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THE TWIN CYLINDER: A REFRACTING AID
Author(s) -
PETTINGER DOOGLAS F.
Publication year - 1984
Publication title -
australian journal of opthalmology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.3
H-Index - 74
eISSN - 1442-9071
pISSN - 0310-1177
DOI - 10.1111/j.1442-9071.1984.tb01168.x
Subject(s) - astigmatism , cylinder , refraction , optics , physics , mathematics , geometry
A simple refracting aid is described which differs from the Jackson Cross‐Cylinder in utilizing plain cylinders in a convenient, quickly manipulated form to assist in determining whether astigmatism is present and, in known astigmatism, in deciding whether the power should be increased or decreased by a cylinder alone or with a compensating sphere. It can be used in conjunction with the cross‐cylinder to obtain the final adjustment or it can be used independently, its design with the lenses arranged on opposite sides of a stalk permits rapid change in variations presented to the patient and reduces to‐and‐fro movements of lenses from trial case to trial frame. Key words: refraction, astigmatism, cylinder determination.