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Prism fusion range. The prism fusion range ( PFR) or fusional vergence amplitude is a clinical eye test performed by orthoptists, optometrists, and ophthalmologists to assess motor fusion, specifically the extent to which a patient can maintain binocular single vision ( BSV) in the presence of increasing vergence demands. Motor fusion is ...
The two primary types of cover tests are: the alternating cover test. the unilateral cover test (or the cover-uncover test). The test involves having the patient focusing on both a distance as well as near object at different times during the examination.
There are two types of prisms, the first type is glass prisms which need to be held in the prentice position and the second type is plastic prisms that need to be positioned in the frontal plane. [1] Try to estimate the angle of deviation before placing the prism over the affected eye, this way time can be saved in busy clinics and especially ...
Indications for use. The Worth Four Light Test is indicated for use when assessing the binocular functions, the ability of eyes to work in coordination, of an individual. It can be used to develop a diagnosis or to support or confirm an initial diagnosis.
Prism correction is measured in prism dioptres. A prescription that specifies prism correction will also specify the "base". 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.
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 .
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.
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.
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 ...
Near-vision subjective fixation disparity (sFD 0) tends to be larger in the exo direction and the aligning prisms (sP 0) tends to be more base-in, suggesting that the eyes tend to under-converge. [34] [35] [36] [37] Most of these studies used the Mallett-unit, which consists of a small central fixation letter X surrounded by two letters O, one ...