title: Estimating the power of a minus spectacle while worn by the patient.
abstract: This paper presents a new method of estimating the power of a minus spectacle lens without removing the spectacle from the patient's face. The examiner shines a small light toward the spectacle and measures the separation between the images reflected from the front and rear surfaces of the lens. The study presents a relationship between separation of reflected images and the power of minus lenses from 0 to -12 D. The article also contains a theoretical explanation of the phenomenon.
mesh_terms: D005139:Eyeglasses / Q000592:standards*; D006801:Humans; D055095:Optics and Photonics; D012029:Refraction, Ocular