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Purpose. measuring strabismus. 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]
The most common application for this is the treatment of strabismus. By moving the image in front of the deviated eye, double vision can be avoided and comfortable binocular vision can be achieved. Other applications include yoked prism where the image is shifted an equal amount in each eye.
Prisms: to measure the degree of squints; in other instruments; refractive correction; etc. Placido's disc: to assess the condition of the corneal surface Retinoscope: objective determination of refractive error and for looking inside the eye Loupe: used to search for magnified examination of the anterior segment of the eye (uniocular or binocular)
Aberrations of the eye. The eye, like any other optical system, suffers from a number of specific optical aberrations. The optical quality of the eye is limited by optical aberrations, diffraction and scatter. [1] Correction of spherocylindrical refractive errors has been possible for nearly two centuries following Airy's development of methods ...
The Eye-Level and AE Finders are the basic eye-level prism finders, similar to most other SLR systems' prism finders. Both include a hot shoe for on-camera flash, or attachments to remotely trigger the shutter.
In optics, chromatic aberration ( CA ), also called chromatic distortion and spherochromatism, is a failure of a lens to focus all colors to the same point. [1] It is caused by dispersion: the refractive index of the lens elements varies with the wavelength of light. The refractive index of most transparent materials decreases with increasing ...
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.
The Prentice position is an orientation of a prism, used in optics, optometry and ophthalmology. In this position, named after the optician Charles F. Prentice, the prism is oriented such that light enters it at an angle of 90° to the first surface, so that the beam does not refract at that surface. All the deviation caused by the prism takes ...
Eye glasses with an included prism power is the optical method to reduce a fixation disparity. Different procedures have been proposed to determine the required amount of prism for the individual. Based on prism-FD curves (Fig. 3b), one can find the aligning prism sP 0 that nullifies the naturally prevailing fixation disparity sFD 0. This test ...
A corrective lens is a transmissive optical device that is worn on the eye to improve visual perception. The most common use is to treat refractive errors: myopia, hypermetropia, astigmatism, and presbyopia. Glasses or "spectacles" are worn on the face a short distance in front of the eye.