Film: 9262

Medicine | 1950 | Silent | B/W

Clip:

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Synopsis:

Photograph of retinal vessels of kitten, having been injected with Indian ink. Photograph of regressive retinal vessels of kitten's litter mate, the result of high ambient oxygen pressure. Anaesthetic injection into abdomen of kitten. Metal retaining ring sutured onto kitten's cornea. Removal of anterior ocular structures, insertion of glass plate to retain the vitreous. Components of limbal window are demonstrated. Animal is enclosed in transparent plastic box for control of oxygen concentration. Box placed under microscope. Shot of retinal vessels through microscope. Scientist looks through microscope. Graphs to show effect on retinal vessels of exposure to high oxygen (90%) concentration. Time lapse photography through microscope to show closing of vessels with time. Similar shot involving vessels of a more mature animal. Dagram to show closing of vessels with time. Shot of vessels through microscope. Diagram to show various reactions of retinal vessels to oxygen. Illustrations of vessels.
[Summary] - Aetiological studies on retrolental fibroplasia have shown that obliteration of the retinal vessels by high ambient oxygen concentrations is the primary cause of the disease. This was first shown in the retina of the kitten by injection techniques and the film opens with a sequence showing reinae injected with Indian Ink demonstrating the differences between normal and oxygen-treated specimens. To study these phenomena in the living animal however, a new technique was devised which permits direct observation of the living retinal vessels in situ. The film goes on to how details of this method, which involves the removal of the anterior ocular structures and the insertion of a plane glass "limbal window" in their place. The retinal vessels can then be visualised by incident light microscopy and the ambient oxygen concentration varied by enclosing the animal in transparent plastic box connected to a source of oxygen supply.
On exposure to ambient hyperoxia, two effects are seen: 1- an immediate and transient closure occurring within five minutes, and 2- a delayed and permanent closure occurring within eight hours. The film continues with live sequences taken through the "limbal window" demonstrating the response of the vessels both to hyperoxia alone and also to intermittent air and hyperoxia. Diagrams are then shown, indicating the correlation between maturity and the degree of vaso-obliteraion, and also the order in which the vessels close. These effects are then summarised.
The final part of the film is concerned with the retinal vaso-proliferation which follows prolonged oxygen-incluced vessel closure. This is shown by means of diagrams together with photographs of injected specimens, and demonstrates that the abnormal neo-vascularisation is random and profuse and extends not only throughout the retina but also through the inner limiting membrane into the vitreous. It is suggested that the proliferation is related to the circumstances of oxygen lack which prevail in the oxygen-treated retina.


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