A fiber optic point-source was designed for in vivo measurement of light transmission and scattering. The point-source consists of an optical fiber, with a core diameter of about 8 um, mounted in a stainless steel cannula. At the tip of the cannula the entrance face of a 1 mm micro prism is fixed. The hypotenuse face of the prism is coated with aluminum and acts as a mirror reflecting the light out through the exit face. The arrangement allows light fed into the optical fiber to be emitted in a direction perpendicular to the axis of the cannula. The cannula is bent to allow its in vivo introduction into the eye at the posterior pole. The prism is positioned close to the retina along the optical axis of the eye. The light is transmitted through the eye in a reversed beam path (from vitreous towards cornea). In the vitreous, the light source emits within a numerical aperture of about 0. 1 allowing the exiting light to be well confined through the dilated pupil. After careful calibration of the light source, accurate measurements can easily be performed by positioning detector equipment outside the eye. The small size of the point-source (in the range of the eye's resolution) allows measurement of light scatter at both wide and narrow angles. With this intraocular fiber optic technique, it is possible to perform several types of experiments, including measurements of light transmission and scattering, and also studies of fluorescence phenomena in different parts of the ocular media.