Search results
Results from the WOW.Com Content Network
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]
When measuring horizontal fusion ranges, base in prisms assess fusional divergence while base out prisms assess fusional convergence. The vertical fusional vergence amplitude can also be measured with base up and base down prisms although the horizontal PFR is typically the main focus when testing.
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.
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.
Convergence insufficiency is characterized by one or more of the following diagnostic findings: patient symptoms, high exophoria at near, reduced accommodative convergence/accommodation ratio, receded near point of convergence, and low fusional vergence ranges and/or facility. Some patients with convergence insufficiency have concurrent ...
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.
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.
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.
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.
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. [5] Maddox rod test tutorial. Method for measuring vertical deviations: