The Light Streak on Retinal Vessels

By ophthalmoscopy, a bright light streak is seen in the center of retinal vessels, and the intensity of this reflection (I r ) is found to be different for arteries and veins. Various physical parameters affect this reflection, and the present study analyses, on a theoretical basis, possible explanations of the variability of the light streak on different types of vessels. Parameters found to influence I r are the roughness of the surface of the blood column, the indices of refraction of erythrocytes and plasma, the size of the pupil, the axial length of the eye and the tilt of the blood vessel relative to the direction of incident light. Numerical analysis of a simplified model of retinal vessel geometry and blood flow enable us to present relations between relative intensity and the various parameters.