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Presbyopia is a typical part of the aging process. [4] It occurs due to age related changes in the lens (decreased elasticity and increased hardness) and ciliary muscle (decreased strength and ability to move the lens), causing the eye to focus right behind rather than on the retina when looking at close objects. [4]
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 .
Some cases of convergence insufficiency are successfully managed by prescription of eyeglasses, sometimes with therapeutic prisms. Pencil push-ups therapy is performed at home. The patient brings a pencil slowly to within 2–3 cm (0.79–1.18 in) of the eye just above the nose about fifteen minutes per day five times per week.
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]
Esophoria is an eye condition involving inward deviation of the eye, usually due to extra-ocular muscle imbalance. It is a type of heterophoria .
If the patient saw a red line to the left and white light to the right, they are said to have exotropia or exophoria (crossed diplopia) in which base in(BI) prisms of increasing strength are used until the lines are superimposed. Maddox rod test tutorial. Method for measuring vertical deviations: 1.
In quantum mechanics Thomas precession is a correction to the spin-orbit interaction, which takes into account the relativistic time dilation between the electron and the nucleus in hydrogenic atoms. Basically, it states that spinning objects precess when they accelerate in special relativity because Lorentz boosts do not commute with each other.
Ray transfer matrix analysis (also known as ABCD matrix analysis) is a mathematical form for performing ray tracing calculations in sufficiently simple problems which can be solved considering only paraxial rays. Each optical element (surface, interface, mirror, or beam travel) is described by a 2×2 ray transfer matrix which operates on a ...
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]
Plane polarized light: According to the wave theory of light, an ordinary ray of light is considered to be vibrating in all planes of right angles to the direction of its propagation. If this ordinary ray of light is passed through a nicol prism, the emergent ray has its vibration only in one plane.