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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 ...
Geometric dimensioning and tolerancing (GD&T) is a system for defining and communicating engineering tolerances via a symbolic language on engineering drawings and computer-generated 3D models that describes a physical object's nominal geometry and the permissible variation thereof. GD&T is used to define the nominal (theoretically perfect ...
Engineering tolerance is the permissible limit or limits of variation in: a physical dimension; a measured value or physical property of a material, manufactured object, system, or service; other measured values (such as temperature, humidity, etc.); in engineering and safety, a physical distance or space (tolerance), as in a truck (lorry ...
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]
Level (optical instrument) A level is an optical instrument used to establish or verify points in the same horizontal plane in a process known as levelling. It is used in conjunction with a levelling staff to establish the relative height or levels (the vertical separation) of objects or marks. It is widely used in surveying and construction to ...
Prism (geometry) In geometry, a prism is a polyhedron comprising an n-sided polygon base, a second base which is a translated copy (rigidly moved without rotation) of the first, and n other faces, necessarily all parallelograms, joining corresponding sides of the two bases. All cross-sections parallel to the bases are translations of the bases.
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 ]
Conversely, the range of cyclovergence-based cyclofusion can be trained using dove prisms that actively rotate the field of view: "The patient fixates a vertical line target, and the dove prism is rotated in the direction to increase the action of the insufficient muscle while fusion is maintained." [7]