US2155171A - Instrument for the examination of eyes - Google Patents

Description

April 18, 1939. H. RN'NE 2,155,171

INSTRUMENT FOR THE EXAMINATION OF EYES Filed May 2l, 1956 2 Sheets-Sheet l nvenfar:

Wma/'Cm April 18, 1939. Hl RNNE 2,155,171

INSTRUMENT FOR THE XAMINATION OF EYES Filed May 2l, 1956 2 Sheets-Sheet 2 In venor:

Patented Apr. 18, 1939 UNITED'STATES PATENT ori-ICE 2,155,171 INSTRUMENT FORE'IIlIgl EXAMINATION 0F Henning Rnne, Copenhagen,

Denmark, assignor to the firm C arl Zeiss, Jena, Germany Application May 21, 1936, Serial No. 81,031 In Germany May 25, 1935 1 Claim.

images an illuminated slit on the eye part to' K .be examined, and the luminous intensity of a portion of the pencil of light is weakened by optical means until the luminous intensity of the Tyndall effect produced by this weakened vlight ,l in the cornea corresponds to that of the Tyndall eiect produced by the unweakened portion of the said pencil in the aqueous humour yof the anterior chamber of the eye. As the proportion of albumen in the cornea can be assumed to be constant enough in such an examination of the eye, the luminous intensity of the Tyndall effect can be considered as sufliciently constant also within the cornea, and as this-intensity is substantially greater than the luminous intensity of the Tyndall eiect in the aqueous humourof the anterior chamber, the magnitude of the weakening of the light provides a measure for the determination of the proportion of albumen in the aqueous humour. Experiments have proved that a change in the proportion of albumen can increase the luminous intensity of the Tyndall eiect in the aqueous humour of the anterior chamber to a thousand times its lowest magnitude. It is therefore appropriate to equip the slit lamp for the examination with a lightabsorbing plate of changeable effective thickness, and to provide that this plate can reduce to a -thousandth the luminous intensity of part of the pencil of light emanating from the lamp, the said light-absorbing plate conveniently consisting of two wedges of grey glass which can be moved relatively to each other. Instead of one light absorbing plate of changeable effective thickness, use can be made of a plurality of plates which have different light absorbingcapacities and are attached to the slit lamp by means of a changing device. These light-absorbing plates are graded conveniently from 0 to 3 photopters. Photopters' are units which vhave been used by Professor Tscherning for determining the absorption capacity of grey glasses, glass of one photopter absorbing 90%, or being traversed by one tenth, of the light, glass of two and three photopters being traversed by one hundredth and one thousandth of the light, re-

spectively. It is especially convenient toy yuse light-absorbing plates graded according to quarters of a photopter, since the unavoidable measuring errors are below a damping magnitude of one quarter photopter. The device for changing these plates of different light absorbing capacities may be a slide which contains different plates of grey glass next to each other and is introduced into a guide in the housing of the slit lamp, or it may be a rotatable disc in which thegrey-glass plates are radially disposed.

The instrument according to the invention is illustrated by way of example in the accompanyl ing drawings.

Figure 1 represents this cally, partly in section.

Figure 2 is a view of the changing device vided with light-absorbing glass plates.

instrument schemati- Figure 3 represents on a larger scale the path of the light rays emitted by the source of light and shown in Figure l.

Figures 4 and 5 show the microscopically viewed luminous eld of the light pencil'in the cornea and in the aqueous humour of the anterior chamber of the eye, the lower part of the pencil oi light which enters the eye being less weakened by a grey glass placed in this part of the pencil of light than the corresponding part of the pencii of light in Figure 5.

For the determination of the proportion of albumen in the aqueous humour of the anterior chamber of an eye, there is used according to Figure 1 a Gullstrand slit lamp whose source of light I is imaged by means of atwo-lens condenser 2 at the locus of a convergent lens 4 held by a bracket 3. By means of the lens t of the slit lamp, a slit 5 in the path of the rays is imaged on that part of the eye 6 which is to be examined, this part being viewed by means of a binocular microscope 8 In front of the slit 5, the

having two objectives l. front wall 9 of the lamp housing IIJ is provided with a changing device constituted by a disc II whichis rotatable about a pin I2 and has thirteen I3. Each of the slits I3, a. slit radially disposed slits I3 being excepted,

is partially covered by a plate I4 of grey glass, so that only a denite part of the pencil of rays traversing each of these slits I 3 can proceed unweakened from the slit lamp. The transparencies of the plates I4 are dampngmagnitudes of the graded according to quarters of a photopter from 1A to 3 photopters. 'IZhe plates I 4 are indicated in photopters on round glass plates I5 between the slits I3. In the front wall I 0, and near the slit 5, is

9 of the lamp housing provided a window I 6 in which there appears the number plate Il corresponding tothe plate I4 in front of the slit l and illuminated by the source of light I. Accordingly, an observer can read direct, at any time. the photopter magnitude corresponding to the plate I4 in iront of the slit l.

When the instrument is to be used, the source of light is switched on, and the eye l to be examined is given such a position that the pencil of light enters the anterior chamber I'l oi the eye `and the real image of the slit is projected approximately on the front vsurface Il of the eye lens. The section of the eye I, which is illustrated in Figure 1, as well as a planecontaining the axes of the two microscope objectives 1 lie in reality in a plane at right angles to that of the drawings, which contains the principal axisgovf the slit lamp. By means of a plate Il of grey glass in front of the slit 5, the part of the pencil of rays traversingthis plate is damped and therefore easily distinguishable by its reduced luminous intensity from the other part ot the ray pencil traversing the slit I3 (ci. Figure 3). Each of the parts a and b of the light. beam produces a Tyndall eilect in the cornea I9 as well as in the aqueous humour in the anterior chamber I1. 'I'he proportion oi albumen' is now ascertained by turning the disc I I by hand until such a plate of grey glass is in front of the slit 5 as damps the luminous intensity of the Tyndall effect in the cornea I9 so much that this intensity is the same as the luminous intensity of the Tyndall eiiect of the undamped pencil of light in the aqueous humour in the anterior chamber II. Figures 4 and 5 illustrate in the cornea and in the aqueous humour of the eye S the microscopic view of the luminous eld of the pencil of light passing through the slit I3. For the sake oi a clear representation of the pencil of light, the slit is assumed to be ,quadrilateraL In Figure 4, the pencil oflight in the albuminous humour I'l is still darker than that in the cornea I9, so that the grey glass placed into the ray vpath is not yet dark enough. in Figure 5, in which the pencils of light in the aqueous humour I'I and in the cornea I9 are equally bright. Subsequently thereto, the damping magnitude is read in the window I6, this magnitudebeing a measure for the proportion of albumen in the aqueous humour of the anterior chamber of the eye under examination.

I claim:

An instrument for measuring the albumen in the aquous humour ot the anterior chamber'of an eye to be examined, comprising a light source, a slit diaphragm receiving the rays emanating from said light source. an optical system imaging said'slit on the iront surface of the lens of the eye under examination, a disc having radially disposed openings rotatably mounted cn a pin lying outside the ray path, said disc being close to The correct grey glass isused said slit diaphragm and adapted to be rotated so as to align the respective openings with the slit diaphragm, the axis of said pin being parallel to the axis of said optical system, the axis of rotation of said disc being substantially equidistant from the center o1' said openings and the axis of said optical system, a plurality of light absorbing plates of different densities, one plate being mounted in each of said openings, each of said plates being of smaller area than the respective openings in the disc thereby providing an unobstructed path for aportion of the rays, and

means for indicating the light-absorbing capacity of said plates.

HENNING RNNE.

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