The form of the human pupil

Abstract

The purpose of this study was to characterize the form of the pupil in normal human subjects. Using a modified slitlamp, photographs of pupils were taken in steady illumination and 10-20 sec after darkness. Transparencies were projected and digitized, and the pupil margin was represented as a circular Fourier series. Best-fit ellipses were also determined. The placement of the pupil relative to the limbus was determined in a number of subjects. Results from 23 subjects indicated that in both darkness and light, average pupil noncircularity was 0.0166. (A value of 0.0200 is easy to detect with the unaided eye from the photographs.) On average, the best-fit ellipse accounted for about half of the noncircularity (59.6% in darkness; 47.7% in light). Most of the contribution to shape was made by the first 4 or 5 harmonics. Shapes were usually stable within a session and could remain fairly stable for at least a year; however, shapes for different subjects were not very similar, especially in the light. (Average pairwise similarity: 0.106 in darkness; 0.034 in light; similarity can have values from -1 to 1.) For a given subject, shapes in light and dark were often fairly similar (average similarity 0.260), but there were systematic differences: in eyes where the ellipse contributed > 20% of noncircularity, ellipse major axes clustered around vertical in darkness, and horizontal in light, implying greater contraction near the vertical meridian. Even pupils with little elliptical contribution turned out to contract more near the vertical meridian. There was some tendency for left and right eyes of an individual to show mirror symmetry of shape. In the dark, pupils were located 0.27 +/- 0.09 mm nasal and 0.20 +/- 0.15 mm superior to the limbus center, and usually moved slightly further nasal or superior in the light. Noncircularity increased with age (0.0015/decade). It was concluded that pupils show individuality of shape, with significant regularities within and across subjects.

Development of a Smartphone-based Pupillometer

“…Even if the infrared videography can also provide dynamic analysis including constriction velocity, most studies on pupil analysis in ophthalmology and neuroscience have still been focused on the variation of pupil size [15][16][17][18][19][20][21]. This is because the difference of pupil size (diameter or area) in response to PLR directly reflects the state of the autonomic nervous system resulting from both the sympathetic and parasympathetic influences that can be used for non-invasive diagnosis.…”

Higher-Order Wavefront Aberrations for Populations of Young Emmetropes and Myopes

“…But, as for Thibos et al's study, 4 a possible factor might be that their subject's pupil was dilated while we tested the natural pupil. After dilation, the pupil center could be shifted [31][32][33][34][35] and become closer to the line of sight. This shift of the pupil center toward the line of sight could make the structure of higher-order aberrations more symmetrical with respect to the line of sight, thus systematically reducing the values associated to the asymmetric higherorder aberrations of the population under study.…”

Wavefront Reconstruction from Slope Data Within Pupils of Arbitrary Shapes Using Iterative Fourier Transform

“…Also the fast Fourier transform makes wavefront reconstruction using the iterative Fourier technique faster than the SVD algorithm. Examples of noncircular pupils such as elliptical, annular, and hexagonal are given to cover practical applications of eyes with elliptical pupils [9] and telescopes with central obscuration [10] or with hexagonal mirrors [11]. An irregular pupil is also included in the study.…”