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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 .
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 test).
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 ( BSV) in the presence of increasing vergence demands. Motor fusion is largely accounted to ...
A prism of power 1 Δ would produce 1 unit of displacement for an object held 100 units from the prism. Thus a prism of 1 Δ would produce 1 cm visible displacement at 100 cm, or 1 metre. This can be represented mathematically as: = where is the amount of prism correction in prism dioptres, and is the angle of deviation of the light.
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]
x, s, d, u, x 1, s 1, d 1, u 1: m [L] Image distance x', s', d', v, x 2, s 2, d 2, v 2: m [L] Object height y, h, y 1, h 1: m [L] Image height y', h', H, y 2, h 2, H 2: m [L] Angle subtended by object θ, θ o, θ 1: rad dimensionless Angle subtended by image θ', θ i, θ 2: rad dimensionless Curvature radius of lens/mirror r, R: m [L] Focal ...
Accounting for two states of spin, each n-shell can accommodate up to 2n 2 electrons. In a simplistic one-electron model described below, the total energy of an electron is a negative inverse quadratic function of the principal quantum number n, leading to degenerate energy levels for each n > 1.