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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 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.
Compound eye. A compound eye is a visual organ found in arthropods such as insects and crustaceans. It may consist of thousands of ommatidia, [1] which are tiny independent photoreception units that consist of a cornea, lens, and photoreceptor cells which distinguish brightness and color. The image perceived by this arthropod eye is a ...
Duochrome test. A duochrome test is a test commonly used to refine the final sphere in refraction (undercorrection and overcorrection), which makes use of the longitudinal chromatic aberration of the eye. Because of the chromatic aberration of the eye, the shorter wavelengths (green) are focused in front of the longer red wavelengths.
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 ...
Keratometer. A keratometer, also known as an ophthalmometer, is a diagnostic instrument for measuring the curvature of the anterior surface of the cornea, particularly for assessing the extent and axis of astigmatism. It was invented by the German physiologist Hermann von Helmholtz in 1851, although an earlier model was developed in 1796 by ...
The extraocular muscles, or extrinsic ocular muscles, are the seven extrinsic muscles of the eye in humans and other animals. [1] Six of the extraocular muscles, the four recti muscles, and the superior and inferior oblique muscles, control movement of the eye. The other muscle, the levator palpebrae superioris, controls eyelid elevation.
Central visual field. The Amsler grid, used since 1945, is a grid of horizontal and vertical lines used to monitor a person's central visual field. The grid was developed by Marc Amsler, a Swiss ophthalmologist. It is a diagnostic tool that aids in the detection of visual disturbances caused by changes in the retina, particularly the macula (e ...
It can be used to establish whether a patient has the ability for the eyes to fuse the light that is received from each eye into 4 lights. The test is indicated with the use of a presence of a prism in individuals with a strabismus and fusion is considered present if 4 lights are maintained, with or without the use of a prism. The W4LT can also ...
Cover test. A cover test or cover-uncover test is an objective determination of the presence and amount of ocular deviation. It is typically performed by orthoptists, ophthalmologists and optometrists during eye examinations . The two primary types of cover tests are: the alternating cover test. the unilateral cover test (or the cover-uncover ...