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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 in the presence of increasing vergence demands.
Efforts must first be made to identify and treat the underlying cause of the problem. Treatment options include eye exercises, [2] wearing an eye patch on alternative eyes, [2] [24] prism correction, [26] [24] [27] and in more extreme situations, surgery [5] [28] or botulinum toxin. [29]
Horror fusionis is a rare condition and normally appears only in patients who have been treated by means of surgery or other interventions. [2] Attempts to achieve stereoscopic vision, in particular anti-suppression therapy and other orthoptic exercises, may lead to double vision as undesired side effect, in particular also to horror fusionis.
Typical pair of single vision glasses. Single vision lenses correct for only one distance. If they correct for far distance, the person must accommodate to see up close. If the person cannot accommodate, they may need a separate correction for near distances, or else use a multifocal lens (see below).
In the event that correction cannot be worn due to the obstruction of vision through the eye piece, lenses may be placed within the lens holder before each eye. The examiner instructs the patient to hold the Maddox Wing and identify the number that the white (vertical arrow) and red (horizontal arrow) arrows point to on their respective scales.
The unwanted interference effects are suppressed by vapour-depositing a special dielectric coating known as a phase-compensating coating on the roof surfaces of the roof prism. These phase-correction coating or P-coating on the roof surfaces was developed in 1988 by Adolf Weyrauch at Carl Zeiss [6] Other manufacturers followed soon, and since ...
Prism lenses set to make minor optical changes in the vertical alignment may be prescribed instead of or after surgery to fine-tune the correction. Prism lenses do not address torsional misalignment and this may limit their use in certain cases. An additional consideration of prism lenses is that they must be worn at all times.
An Amici prism, named for the astronomer Giovanni Battista Amici, is a type of compound dispersive prism used in spectrometers.The Amici prism consists of two triangular prisms in contact, with the first typically being made from a medium-dispersion crown glass, and the second from a higher-dispersion flint glass.