Seeing patterns
Why do we see patterns in light and this is so even when we close our eyes?
R. SUJITHA, Chennai
Basic working of the eye is as follows — Focusing mechanism of the eye, namely, cornea and lens focus the image of the object being seen on to the retina. Retina is a nerve tissue which reacts by absorbing the focused light [energy] and converting it into electrical impulses which travel through the optic nerve reaching the brain resulting in visual perception.
Any electric discharge from the retina will be “seen” as a visual perception. Retina can spontaneously discharge electrical impulses under several situations. The most common will be small changes in pressure of the eye which can occur with tight closing of the lids, rubbing of the eye, holding the breath and straining hard, a blow to the eye etc.
These induced pressure changes will cause the retina to discharge electrical impulses resulting in a perception of patterns of light. This phenomenon is known as ‘phospenes.’ These can typically be seen when the eyes are closed.
When one looks at a clear background particularly a light blue back ground [as in the open clear sky] we can observe certain patterns or designs in form of lines dots etc moving with the movement of the eyes. These are ‘vitreous floaters.’
Vitreous body is a gel like substance filling the posterior portion of the eye. This gel sometimes has particles which are visible to us under conditions mentioned. Over and above these phenomena, under very ideal conditions, against a clear blue back-ground one can actually see the blood flowing through the retinal capillaries.
The network of capillaries can be made out as well as the white blood cell flowing through them will be perceived as very tiny luminous white dots moving around. All of the above can be classified as ‘entoptic phenomena.’
Dr. ARULMOZHI VARMAN, Uma Eye Clinic, Chennai
