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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.
relevant position of the prism in front of the eye denoted by: base in “BI” or “-” for fusional divergence; base out “BO” or “+” for fusional convergence; base up “BU” or base down “BD” for vertical fusional vergence. what the patient sees when they ‘break’; i.e. “c diplopia” or “c suppression”
- 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.
If test prisms with increasing amount are placed in front of the observer’s eyes, the fixation disparity changes in the eso direction with base-in prisms and in the exo direction with base-out prisms (Fig. 3). These prisms force the eyes to change the vergence angle while the viewing distance remains unchanged.
Exophoria is a form of heterophoria in which there is a tendency of the eyes to deviate outward. During examination, when the eyes are dissociated, the visual axes will appear to diverge away from one another. The axis deviation in exophoria is usually mild compared with that of exotropia.
The base is the thickest part of the lens and is opposite from the apex. Light will be bent towards the base and the image will be shifted towards the apex. In an eyeglass prescription, the base is typically specified as up, down, in, or out, but left and right are also used sometimes.
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.
Cover test. 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 ...
DVD can be revealed on ocular movement testing when one eye is occluded by the nose on lateral gaze. This eye will then elevate, simulating an inferior oblique over action. However, in a unilateral case, overaction of the superior rectus muscle in the unaffected dominant eye, can also be a causing factor as well as causing a V pattern exophoria.
An optical prism is a transparent optical element with flat, polished surfaces that are designed to refract light. At least one surface must be angled — elements with two parallel surfaces are not prisms. The most familiar type of optical prism is the triangular prism, which has a triangular base and rectangular sides.