An isolated column of 20/20 letters is typically the target used to measure the distance lateral phoria and the distance lateral ductions. The above tests were run on 30 subjects and statistically compared with results of the same test procedures performed on the same subjects using an isolated 20/60 letter as the target. Analysis disclosed no statistical differences for either test target for distance lateral phorias or lateral ductions. The isolated 20/60 letter target provides not only sufficient phoria and duction information at the far point but also simplifies and facilitates the examination sequence for subject and examiner alike.
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