Efects of Anoxia on the Fluorescein

IT was demonstrated by Giardini and Nizetic (1949), using the Amsler-Huber fluorescein test (1949), that when guinea-pigs are made to breathe air containing approximately 5.52 to 4.16 per cent. oxygen (corresponding to the atmosphere at an altitude of 10-12,000 metres, or 35,000-70,000 feet) for one hour, there is an increase in the concentration of the fluorescein in the anterior chamber. When the fluoresceil test was performed on animals which had first breathed a reduced oxygen concentration and had then breathed normal air for half an hour, it was found that these changes were reversible, and that the fluorescein curve again became normal. For technical reasons these workers were not able to investigate the behaviour of the blood-aqueous barrier during anoxia since their technique entailed such a degree of oxygen-deficiency that serious general disturbances were produced in the experimental animals. In this series of experiments these difficulties have been overcome by the use of an apparatus with which the fluorescein test could be performed during anoxia of the medium-severe type. Cats were used instead of guinea-pigs, partly because the anatomy and physiology ofthe cat's eye are regarded as being nearer to those of the human eye, and partly because it is possible to inject the fluorescein intravenously in this animal and thus to obtain approximately the same concentration of fluorescein in the blood in all cases.