Gas stress test for assessment of corneal endothelial function

Purpose: This study was undertaken to evaluate the endothelial pump functio n by monitoring both corneal swelling response under hypoxia and dehydratio n response following hypoxia in vivo. Methods: Humidified nitrogen gas was used to obtain corneal swelling, and h umidified gas mixed with oxygen and nitrogen was used for corneal dehydrati on. First, in 6 young volunteers, we investigated the most suitable oxygen level for evaluating pump function by changing oxygen levels. Then, with th e optimal oxygen level, we attempted to evaluate pump function in 53 normal subjects, 5 Fuchs' dystrophy patients, and 3 iridocorneal endothelial synd rome (ICE) patients. Results: Swelling rate showed similar values regardless of age, but both de hydration rate and swelling rate plus dehydration rate decreased with aging . The swelling rate of 5 guttata corneas was significantly higher than that of age-matched control corneas. In contrast, dehydration rate markedly dec reased in guttata corneas, while the swelling rate plus dehydration rate of guttata corneas was comparable to that of age-matched corneas. In the 3 IC E corneas, however, swelling rate, dehydration rate, and swelling rate plus dehydration rate were markedly lower than those of both the fellow corneas and the age-matched control corneas. Conclusion: These observations lead us to conclude that in order to evaluat e pump function, it is necessary to monitor not only dehydration response f ollowing hypoxia but also swelling response under hypoxia. (C) 2000 Japanes e Ophthalmorogical Society.