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Prism dioptres. Prism correction is commonly specified in prism dioptres, a unit of angular measurement that is loosely related to the dioptre. Prism dioptres are represented by the Greek symbol delta (Δ) in superscript. A prism of power 1 Δ would produce 1 unit of displacement for an object held 100 units from the prism. [2]
Esotropia is a form of strabismus in which one or both eyes turn inward. The condition can be constantly present, or occur intermittently, and can give the affected individual a "cross-eyed" appearance. [1] It is the opposite of exotropia and usually involves more severe axis deviation than esophoria. Esotropia is sometimes erroneously called ...
Incomitant strabismus cannot be fully corrected by prism glasses, because the eyes would require different degrees of prismatic correction dependent on the direction of the gaze. Incomitant strabismus of the eso- or exo-type are classified as "alphabet patterns": they are denoted as A- or V- or more rarely λ -, Y- or X-pattern depending on the ...
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]
Esophoria is an eye condition involving inward deviation of the eye, usually due to extra-ocular muscle imbalance. It is a type of heterophoria. Cause. Causes include: Refractive errors; Divergence insufficiency; Convergence excess; this can be due to nerve, muscle, congenital or mechanical anomalies.
Prism (optics) An optical prism is a transparent optical element with flat, polished surfaces that are designed to refract light. At least one surface must be angled — elements with two parallel surfaces are not prisms. The most familiar type of optical prism is the triangular prism, which has a triangular base and rectangular sides.
A prism compressor is an optical device used to shorten the duration of a positively chirped ultrashort laser pulse by giving different wavelength components a different time delay. It typically consists of two prisms and a mirror. Figure 1 shows the construction of such a compressor. Although the dispersion of the prism material causes ...
A Nicol prism is a type of polarizer. It is an optical device made from calcite crystal used to convert ordinary light into plane polarized light . It is made in such a way that it eliminates one of the rays by total internal reflection , i.e. the ordinary ray is eliminated and only the extraordinary ray is transmitted through the prism .
Ophthalmology. In ophthalmology, horror fusionis is a condition in which the eyes have an unsteady deviation, with the extraocular muscles performing spasm-like movements that continuously shift the eyes away from the position in which they would be directed to the same point in space, giving rise to diplopia. Even when the double vision images ...
The laser flash analysis or laser flash method is used to measure thermal diffusivity of a variety of different materials. An energy pulse heats one side of a plane-parallel sample and the resulting time dependent temperature rise on the backside due to the energy input is detected. The higher the thermal diffusivity of the sample, the faster ...