Intraocular humidity immediately after fluid-air exchange in pars plana vitrectomy

To study vitreous cavity humidity during fluid-air exchange in pars plana vitrectomy. Intraocular humidity in the vitreous cavity was recorded for 2 min in six artificial eyes, six enucleated pig eyes, and ten patient eyes, after the eyes had been filled with either humidified air (75% humidity) or dry air (8% humidity). In artificial eyes the humidity levelled off at a value that was approximately equal to the humidity of the infused air, i.e., a mean of 71.9% when humidified air was used and a mean of 14.4% when dry air was used. In enucleated pig eyes humidity increased slightly with humidified air and remained stable with dry air. In patients intraocular humidity increased to over 90%, regardless of whether humidified or dry air was used. In the living eye, dry air deprives the retinal tissue of humidity, which is lost into the vitreous cavity. This effect can be reduced by using humidified air.