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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]
Specialty. Neurology. Congenital fourth nerve palsy is a condition present at birth characterized by a vertical misalignment of the eyes due to a weakness or paralysis of the superior oblique muscle. Other names for fourth nerve palsy include superior oblique palsy and trochlear nerve palsy. [1] When looking to the right/left the nerve/muscle ...
Aphakia is the absence of the lens of the eye, due to surgical removal, such as in cataract surgery, a perforating wound or ulcer, or congenital anomaly. It causes a loss of ability to maintain focus ( accommodation ), high degree of farsightedness ( hyperopia ), [1] and a deep anterior chamber. Complications include detachment of the vitreous ...
Specialty. Ophthalmology. Exotropia is a form of strabismus where the eyes are deviated outward. It is the opposite of esotropia and usually involves more severe axis deviation than exophoria. People with exotropia often experience crossed diplopia. Intermittent exotropia is a fairly common condition. "Sensory exotropia" occurs in the presence ...
Chronic progressive external ophthalmoplegia ( CPEO) is a type of eye disorder characterized by slowly progressive inability to move the eyes and eyebrows. [1] It is often the only feature of mitochondrial disease, in which case the term CPEO may be given as the diagnosis. In other people suffering from mitochondrial disease, CPEO occurs as ...
Esotropia, where the eye turns inwards, is more common than exotropia, where it turns outwards. [47] [48] Ptosis , or a drooping eyelid, is a common facial manifestation of Turner syndrome; it usually has no appreciable impact on vision, but severe cases may limit visual range and require surgical correction. [49]
Symptoms. 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.
Corrective lens. A pair of contact lenses, positioned with the concave side facing upward. A corrective lens is a transmissive optical device that is worn on the eye to improve visual perception. The most common use is to treat refractive errors: myopia, hypermetropia, astigmatism, and presbyopia.