for a plurality of hours. In the Muraoka's method showing electronic Landolt rings of different sizes appearing on a display frame in an ascending sequence of order in sizes, each Landolt ring will be impulsively demonstrated for a span of 100 milliseconds in sequence on a computer display. It is thus known to effectively be utilized to check if visual accommodation of human eyes declines due to fatigue caused by TFT-LCDs with elapsing of time during display operations. Declines in visual accommodation of this mode were defined as the distinction ratios for TFT-LCDs in terms of both backlights of white LED matrices and two-row cold cathode fluorescent lamps (two-row CCFLs), respectively. The display operations contiguously carried out for a span of 0 to 120 minutes showed excellent performance in distinction ratios for both display types, and however the former was found to be superior to the latter, due to minor differences in distinction ratios with elapsing of time. Search for the cause of these minor differences were satisfactorily done by introducing a new measurement method for the temperature changes around the subjects' eyelids during the contiguous display operations, using a two-dimensional far-infrared thermometer camera. We newly found that declines in visual accommodation would be caused by the fatigue of ciliary muscles surrounding crystalline lenses of human eyes, because this kind of fatigue was found to be detectable by using this two-dimensional far-infrared thermometer camera. We newly succeeded in sensing, with an excellent sensitivity at approximately 10 micrometers, a temperature rise of up to as low as 0.9-1.2 degrees Celsius on the subjects' eyelids found during display operations of this mode. Our measurement was aimed at to sense temperature rises of human eyelids in place of those of ciliary muscles, and in addition partly including those of ciliary muscles due to favourable properties of far-infrared rays.