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Prentice's rule is a formula to calculate the amount of prism correction in a lens based on decentration and lens power. It can be used for prescribing, tolerance control, or determining unprescribed prism in eyeglasses.
A fixation disparity is not constant within a certain observer, but can vary depending on the viewing conditions. If test prisms with increasing amount are placed in front of the observer’s eyes, the fixation disparity changes in the eso direction with base-in prisms and in the exo direction with base-out prisms (Fig. 3). These prisms force ...
The prism cover test (PCT) is an objective method to measure ocular misalignment or deviation of the eye. It involves using prism bars, occluder, and targets to neutralise the deviation and record the angle and base of the prism.
The prism fusion range (PFR) or fusional vergence amplitude is a clinical eye test performed by orthoptists, optometrists, and ophthalmologists to assess motor fusion, specifically the extent to which a patient can maintain binocular single vision in the presence of increasing vergence demands.
Dissociated vertical deviation (DVD) is an eye condition that causes one eye to drift upward spontaneously or after being covered. It is often associated with squints and can be diagnosed and treated by ophthalmologists.
Exophoria is a tendency of the eyes to deviate outward, usually mild and with fusion possible. It can be caused by refractive errors, divergence excess, or convergence insufficiency, and is common in infancy and childhood.
Learn about the different types of optical prisms, such as dispersive, reflective, beam-splitting and polarizing prisms, and how they refract, reflect or split light. Find out how prisms are made of transparent materials like glass, acrylic or fluorite, and how they can create spectra, images or polarizations.
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]