Year: 1899

page_text: Date of Application (United Kingdom), in May, 1899
Complete Specification Left, 5th May, 1899-Accepted, 21st Oct., 1899
I, CHALMERS PRENTICE, of Chicago Beach Hotel, 51st Street, Chicago, County:
of Cook, State of Illinois, United States of America, Medical Doctor, do hereby
declare the nature of this invention to be as follows:-
"
The invention designs to provide an improved form of instrument suited for
use by oculists and others in making the shadow test" for the detection of
refractive errors in the eye of a patient. The exact nature of the improvement
will appear in detail from the description following and be more particularly
pointed out by claims at the conclusion thereof.
On the drawings, like parts bear like designation throughout: "
Fig. 1 is a view in horizontal section through the body of the instrument.
Fig. 2, a perspective view of the device mounted upon its supporting stand.
Fig. 3, elevation of the mirror socket-piece, detached. Fig. 4, like view of the
pintle-disc with the mirror secured thereto. Fig. 5, elevation of the mirror
socket-piece, ring frame and adjuncts united. Fig. 6, a central section view of
Fig. 5. Fig. 7, detail of one form of diaphragm. Fig. 8, detail of the seat for
a neutralizing-lens at the patient's eye-piece.
Near the operator's end, the main or focal tube A is united with a lateral
light-supply tube B which opens into it at a slight angle. The two tubes
together constitute the body of the instrument and may be conveniently sus-
tained at desired height by means of the band a which encompasses tube A
and pivots-frictionally-at 6 to the movable leg c, socketed in the usual, sleeve
of base-stand d. Set screw e on the sleeve retains the instrument in adjusted
position while by relaxing screw fat band a it becomes feasible to turn tube A
within said band, thus shifting the tube B from right to left or to some inter-
mediate point in its relation to the main tube.
Internally, each tube A, B is coated "dead black" and at its open end, tube B
has suitable provision for the supply of light rays from some convenient source..
As here shown, the light supply comes from an incandescent electric lamp d',
encased in a holder e which slips on to the terminal of tube B. A reflector f²
at the back of the lamp aids in directing the rays through the tube. A con-
densing lens f¹ interposed in tube B may be used with advantage to project the
pencil of light rays on to the mirror h. An additional condensing lens carried
by supplemental telescoping section of the tube may be used to quickly focus

page_text: the rays at the mirror. Diaphragm 9 set across tube B has a central hole
therein to allow the pencil to pass but being "dead-black" acts to arrest and
absorb the dispersed light which must otherwise affect the desired clearness of
definition. The condensing lens may be discarded and a diaphanous shade be
set across tube B in lieu of diaphragm g but such construction is less effective
in its action.
Mirror is sustained by tube A at a slight incline so that the rays proceed-
ing from tube B are reflected by the mirror and are projected in turn along
tube A toward the eye of the patient. Mirror h may consist of a round bit of
silvered glass; a small central area or peep-hole may be left uncovered as in
the ordinary hand retinoscope. The mirror can be plane but is generally made
concave so as to direct the ray on to the fundus of the eye at the far end of
tube A. If the tube be e.g., 20 inches in length the use of a mirror of like focal
power, say 2 diopters, will relieve the operator from the need of making correc-
tions for this length, in arriving at a final estimate respecting the strength of
the lenses to be prescribed.
The mirror is fastened in some suitable fashion to the flat metal disc i fur-
nished with journal-pintles k, k which seat and turn in holes at ring-frame l.
By making one of the pintles (e.g., k) like a spring bolt, the disc i can be dis-
mounted or be re-set in place at will. Ring-frame nicely fits within the hole
of an annular socket-piece m. Keeper n threaded to frame retains it in place
but still allows for ready rotation of the frame within the hole at socket-piece m.
The frame carries a pointer o to denote the degree of rotation as disclosed by
graduated scale on the face of annulus m. A spring-like nib o¹ cut from the
inner periphery of annulus m bears frictionally against ring-frame to prevent
it prematurely shifting.
The annular socket piece m is snugly fitted at its rim into the operator's end
of focal tube A. By means of handle ? soldered or otherwise secured to disc i
it is seen that the inclination of the mirror can be changed at will on rocking
the disc about its pintles k, k¹. The handle p can also be used to rotate the
ring-frame in its seat thus bringing the pintles into a different plane and
necessarily modifying the effect observed on rocking the mirror at the new.
relation. The device has the same range of adjustment as the hand retinoscope
but becomes more definite because the degree of rotary movement assigned to
ring-frame can be precisely fixed and be repeated, when desired. All internal
parts exposed to the light rays, save only the mirror face, are to be coated "dead
black" to prevent reflection.
:
For convenience, the length of focal tube A is generally constant e.g., 20 inches
although it can be made as shown in telescoping sections to permit of various
adjustment, if desired. The graduated scale at the sections affords proper data
for the calculations of the operator in allowing for differences in length of
the tube.
66
One or more diaphragms q preferably made of conoidal ring-shape may be
set at intervals along the tube. Each diaphragm is coated dead black.' If
more than one be used, the dispersed rays are better excluded and absorbed,
only the central pencil of light being projected through the tube on to the eye
of the patient. A set of diaphragms each having an opening of different size
can be provided, one diaphragm being inserted as a substitute for another, if
deemed desirable.
The eye-piece may consist of a simple ring with central hole, set into the
end of tube A. Or, a fittings may be used at times, adjusted to tube A and
furnished with an open seat for test lens (Fig. 8). By inserting several lenses
of different curvature, the operator is eventually able to prescribe a lens suited
to correct the refractive errors of the eye under examination.
The improved apparatus dispenses with the need of a dark-room. The eye
to be examined rests at the end of the focal tube and is exposed only to the con-
fined rays projected through the tube. The image reflected at the fundus of the

page_text: eye and the shadow which accompanies it become clearly defined and are capable
of nicest observation and study under various manipulation of the operator's
mirror. The free eye can be directed to a distant object which results in further
distention-by sympathy-of the pupil of the eye under treatment. A smaller
pupil can be examined by aid of the confined light without resort to mydriatics.
A plus lens over the free eye induces a certain amount of dilation and by
sympathy induces corresponding dilation in the eye confined to the focal tube.
The plus lens causes the ciliary to relax in the effort to see, and a like relaxa-
tion of the ciliary in the confined eye, reveals a greater amount of latent
hypermetropia than could otherwise be noted.
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:-
1. In retinoscopes, the combination with the focal tube, of the light-supply
tube united at an angle thereto, and the tilting mirror with suitable aperture
therein; said mirror being internally located to receive the light rays and pro-
ject the same along the focal tube to the patient's eye-piece, substantially as
described.
2. In retinoscopes, the combination with the focal tube, of the light-supply
tube united at an angle thereto, and the inclined, rotatable, tilting mirror with
suitable aperture therein; said mirror being internally located to receive the
light rays and project the same along the focal tube to the patient's eye-piece,
substantially as described.
3. In retinoscopes, the combination with the focal tube, of the light-supply
tube united at an angle thereto, the inclined, tilting mirror to receive the light
rays and project the same along the focal tube, and one or more diaphragms inter-
posed in said tube to obstruct and absorb the dispersed rays, substantially as
described.
:
4. In retinoscopes, the combination with the focal tube and with the annular
socket set therein, of the ring-frame rotatably mounted in the socket, and the
mirror disc secured by pintles to obstruct and rock in said frame, substantially as
described.