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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]
Convergence insufficiency. Convergence Insufficiency. Other names. Convergence disorder. Specialty. Ophthalmology, optometry. Convergence insufficiency is a sensory and neuromuscular anomaly of the binocular vision system, characterized by a reduced ability of the eyes to turn towards each other, or sustain convergence .
IPR is an irreversible procedure and can be an alternative to dental extraction. Indications for the procedure include mild to moderate crowding (4 - 8mm), [7] black triangles in anterior teeth, enhancing retention and stability after orthodontic treatment, and correction of the Curve of Spee.
Enamel prism. An enamel prism, or enamel rod, is the basic unit of tooth enamel. Measuring 3-6 μm in diameter in primates, [1] enamel prism are tightly packed hydroxyapatite crystals structures. The hydroxyapatite crystals are hexagonal in shape, providing rigidity to the prism and strengthening the enamel.
Post and core. A post and core crown is a type of dental restoration required where there is an inadequate amount of sound tooth tissue remaining to retain a conventional crown. A post is cemented into a prepared root canal, which retains a core restoration, which retains the final crown. [1] [2]
Prism adaptation. Prism adaptation is a sensory-motor adaptation that occurs after the visual field has been artificially shifted laterally or vertically. It was first introduced by Hermann von Helmholtz in late 19th-century Germany as supportive evidence for his perceptual learning theory (Helmholtz, 1909/1962). [1]
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]
Advantages and disadvantages. Advantages of air abrasion include that it preserves more healthy tooth tissue (which can increase the strength and longevity of restorations), and has less risk of fracturing or chipping a tooth when compared to a traditional pneumatic dental drill.
Dental compomers, also known as polyacid-modified resin composite, are used in dentistry as a filling material. They were introduced in the early 1990s as a hybrid of two other dental materials, dental composites and glass ionomer cement, in an effort to combine their desirable properties: aesthetics for dental composites (they are white and ...
Nance–Horan syndrome is a rare X-linked dominant syndrome characterized by congenital cataracts leading to profound vision loss, characteristic dysmorphic features, and dental anomalies. [1] [2] Microcornea, microphthalmia, and mild or moderate intellectual disability may accompany these features.