The hydration of the cornea

Abstract

The swelling of the cornea in the excised rabbit eye was studied with a view to establishing whether, in the living eye, there is an active-transport mechanism that normally prevents the uptake of aqueous humour, tears, and limbal capillary filtrate. The following results are described: (a) The corneae of eyes maintained for 16 hours at 31[degree] are far less heavily hydrated than those maintained at 7[degree], in fact half of the eyes kept at 31[degree] had a hydration within the normal range, (b) Subsequent keeping of eyes at 31[degree], after maintaining them at 7[degree] for 16 hours, causes a reversal of the hydration that takes place at the lower temperature, (c) Removal of the epithelium causes the hydration to increase at 31[degree] but has a very small effect at 7[degree]. The hydration of corneae maintained without epithelium at 31[degree] is less than that of intact corneae at 7[degree], indicating that the endothelium resists the uptake of fluid, (d) The state of hydration is apparently independent of the rate of evaporation from the eye. (e) Anoxia causes a very marked increase in hydration. All the results are consistent with the existence of an active-transport mechanism but quite inconsistent with the view that the hydration in vivo is prevented by an osmotic withdrawal of fluid into the supposedly hypertonic tears and aqueous humour.