Retinoscopy (or shadow test) in the determination of refractions at one meter distance, with the plane mirror / by James Thorington.

  • Thorington, James, 1858-1944.
Date:
1906
Catalogue details

Licence: In copyright

Credit: Retinoscopy (or shadow test) in the determination of refractions at one meter distance, with the plane mirror / by James Thorington. Source: Wellcome Collection.

    33/92 (page 13)
    as the result of the sight-hole in the mirror—two very seri- ous objections. The Luminous Retinoscope (Figs. 7 and 8).—DeZeng Patent.—The latest improvement in retinoscopes is the luminous instrument here described. This instrument is the author’s plane mirror with the electric light attach- ment. A 5-volt electric light with tiny filament is con- tained in a tube placed at an angle of 45 degrees with the handle, and the mirror is correspondingly tilted to an angle of 22 degrees. The light from the filament passes divergently to a strong convex lens which renders the rays less divergent as they fall upon the mirror, and from the mirror the rays pass divergently to the patient’s eye. (Fig. 8.) This instrument has innumerable points of merit: It does away with any use of gas or lamp or cover chimney; the observer is not annoyed with the heat from the gas or lamp; the observer does not have to move the fight or bracket when changing from one distance to another as when working with the gas-light close to the mirror; the electric wires (cords) carrying the current to the filament are of sufficient length to give the observer two meters of space in which to practice the method; the brilliancy of the illumination can be made most intense or diminished very materially with a convenient rheostat; the size of the divergent pencil may be controlled by adjust- ing the condensing lens at the end of the tube. The writer is in the habit of using the mirror with the gas flame until he has obtained an approximate point of reversal and then substitutes the luminous instrument to obtain the more delicate findings; he does this for the reason that if the electric fight is used for any great length of time to find the point of reversal a temporary scotoma is produced that some nervous patients occasionally object to. This luminous instrument will also bring to the notice of the