Experimental physiology / by Sir Edward Sharpey-Schafer.

  • Edward Albert Sharpey-Schäfer
Date:
1927
Catalogue details

Licence: In copyright

Credit: Experimental physiology / by Sir Edward Sharpey-Schafer. Source: Wellcome Collection.

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    nearer the eye, irregular fibre-like markings can be seen in the spot of light which corresponds to the pupil; these markings are caused by the fibres of the lens. If the biconcave lens is approached to within a few centimeters of the eye, the markings disappear and become replaced by irregularly moving spots; these are due to floating cells in the anterior part of the vitreous. Instead of a biconcave lens, an ordinary microscope, the field of which is evenly illuminated, may be used. The observer looks into the eyepiece from a distance of about 20 cm.; under these circum- stances he will see in the eyepiece the pupil as a circular spot of light, surrounded by the serrated margin of the iris. As the eye of the observer is brought nearer to the eyepiece the spot of light becomes larger until, at a point about 5 cm. away, the fibre-like structure of the lens appears. If the eye is brought still closer, vitreous “ floaters ” can be seen moving across the illuminated field. The part of the vitreous lying immediately in front of the retina can be inspected by looking at an evenly illuminated surface, such as a bright but cloudy sky. Numerous irregular spots and threads will appear moving across the field of vision; these are due to tissue elements in the vitreous humor. They are the well known muscat volitantes.
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