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R. Montes-Mico, V. Fernandez-Sanchez, S. Bonaque, N. Lopez-Gil; Does Pupil Miosis Modify the Optics of the Human Eye?. Invest. Ophthalmol. Vis. Sci. 2007;48(13):5628.
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It is known that in some animal species, such us avians, pupil miosis increases the curvature of the first surface of the lens increasing its power and consequently providing certain accommodation. With a simple experiment we analyzed if this fact happens also in the human eye.
We measured the ocular aberrations in 26 eyes (subjects ranging in age from 20 to 40 years) using an Irx3 aberrometer (Imagine Eyes, France) under natural viewing conditions. The measured eyes fixated to a dim target (2 cd/m2) while the counterpart eye was either occluded (so the measured eye showed a large pupil) or highly illuminated with a white lamp (so the measured eye showed a small pupil). Then, Zernike values obtained in both situations were compared within the same pupil diameter corresponding to the one obtained under the high illumination condition. The experiment was performed fist with the unaccommodated eye and then with the eye accommodating to a stimulus of 3 D closer to its far point.
Although the changes of aberrations depend on the subject and were small due to the small pupil diameter, we have noted significant variation in some aberration coefficients for the two accommodation states between both illumination conditions. Specially, spherical aberration (SA) increased significantly after pupil miosis (p = 0.0017 and 0.0021 for 0 and 3D of accommodation, respectively). The mean increase of SA measured was 0.018 and 0.027 microns for 0 and 3D of accommodation, respectively, for a 3-mm pupil (which would represent 0.14 and 0.21 microns for a 5-mm pupil). Mean values of other ocular aberrations also vary significantly after pupil miosis (changes were larger than the standard deviation of the repeated measurements)
Besides the optical change produced by a decrease in the entrance pupil, pupil miosis slightly modifies the optics of the lens altering its SA. These optical changes could slightly modify the accommodation response
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