Calculations are experimentally verified employing 5 organic ophthalmic lenses of ☖ ±4 and 0.12 dioptres and 2 glass plane parallel plates 1.95 and 6.6 mm thick. Three effects are considered, pupil size variation of the system with and without lens lateral shifts of rays transmitted through the lens and reflections at the lens. In this paper, considering spherical standard ophthalmic lenses and defining the relative illuminance, Er, as the quotient between the illuminance at the cornea with and without lens, a methodology to evaluate Er in terms of easily determined parameters is developed. To study the influence of glare on the visual performance of a subject wearing an ophthalmic lens, it is useful to know how the lens affects the illuminance reaching the eye. We propose the use of this formula to estimate in a simple and approximate way the effective eccentricity angle corresponding to a far or near point source and to any standard ophthalmic lens and habitual vertex distance. To avoid these drawbacks, in the present article we obtain a formula for the mean visual magnification of a standard ophthalmic lens of spherical surfaces as a function only of its power. In the first case, the calculation requires data (not always available) concerning source location, lens construction parameters and vertex distance while, in the second, results are imprecise for thick lenses employed by patients suffering severe hyperopia. Under paraxial approximation, the lens visual magnification (quotient between the angles subtended at the corneal vertex by the point and by its image through the lens) can be evaluated as usual, either considering thick or thin lens. When a myopic or hyperopic eye wearing an ophthalmic lens looks at a stimulus and also receives light from a peripheral point, the lens modifies the eccentricity angle with which light originated at this point reaches the eye. Systems which are of interest for our Group and to verify the adequate performance ofīlick and acquire insights concerning its potential improvements. This enables us both to investigate some topics regarding the visual and mental Using Blick, weĬapture the right eye of six subjects and analyse the corresponding pupil and eye gaze Visual preferences, cognitive tasks, and writing via eye movements. We outlineĮach of the image processing steps required to determine pupil diameter and gazeįinally, we design and carry out five tests: visual acuity, homographic calibration, Then we explain how we develop Blick, first its illumination and detection systemĪnd then its software programmed in C++ using OpenCV and cvblob libraries. Moreover we deal with some concepts related to the traditional visual acuity test, usedįor eye control and refractive correction prescription (ophthalmic and contact lenses). Gical systems, its performance under different conditions and, in particular, its pupil. To pupil dilation and contraction or changes in gaze direction and, also, many otherĪfterwards we briefly describe the visual system, including its optical and neurolo. Processing of ocular images behaviours of the visual and/or mental systems associated To help us achieve these objectives, we review the state-of-the-artĬoncerning commercial and academic pupillometers and eye trackers the capture and Our goals are, first, to develop a low cost pupillometer eye tracker exhibiting anĪdequate performance and, second, to attain pupil diameter and gaze directión dataĭuring psychophysical tests and analyze information concerning certain visual and Or of other type), to study marketing conveniences of certain products, as a humanĬomputer interaction system (HCI) for people with motor disabilities, etc. This is, the device couldīe used to detect conscious or unconscious processes, to analyze preferences (sexual Mental resources employed when performing certain tasks. Blick could be used in variousĪpplications related not only to psychophysical vision tests but also to the study of Ophthalmic and psychological clinics or by any person. (UBA) in investigations dealing with the eye and, also, by other research groups, in This development is aimed to be used by the Grupo de Óptica y Visión Blick captures eye images, processes themīy means of real time computations and supplies plots and tables of pupil diameter and On a table) and runs in a Linux environment. (this meaning that the detection system and the subject’s chin rest are both mounted In a USB camera, an optical system and a filter). (consisting in two LEDs that emit infrared radiation) and a detection system (consisting The hardware comprises an illumination system In this Thesis we develop both the hardware and the software of a pupillometer eye
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