EXTERNAL OCULAR HYPEREMIA - A QUANTIFIABLE INDICATOR OF SPACECRAFT AIR-QUALITY

Background: Eye irritation consistently ranks as a top astronaut compl aint but is difficult to measure. Exposure to internal air pollution h ypothetically disrupts the eye's tear film, thereby exposing the crewm embers' conjunctivae to the irritating effects of the recirculated, co ntaminant-laden atmosphere of the space vehicle. Causes elude engineer s and toxicologists, who report that measured irritants remain below e stablished Spacecraft Maximum Allowable Concentrations. Lack of object ive ocular endpoints stymies efforts to identify etiologies. Hypothesi s: Computers offer a practical means of analyzing ocular hyperemia in space. Methods: We use computer analysis to quantify redness and blood vessels of digitized images of bulbar conjunctivae in near real time. Custom software masks artifacts, lids and lashes for each photographi c or telemedicine ocular image. Algorithms then generate semi-independ ent measurements of hyperemia. Computed difference scores between 34 p airs of images were compared with subjective difference scores as vote d on by a panel of ophthalmology residents. Results:Objective data wer e reliably extracted from ocular images and significantly correlated ( r = 0.583, P < 0.05) with subjective scores. Conclusions: This ground- based methodology generates accurate and reliable ocular endpoint data without mass, volume, or power penalty. To assist in identifying and eliminating onboard ocular irritants, these objective data can be regr essed against independent variables such as mission elapsed time, subj ective astronaut complaints, levels of chemical and electromagnetic co ntaminants, nephthelometric and barothermal data. As missions lengthen , sensitive tools such as hyperemia quantification will become increas ingly important for assessing and optimizing spacecraft environments.