Search results
Results from the WOW.Com Content Network
Esophoria is an eye condition involving inward deviation of the eye, usually due to extra-ocular muscle imbalance. It is a type of heterophoria. Cause. Causes include: Refractive errors; Divergence insufficiency; Convergence excess; this can be due to nerve, muscle, congenital or mechanical anomalies.
Heterophoria is the misalignment of the visual axis such that one or both eyes are not properly fixated to an object of interest. When the visual axis is misaligned in such a way, it is corrected by the fusional vergence system. Diagnosis. The cross-cover test, or alternating cover test is usually employed to detect heterophoria.
The test is indicated with the use of a presence of a prism in individuals with a strabismus and fusion is considered present if 4 lights are maintained, with or without the use of a prism. The W4LT can also be indicated when aiding a person to develop and strengthen their fusional capacities.
Maddox wing. The Maddox Wing is an instrument utilized by ophthalmologists, orthoptists and optometrists in the measurement of strabismus (misalignment of the eyes; commonly referred to as a squint or lazy eye by the lay person). It is a quantitative and subjective method of measuring the size of a strabismic deviation by dissociation of the ...
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 .
Cyclotropia cannot be corrected with prism spectacles in the way other eye position disorders are corrected. (Nonetheless two Dove prisms can be employed to rotate the visual field in experimental settings.) For cyclodeviations above 5 degrees, surgery has normally been recommended.
Fourth cranial nerve palsy or trochlear nerve palsy, is a condition affecting cranial nerve 4 (IV), [1] the trochlear nerve, which is one of the cranial nerves. It causes weakness or paralysis of the superior oblique muscle that it innervates. This condition often causes vertical or near vertical double vision as the weakened muscle prevents ...
A double Porro prism system reflects light four times. Porro prisms are most often used in pairs, forming a double Porro prism. A second prism rotated 90° with respect to the first, is placed such that light will traverse both prisms. The net effect of the prism system is a beam parallel to but displaced from its original direction, with the ...
An Uppendahl prism is an erecting prism, i.e. a special reflection prism that is used to invert an image (rotation by 180°). The erecting system consists of three partial prisms made of optical glass with a high refractive index cemented together to form a symmetric assembly and is used in microscopy as well as in binoculars technology.
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]