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The Four Prism Dioptre Reflex Test (also known as the 4 PRT, or 4 Prism Dioptre Base-out Test) is an objective, non-dissociative test used to prove the alignment of both eyes (i.e. the presence of binocular single vision) by assessing motor fusion.
- BD: base down prisms - BU: base up prisms - BO: base out prisms - BI: base in prisms - eso: esotropia - exo: exotropias - L/R: left hypertropia or right hypotropia - R/L: right hypertropia or left hypotropia Double Maddox rod test. The double Maddox rod test can also be used to assess torsion and measure cyclotropias.
Monofixation syndrome ( MFS) (also: microtropia or microstrabismus) is an eye condition defined by less-than-perfect binocular vision. [1] It is defined by a small angle deviation with suppression of the deviated eye and the presence of binocular peripheral fusion. [2] That is, MFS implies peripheral fusion without central fusion.
Treatment options for esotropia include glasses to correct refractive errors (see accommodative esotropia below), the use of prisms, orthoptic exercises, or eye muscle surgery. The term is from Greek eso meaning "inward" and trope meaning "a turning".
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.
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]
Dissociated vertical deviation. Dissociated vertical deviation ( DVD) is an eye condition which occurs in association with a squint, typically infantile esotropia. The exact cause is unknown, although it is logical to assume it is from faulty innervation of eye muscles.
Fig. 3: Fixation disparity as a function of the forced vergence angle which is induced by base-in prisms and base-out prisms in front of the eyes. These prism FD-curves have widely been used for subjective fixation disparity and the clinical implications are described below.
Either BASE IN for an exodeviation (eye turned out), BASE OUT for an esodeviation (eye turned in), BASE UP for a hypodeviation (eye turned down) or BASE DOWN for a hyperdeviation (eye turned up). Steps: 1. The patient should be measured in primary position first and then in any other positions of gaze of concern.
Heterophoria is an eye condition in which the directions that the eyes are pointing at rest position, when not performing binocular fusion, are not the same as each other, or, "not straight". This condition can be esophoria, where the eyes tend to cross inward in the absence of fusion; exophoria, in which they diverge; or hyperphoria, in which ...