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Fixation disparity. Fixation disparity is a tendency of the eyes to drift in the direction of the heterophoria. While the heterophoria refers to a fusion-free vergence state, the fixation disparity refers to a small misalignment of the visual axes when both eyes are open in an observer with normal fusion and binocular vision. [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 ( BSV) in the presence of increasing vergence demands. Motor fusion is largely accounted to ...
The strength of the prism is increased until the streak of the light passes through the centre of the prism, as the strength of the prism indicates the amount of deviation present. The Maddox rod is a handheld instrument composed of red parallel plano convex cylinder lens , which refracts light rays so that a point source of light is seen as a ...
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]
Armstrong wrote many books and articles on the subject of railroading and model railroading. His personal model railroad, the Canandaigua Southern, was the subject of many newspaper and magazine articles by other writers. In the late 1940s, Armstrong submitted a track plan to a contest sponsored by the magazine Model Railroader. His plan was so ...
On30 uses the American O scale of 1 ⁄ 4 inch to the foot, (ratio 1:48) to operate trains on HO gauge (16.5 mm / 0.65 in) track.The 30 indicates the scale/gauge combination is used to model 2 ft 6 in (762 mm) narrow gauge prototypes, although it is often used to model 2 ft (610 mm) and 3 ft (914 mm) gauge prototypes as well.
Athearn opened a separate facility in Hawthorne, California, in 1948, and that same year he branched into HO scale models for the first time. [1] Athearn acquired the Globe Models product line in 1951 and improved upon it, introducing a comprehensive array of locomotive, passenger, and freight car models. [2]
Exophoria. Exophoria is a form of heterophoria in which there is a tendency of the eyes to deviate outward. [1] During examination, when the eyes are dissociated, the visual axes will appear to diverge away from one another. [2] The axis deviation in exophoria is usually mild compared with that of exotropia .