Improvements in Means and Appliances for Testing the Sight.
Year: 1893

page_text: Date of Application, 9th Oct., 1893-Accepted, 18th Nov., 1893
COMPLETE SPECIFICATION.
Improvements in Means and Appliances for Testing the Sight.
I, NATHAN LAZARUS, of 28 Sutherland Avenue, London, W., Optician, do
hereby declare the nature of my said invention and in what manner the same is to
be performed, to be particularly described and ascertained in and by the following
statement :-
The object of my invention is to effect improvements in means and appliances
for testing the sight in relation to refraction, convergence, and colors.
And in order that my said invention may be particularly described and ascer-
tained, reference is hereby made to the accompanying drawings, in which similar
letters of reference indicate corresponding parts.
Fig. 1 is an elevation of the complete device for testing the sight.
Fig. 2 is an elevation of the back board, with the discs removed.
Figs. 3, 4 and 5 are elevations of the revolving discs.
The back board a, with the 3 revolving discs b, c and d, attached thereto may be
placed in a vertical, or other convenient position, for use.
e is a pivot, upon
which the 3 discs b c and d are capable of being revolved. The back board a has
a half circle delineated thereon, the half circle being divided at every 5 degrees, as
shown. Above the half circle, a horizontal line, broken to receive the arrow, is
drawn, the radial lines from the semicircle, from 10 to 40 degrees being carried to
the horizontal line. Above the arrow the letters E, D, C, L, are delineated ;
under each letter the distance for normal acuteness of vision is indicated in meters.
In and below the semicircle are a number of letters, the sizes of which are graduated
from large to small, as shown, the distance for normal acuteness of vision in metres
being indicated underneath each letter or group of letters.
The first superposed disc b, shown separately in Fig. 3, has two circular
apertures 9 g, and a number of lines and groups of lines, graduated from thick to
thin, as shown.
The secondly superposed disc c, shown separately in Fig. 4, has also two circular
apertures 9 g, the two segmental spaces, on each side of the apertures, being divided
into 6 parts, and colored as indicated.
The thirdly superposed disc d, shown separately in Fig. 5, has also two circular
apertures gg, through which any part or parts of the indicated marks, figures,
letters, or colors, may be seen, the several discs being turned upon their centres by
hand for that purpose.
By the aid of my improved device refraction, and convergence, may be detected,
as well as color blindness.
It is obvious that the disposition and character of the letters and figures may be
varied, and the colors may be otherwise arranged, without departing from the
nature of my invention.
Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is :-
1. In means and appliances for testing the sight, the combination of a base
board a, fitted with superposed revolving discs b cd, each disc having two
apertures 9 g, through which the various lines, letters, numbers, or colors, upon the
base board and discs may be seen; the base board also having various test letters
and figures or numbers, substantially as herein before described and illustrated by
the drawings.
2. The general construction, arrangement and combination of the several and

page_text: respective parts, together forming my invention of improvements in means and
appliances for testing the sight, substantially as herein before described and illus-
trated by the drawings.
Dated 07th Santambor 1900
GEO.
DOWNING,
8, Quality Court, London, W.C., Agent.