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A fixation disparity is not constant within a certain observer, but can vary depending on the viewing conditions. 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).
Some cases of convergence insufficiency are successfully managed by prescription of eyeglasses, sometimes with therapeutic prisms. Pencil push-ups therapy is performed at home. The patient brings a pencil slowly to within 2–3 cm (0.79–1.18 in) of the eye just above the nose about fifteen minutes per day five times per week.
[2] Accommodative vergence: blur-driven vergence. Fusional vergence (also: disparity vergence, disparity-driven vergence, or reflex vergence [2]): vergence induced by a stimulus to binocular fusion. Proximal vergence: vergence due to the awareness of a fixation object being near or far in the absence of disparity and of cues for accommodation ...
Although glasses and/or patching therapy, exercises, or prisms may reduce or help control the outward-turning eye in some children, surgery is often required. A common form of exotropia is known as "convergence insufficiency" that responds well to orthoptic vision therapy including exercises. This disorder is characterized by an inability of ...
The strength of the prism is increased until the streak of the light passes through the centre of the prism, as the strength of the prism indicates the amount of deviation present. The Maddox rod is a handheld instrument composed of red parallel plano convex cylinder lens , which refracts light rays so that a point source of light is seen as a ...
Numbers and arrows should be seen clearly. Relaxation of accommodation can result in an increase in exophoria and a decrease in esophoria, leading to an inaccurate result; The examiner should check the function of the Maddox Wing Instrument before use; the septa can be easily bent, leading to the septa not covering the intended view.
There are 2 parts to the Cover Test (CT), which include the cover and uncover component and the alternate cover test. Prior to proceeding, ensure that there is sufficient light in the room so that the examiner can clearly see the patient's eyes. Sit approximately 30 cm away from the patient to ensure you are able to observe their eye movement.
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".