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12 October 2001

How to Observe Blood Flow in Your Eye

by C. L. Stong and Shawn Carlson

Adapted from "The Amateur Scientist," October, 1969

Figure 1. (Click image to enlarge)

Julio Santilli of Long Island City, N.Y. conceived of an extremely elegant method to examine the blood in his own capillaries while shaving Santilli writes "I noticed that the capillaries in the white of my eye are covered with transparent tissue, and I wondered what the blood would look like if I could see it up close. The question itself suggested the kind of instrument I would need: an optically folded microscope. Light from the capillaries of one eye would pass through the objective lens of a microscope and proceed to a distant mirror for reflection to the other eye [Figure 1]. I had a 10-power objective lens and a 10-power eyepiece." A front silvered mirror works best, but a regular mirror will also work except that the experimenter might have to contend with a faint double image that arises from the reflection from the glass cover. [NOTE: Front surface mirrors can easily be made by breaking the housing off a plastic toy makeup mirror and dissolving the backing with a general solvent like Methyl Ethyl Ketone. SC]

All parts of the system, including the viewer's head, must be rigidly supported because all motions of any part are equally magnified. In Santilli's design the objective lens, the eyepiece and the mirror are supported by a wooden box. The box rests on and is attached to the upper end of a lens barrel from an old portrait camera. The barrel has a rack and pinion that serve as a focusing adjustment. The framework holding the lens barrel is made of wood and includes both a head board and a bite board [see Figure 2 ]. These rests are essential. "Indeed, I have been tempted at times to strap my skull to the fixture" says Santilli.

Figure 2. (Click image to enlarge)

Neither the dimensions nor the arrangement of the parts is critical. Focusing can be accomplished by moving the entire optical system up or down, as in the design shown, or by moving the objective lens alone. Santilli lights the capillaries with a homemade spot lamp, and regulates the brightness with a rheostat. Use minimum light to prevent irritation or damage to the eye, and limit periods of observation to five minutes, with an hour or two of rest between periods.

Say's Santilli "What does one see? This depends on the size of the capillaries. I classify the capillaries simply as large, medium and small. The large ones show no flow of blood because the stream is thick and consequently opaque, nor is regular flow observed in the smallest capillaries. Single cells or small clusters of cells spurt irregularly through the smallest capillaries much as random tracks appear in a Wilson cloud chamber. The most interesting flows are found in capillaries of medium size, which are both clearly transparent and supplied with just enough blood to display the streaming red cells to advantage.

"I found viewing my own blood a fascinating experience. Here and there the cells move in synchronism with the pulse, alternately speeding up and slowing down, but the action of the heart is not apparent in all capillaries. In man the flow is constant. Occasionally the blood comes to a complete halt and then resumes in the same direction. Most astonishing are times when the cells stop and reverse direction against the powerful pumping of the heart. Another stop follows, and then the flow resumes in the original direction. Rarest of all are occasions when a capillary empties. This usually occurs during a backflow, when for some reason the blood supply appears to be cut off. The capillary seems to vanish, but it reappears in a matter of seconds with the return of normal circulation.

"Several experiments come to mind. For example, it might be interesting to observe the effects of coffee, tea, beer or tobacco on the circulation. It should also be possible to investigate the influence of aging on the structure of certain capillaries and on the circulation. Such changes could be photographed by fitting the eyepiece with an optical beam splitter to divert part of the light into a camera. The apparatus would similarly lend itself to recording the effects of emotional or mental states on the circulatory system."