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A dioptre (British spelling) or diopter (American spelling), symbol dpt, is a unit of measurement with dimension of reciprocal length, equivalent to one reciprocal metre, 1 dpt = 1 m −1. It is normally used to express the optical power of a lens or curved mirror , which is a physical quantity equal to the reciprocal of the focal length ...
Prentice's rule, named so after the optician Charles F. Prentice, is a formula used to determine the amount of induced prism in a lens: = where: P is the amount of prism correction (in prism dioptres) c is decentration (the distance between the pupil centre and the lens's optical centre, in millimetres)
Prism and Base Prism refers to a displacement of the image through the lens, often used to treat strabismus and other binocular vision disorders. The prism value is measured in prism diopters , and Base refers to the direction of displacement.
Four prism dioptre reflex test. Purpose. assess alignment of both eyes. The Four Prism Dioptre Reflex Test (also known as the 4 PRT, or 4 Prism Dioptre Base-out Test) is an objective, non-dissociative test used to prove the alignment of both eyes (i.e. the presence of binocular single vision) by assessing motor fusion. [1]
Amplitude of accommodation. The amplitude of accommodation is the maximum potential increase in optical power that an eye can achieve in adjusting its focus. It refers to a certain range of object distances for which the retinal image is as sharply focussed as possible. Amplitude of accommodation is measured during routine eye-examination.
Clinically, accommodative convergence is measured as a ratio of convergence, measured in prism diopters, to accommodation, measured in diopters of near demand. The patient is instructed to make a near target perfectly clear and their phoria is measured as the focusing demand on the eye is changed with lenses.
In 1909, Nathan Shigon of New York City invented a monocular optometer with a range of +0.25 to +6.00 diopters, consisting of a mechanism where a disc of low-powered lenses advanced a second disc of higher power lenses automatically with each rotation, as in a modern phoropter.
The prism cover test ( PCT) is an objective measurement and the gold standard in measuring strabismus, i.e. ocular misalignment, or a deviation of the eye. [1] It is used by ophthalmologists and orthoptists in order to measure the vertical and horizontal deviation and includes both manifest and latent components. [1]
In optics, optical power (also referred to as dioptric power, refractive power, focusing power, or convergence power) is the degree to which a lens, mirror, or other optical system converges or diverges light. It is equal to the reciprocal of the focal length of the device: P = 1/f. [1]
Dioptrics. Dioptrics is the branch of optics dealing with refraction, especially by lenses. In contrast, the branch dealing with mirrors is known as catoptrics. [1] Telescopes that create their image with an objective that is a convex lens ( refractors) are said to be "dioptric" telescopes. An early study of dioptrics was conducted by Ptolemy ...