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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]
Surgical correction; Surgical correction of the hypertropia is desired to achieve binocularity, manage diplopia and/or correct the cosmetic defect. Steps to achieve the same depend on mechanism of the hypertropia and identification of the offending muscles causing the misalignment.
Visual acuity with eye chart at Near 15.7 inches (400 mm) and without (sc: Latin sine correctore) correctors (spectacles); Ncc is with (cc: Latin cum correctore) correctors. See Visual_acuity#Legal_definitions: VA OS Left visual acuity VA OD Right visual acuity VDU Visual display unit VF Visual field VPS Variable prism stereoscope WD
Treating a case of unsatisfactory alignment often involves prisms, botulinum toxin injections, or more surgery. The likelihood that the eyes will stay misaligned over the longer term is higher if the patient is able to achieve some degree of binocular fusion after surgery than if not.
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.
Hirschberg corneal reflex test. Purpose. whether a person has strabismus. In the fields of optometry and ophthalmology, the Hirschberg test, also Hirschberg corneal reflex test, is a screening test that can be used to assess whether a person has strabismus (ocular misalignment).
If the line appears below the light, there will be a hyper-deviation in which base down prisms are used to measure and correct the deviation. If the line appears above the light, there will be a hypo-deviation and base up prisms are used measure and correct the deviation.
Efforts must first be made to identify and treat the underlying cause of the problem. Treatment options include eye exercises, wearing an eye patch on alternative eyes, prism correction, and in more extreme situations, surgery or botulinum toxin.
Risk factors include premature birth, cerebral palsy, and a family history of the condition. [3] Types include esotropia, where the eyes are crossed ("cross eyed"); exotropia, where the eyes diverge ("lazy eyed" or "wall eyed"); and hypertropia or hypotropia where they are vertically misaligned. [3]
To perform the test you will need. Bagolini Striated Glasses. Pen torch or a distant light source. Alternatively, trial frames and lenses or a lorgnette can be used. In some cases, the use of prisms is necessary to measure a deviation and test for the presence of binocular functions.