About Kai Schreiber Expertise Mostly questions specific to vision science and eye movements, with some expertise in general neuroscience and cognitive science. Strongest background in mathematical theory, modelling and the theory of perception, but I will try to answer anything that comes my way.
Experience Postdoc in Vision/Oculomotor research.
Organizations UC Berkeley
Publications Journal of Vision, Nature, IEEE Transactions on Biomedical Enginerring
Education/Credentials Dipl Phys (Universtität Tübingen), PhD (Physiology, Univeristy of Toronto), Graduate Program in Neuroscience (University of Toronto)
Expert: Kai Schreiber Date: 11/26/2007 Subject: Pupil Dilation
Question What would be reasons for both pupils to dilate and constrict very rapidly, going from their normal size to very large then back to normal within seconds? And, not just once but over and over. There are no medications or illegal drugs being used. The lighting will remain the same, no lights being turned on or off. Also, I've kind of noticed they will be large while focusing then when the eyes shift they shrink very fast then begin dilating again.
Answer Hi Phillip,
constriction of the pupil, called Miosis, can be caused by natural mechanisms, drugs or can be a sign of disease. A short overview is given at Wikipedia (http://en.wikipedia.org/wiki/Miosis), for example.
Constriction of the pupil in natural conditions will often be caused by an increase in lighting, but there is a second beneficial effect of a small pupil that's exploited by the visual system: a small pupil, like a small aperture in photography, will increase depth of focus. So when the lens becomes less flexible with age, part of its function is taken over by pupillary constriction. Similarly, when the eye is redirected to a new target, focus might have to change, and initial pupil constriction might help maintain focus even when the lens can't keep up.
Without having seen the actual constriction, it's hard to say anything more specific. If you think the constriction looks very unusual, you might want to show it to an ophthalmologist.
