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Prism dioptres. Prism correction is commonly specified in prism dioptres, a unit of angular measurement that is loosely related to the dioptre. Prism dioptres are represented by the Greek symbol delta (Δ) in superscript. A prism of power 1 Δ would produce 1 unit of displacement for an object held 100 units from the prism. [2]
Amblyopia. Anisometropia is a condition in which a person's eyes have substantially differing refractive power. [1] Generally, a difference in power of one diopter (1D) is the threshold for diagnosis of the condition. [2][3] Patients may have up to 3D of anisometropia before the condition becomes clinically significant due to headache, eye ...
assess degree of binocular vision. The Worth Four Light Test, also known as the Worth's four dot test or W4LT, is a clinical test mainly used for assessing a patient's degree of binocular vision and binocular single vision. Binocular vision involves an image being projected by each eye simultaneously into an area in space and being fused into a ...
Esotropia (from Greek eso 'inward' and trope 'a turning' [1]) is a form of strabismus in which one or both eyes turn inward. The condition can be constantly present, or occur intermittently, and can give the affected individual a "cross-eyed" appearance. [2] It is the opposite of exotropia and usually involves more severe axis deviation than ...
Esophoria is an eye condition involving inward deviation of the eye, usually due to extra-ocular muscle imbalance. It is a type of heterophoria. Cause
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 largely accounted to ...
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).
The symptoms and signs associated with convergence insufficiency are related to prolonged, visually demanding, near-centered tasks. They may include, but are not limited to, diplopia (double vision), asthenopia (eye strain), transient blurred vision, difficulty sustaining near-visual function, abnormal fatigue, headache, and abnormal postural adaptation, among others.