Fig. 1. Variation in intraocular oxygen partial pressure (P_O) during embryonic development and following treatment with 50% O₂. An optode was used to measure P_O in the anterior vitreous (open symbols) and mid-vitreous (filled symbols) of normoxic chicken embryos (circles). Some embryos were incubated from E7 to E13 in an atmosphere of 50% O₂:50% N₂. Measurements made on those embryos (triangles), at E13, indicated that hyperoxia results in a significant increase in P_O in both the anterior and mid-vitreous.