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Distance PD is the separation between the visual axes of the eyes in their primary position, as the subject fixates on an infinitely distant object. [2] Near PD is the separation between the visual axes of the eyes, at the plane of the spectacle lenses, as the subject fixates on a near object at the intended working distance. [3]
The PD measuring instruments referred to as a pupillometers are optical devices that rest on the nose bridge similar to eyeglass frames and work by sighting the corneal reflection produced by an internally-mounted coaxial light source (e.g. Essilor Corneal Reflection Pupillometer [34]). These instruments are most commonly used for fitting ...
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Example of a Snellen-like depth test. Since the Howard-Dolman test described above is cumbersome, stereoacuity is usually measured using a stereogram in which separate panels are shown to each eye by superimposing them in a stereoscope using prisms or goggles with color or polarizing filters or alternating occlusion. [3]
The entrance pupil is the image of the aperture stop viewed from the front of the optical system and here it is a virtual image. Chief rays and marginal rays determine the location and the size of the entrance pupil, respectively. A camera lens adjusted for large and small aperture. The visible opening is the entrance pupil of the lens.
Telecanthus comes from the Greek word τῆλε (tele, "far") and the latinized form of the Greek word κάνθος, (kánthos, meaning 'corner of the eyelid'. Dystopia canthorum comes from the Greek δυσ - (dus-, “bad”) and τόπος (tópos, “place”) and the latinized Greek word κάνθος, adapted to latin morphology canthorum ("of the canthi").
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