Importance

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Abstract

A calculating rule for obtaining ophthalmic values which are necessary for making eyeglasses, such as near-point distance, far-point distance, visual range, and addition, especially by which the eyeglasses-wearer can continue his work at the objective working distance with no asthenopia based on accommodation, from other ophthalmic values such as power of the ametropia, accommodation, etc., and for obtaining the resultant prism-diopter and base-direction of the prism for correcting heterophoria. The calculating rule comprises a rectangular slide rule and a circular rotating rule: the slide rule comprising a fixed rule consisting of scale (A) and accommodation and scale (D) of near-point distance, and a slide rule consisting of scale (B) of power of the ametropia equal to addition and scale (C) of far-point distance, and the marks for indicating, on the scale (D), near-point distance and the objective working distances with no asthenopia which vary in accordance with the accommodations; the circular rotating rule comprising a fixed circular rule (E) and a rotating circular rule (F).

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First Claim