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Claus Nissen, Birgit Sander, Henrik Lund-Andersen; The Pupil Size In Pupillometry. To Dilate Or Not To Dilate. Invest. Ophthalmol. Vis. Sci. 2012;53(14):144.
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To evaluate the influence of the size of the light exposed pupil in one eye on the pupillary light response of the other eye.
Using a monochromatic pupillometer, the left eye in each of ten healthy subjects was exposed to 20 seconds of monochromatic light of luminance 300 candela per square meter, first red, 660 nanometer and in a following session, blue, 470 nanometer.The consensual pupillary contraction in the right eye was measured simultaneusly before, during and after light exposure. Tropicamide one percent or pilocarpine two percent was subsequently instilled into the left eye and when the eye was either maximally dilated or contracted, the entire sequence was repeated. The AUC, Area Under the Curve, that is the integral of contraction versus time, in the right eye was calculated for each individual sequence.
Prior dilatation of the left pupil augmented the post light contraction to blue, p less than 0.0001, but not to red light. The contraction during light exposure did not change. Prior contraction of the left pupil decreased the post-stimulus contraction to blue light, p less than 0.04, but not to red light.
The size of the light exposed pupil influences the magnitude of the response to blue, but not to red light. Thus prior dilatation may prove useful, when the response to blue light, as a marker of melanopsin containing retinal ganglion cell function, is of interest, especially when this response is weak. Prior dilation may also be useful as a way of exchanging long duration of stimulus for short duration, thus making the examination faster, less prone to artefacts and not least, less tiresome to the patient.
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