State of Refraction of all Eyes with Exactness. TO TEST ACUTENESS OF
Year: 1885

page_text: State of Refraction of all Eyes with Exactness.
I NATHAN LAZARUS of N° 1 Mangoe Lane in Calcutta at present residing at
No 24 Lanhill Road London W. Oculist Optician, do hereby declare the nature of
my Invention for AN IMPROVED REFRACTION TEST TO TEST ACUTENESS OF VISION
AND STATE OF REFRACTION OF ALL EYES WITH EXACTNESS, to be as follows:-
The object of my invention is to test the acuteness of vision and state of refrac-
tion of all eyes with exactness and that with far greater ease quickness and
simplicity than any other test at present known.
My invention consists of :-
1st A circular disc revolving on a pivot painted or printed white around the
margin of which are groups of lines painted or printed black of different thicknesses
representing the different distances each is distinguishable at by normal vision.
2nd A second circular disc painted black revolving on the same pivot and placed
in front of the first and having a segment in the shape of a wedge cut from the
margin just large enough to expose to view any one group of lines on the inner
dial.
3rd A back plate, painted or printed white (with a loop by which it can be
suspended against the wall) on which is delineated in black a semi circle having
radiating lines at equal distances marked to the different numbers of degrees from
the central vertical line.
4th A pivot passes through the back plate, and on this both circular discs
(separated by washers of sufficient thickness) revolve and are so placed as to allow
the margin of the discs to come exactly under the radiating lines.
5th A screw nut on the outer end of the pivot fastens the whole together.
Hitherto square letters which have lines and subdivisions equal in breadth to
one fifth of the height of the letters, placed at such a distance that their height is
seen under a usual angle of five minutes and which letters are distinctly legible to
the normal eye have been in general use and answer admirably except in cases of
persons who are illiterate those who have no knowledge of Roman characters and
cases of astigmatism where the refraction is unequal in the different meridians of
the eye.

page_text: These tests being composed of groups of lines are universally understood If
lines running in diffirent directions are clearly distinguishable it necessarily
follows that letters would be and vice versa the turning of the dial exposing
groups of lines alternately in the different meridians makes the presence and
diagnosis of astigmatism known at once, avoiding the confusion which always
exists when using the tests hitherto known.
t
State of Refraction of all Eyes with Exactness.
! I NATHAN LAZARUS, late temporarily of 8 Quality Court London W.C. but now
of No 1 Mangoe Lane, Calcutta in British India, Oculist Optician do hereby declare
the nature of this invention and in what manner the same is to be performed, to
be particularly described and ascertained in and by the following statement :-
My invention has for its object to test the acuteness of vision and state of
refraction of all eyes with exactness and that with far greater ease quickness and
simplicity than any other test at present known:-The following is a description
of my invention-It consists of 1st a circular disc A revolving on a pivot, painted
or printed white around the margin of which are groups of lines painted or printed
,black of different thicknesses representing the different distances such is dis-
tinguishable at by normal vision 2-a second circular disc B revolving on the
same pivot and placed in front of the first and having a segment in the shape of a
wedge or square cut from the margin, just large enough to expose to view any one
group of lines on the inner dial-3-a back plate C painted or printed white (with
a loop D by which it can be suspended against the wall) on which is delineated in
black a semicircle having radiating lines at equal distances marked to the different
numbers of degrees from the central vertical line 4-a pivot E passes through the
back plate and on this both circular discs (separated by washers of sufficient thick-
ness) revolve and are so placed as to allow the margin of the discs to come exactly
under the radiating lines-5-a screw nut on the outer end of the pivot fastens
the whole together.
Hitherto square letters which have lines and subdivisions equal in breadth to
one fifth of the height of the letters, placed at such a distance that their height is
seen under a visual angle of five minutes, and which letters are distinctly legible
to the normal eye have been in general use and answer admirably except in cases

page_text: of persons who are illiterate, those who have no knowledge of Roman Characters,
and cases of astigmatism where the refraction is unequal in the different meridians
of the eye-my tests being composed of groups of lines are universally understood
If lines running in different directions are clearly distinguishable it necessarily
follows that letters would be and vice versa, the turning of the dial exposing
groups of lines alternately in the different meridians makes the presence and
diagnosis of astigmatism known at once avoiding the confusion which always exists
when using the tests bitherto known.
Having now particularly described and ascertained the nature of my said
Invention and in what manner the same is to be performed I declare that what
I claim is-
1st The arrangement of the discs forming the refraction test in the manner
substantially described above and as shown in the accompanying drawings.
2d The forming of the refraction test by lines instead of figures as being more
readily and universally understood.
3d The simplification by this means of the discovery and diagnosis of astig-
matism and the avoidance of the confusion at present experienced.
N. LAZARUS.