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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 (BSV) in the presence of increasing vergence demands. Motor fusion is largely accounted to ...
In geometrical optics, vergence describes the curvature of optical wavefronts. [1] Vergence is defined as. where n is the medium's refractive index and r is the distance from the point source to the wavefront. Vergence is measured in units of dioptres (D) which are equivalent to m −1. [1] This describes the vergence in terms of optical power.
Near point of convergence or no previous correction NRC Normal retinal correspondence NV Near vision NWT Normal wearing time o symptoms Zero symptoms ϕ Horizontal orthophoria θ Vertical orthophoria ⊕ Horizontal and vertical orthophoria OC's Optical centres Occ. Occupation OD oculus dexter (right eye) OH Ocular history OMB Oculo motor balance
The Brock string is commonly employed during treatment of convergence insufficiency and other anomalies of binocular vision. It is used to develop skills of convergence as well as to disrupt suppression of one of the eyes. [ 1 ] During therapy, the one end of the Brock string is held on the tip of the nose while the other is tied to a fixed point.
Prism (optics) A familiar dispersive prism. 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 ...
Dispersive prism. In optics, a dispersive prism is an optical prism that is used to disperse light, that is, to separate light into its spectral components (the colors of the rainbow). Different wavelengths (colors) of light will be deflected by the prism at different angles. [1] This is a result of the prism material's index of refraction ...
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]
Although glasses and/or patching therapy, exercises, or prisms may reduce or help control the outward-turning eye in some children, surgery is often required. A common form of exotropia is known as "convergence insufficiency" that responds well to orthoptic vision therapy including exercises. This disorder is characterized by an inability of ...