Abstract

The constriction of retinal vessels occurring in response to breathing 100% oxygen was studied in 10 normal subjects over a period of 30 min. Brachial blood pressure, radial pulse and end tidal CO₂ were recorded throughout. The mean arteriolar constriction was 15·3%±4·6 and venous constriction 21·8%±4·3. Time constants (the time for 95% of the maximal response to have occurred) were 2·25 min±0·75 and 2·37 min±0·57 for arterioles and veins respectively. A highly variable late vascular response was recorded. A small proportion of arterial vessels showing a response were nonuniform while a larger proportion of veins showed a significant dilatation.

Author Keywords: hyperoxia; retina; calibre; image analysis

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