US2837964A - Perimeters for the examination of visual fields - Google Patents

Description

June 10, 1958 P. F. M. GAMBS mmmsnsroa was: EXAMINATION OF VISUAL FIELDS Filed March 2, 1954 V llwrrntor PM. rx'eneminum 6N4 as Unite States Patent FOR THE EXAMINATION OF VISUAL FIELDS PERIMETERS Perimeters are instruments used for the examination of the visual field of a patient and for the recording of the results obtained on diagrams. The use of such a record furthers the interpretation of the examination and allows establishing a diagnosis if required.

With most perimeters in use the investigation is performed by projecting a luminous test-spot inside a hemispherical cup forming the perimeter bottom and by shifting it so as to find those positions for which this test spot is perceived by the patient whose eye occupies the center of the hemisphere and who is looking at the pole of said hemisphere.

The practitioner or physician who is proceeding with the investigation stands generally behind the patient and directs by hand a small gun-shaped instrument projecting the luminous spot onto the hemispherical surface. This prior method leads to various drawbacks. such as the following: A

No clear definition of the spot is provided,

The physician cannot readily check in a positive manner the proper centering of the eye which is being examined and he cannot either check the direction given by the patient to his eye.

It is often very difiicult for the physician to define reliably the location of the spot inside the hemispherical surface since the lines or marks drawn to this end are only slightly apparent so as not to exert any disturbing action on the actual examination.

These various drawbacks lead physicians to prefer those perimeters of the hemispheric type which allow them to proceed with the examination while sitting in front of the patient so as to be capable at any moment of checking the position of the patients eye through an opening provided at the pole of the hemisphere. This position of the physician sitting in front of the patient implies that the projection of the spot and the recording of the results are performed in accordance with a method different from that described hereinabove.

In certain instruments, a mechanism which is generally of a complex type makes the spot projecting means move in unison with a stylus which reproduces on a diagram the movements of the spot on the hemisphere. The cost price of such arrangements is generally high.

A further solution of the problem consists in resorting to a hemisphere of plastic material onto the surface of which the spot is projected by a small device located on the outer surface of the hemisphere.

My invention has for its object a perimeter of the last defined type showing the following advantageous features:

The hemisphere is constituted by a sheet of transparent plastic material inside which a layer of dull white paint forms a homogeneous perimeter bottom or screen on which the spot is projected with an unvarying clearness.

The meridian and parallel lines required for finding the location of the spot are engraved on the outer surface of the sphere. Such a hemisphere is preferably associated with a diagram printed on a sheet of translucent preferably made of transparent plastic material.

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material the front surface of which carries general data, and a Writing space while the back carries meridian and parallel lines similar to those drawn on the outer surface of the sphere.

j I have illustrated by way of example in the accompanying drawings a preferred embodiment of my improved perimeter. In said drawings:

Figs. 1 and 2 are views showing respectively in side and front views the hemispherical perimeter as seen from the outside.

Fig. 3 is a partial plan view on a reduced scale of the record sheet of translucent paper as seen by the practitioner during his examination of the patient.

The cup-shaped member 2 forming the perimeter is Its pole 3 is provided with an opening through which the physicianmay see the eye of the patient whose head occupies in the usual manner a predetermined position defined by the fact that it rests on a stand 4 rigid with the body of the instrument and carrying a chin-rest 5 and a forehead-rest 6.

On the outer surface of the cup shaped member 2 are engraved the meridian lines '7 and the parallel lines 8, the figures on which are drawn with a suitable angular setting so that they may be read directlyby the practitioner for which they are perfectly apparent whereas they are not visible for the patient.

These'meridian and parallel lines are essential for defining the location of the spot and their engraving must be executed by means of mechanical means which ensure a correct positioning of said lines even if, by reason of 7 its manufacture, the cup shaped member does not assume a perfectly spherical shape.

A projector 9 produces a beam forming a spot on the inside of the cup-shaped member, said spot appearing through the wall of the latter so as to be visible to the patient on the inside of said member.

The diagram sheets of Fig. 3, to be used for recordin the location of the spots which are of interest are printed as if through a mirror on translucent paper such as tracing paper for instance. In addition to the reproduction of the meridian lines, this diagram includes a chart of values and locations for recorded data, said charts and locations being printed normally in contradistinction to the meridian and parallel lines. Printed legends such as recording and reading for instance are provided so as to define which surface of the tracing paper is to be used selectively according as to whether a record is to be made on the paper or the record is supposed to be read therefrom.

This arrangement of legends printed on the front and back sides allows an easier and speedier recording and cuts out all errors which might arise, as a consequence of an apparent inversion between the left hand and the right hand sections due to the position of the physician sitting in front of the patient. As a matter of fact, said sheets are laid at the moment of the recording on the desk 11 of the instrument facing the physician, but they are turned so that the half of the cup shaped member which corresponds to the left-hand half of the visual field of the patient and which lies to the right of the physician during examination, may be illustrated on each diagram by the right-hand half of the circle forming a representation of the cup-shaped member.

A system of studs and perforations which is not illustrated holds the record sheets on the desk in their correct position. The sheets may be separate or bound together in the manner of the folios of counterfoil book when the sheets have been separated; they show after recording and when seen through the front, the field is assumed to be seen normally by the patient in its usual appearance so that nothing is changed in the conventional and usual interpretation and diagnosis of the record.

In the instrument illustrated, the support 12 for the cup-shaped member is adapted to move laterally over the slide 13 (Fig. 1) of the stand 4, which, is rigid with the arrangement defining the position of the patients head i. e. the chin-rest and the forehead-rest 6. The shifting of the cup-shaped member is controlled by the lateral shifting of the lever 15 in either of the directions illustrated by the arrow 16; this arrangement furthers the centering of the eye to be examined and which is located at 14 whereby the substitution of one eye for the other for examination purposes is performed very speedily. Furthermore, since the head of the patient remains stationary, there is no risk of its tilting as would generally occur if it were submitted to a lateral shifting. Such a tilting alters the results of the examination of the visual field, which examination is always performed with the assumption that the horizontal meridian plane passes through the centers of the right hand and left hand pupils.

Obviously my invention is by no means limited to the sole embodiment which has been more particularly disclosed hereinabove and it covers all the modifications thereof falling within the scope of the accompanying claim, in particular as concerns the means for carrying the cup-shaped members.

What I claim is:

In combination with a perimeter for the examination of the visual field of a patients eye comprising a hemispherical cap of transparent material having a horizontal axis and at the center of which the patients eye to be investigated is to be located, the outer convex surface of the hemispherical cap carrying a series of meridian 'and parallel lines, means shiftable over the outer surface of the cup to form a luminous spot on the inner surface of said cup and a stationary carrier over which the transparent cup is adapted to be shifted transversely with reference to its axis, the provision of a sheet of transparent material adapted to be laid on sm'd stationary carrier to the rear of the transparent cup and carrying on its front surface general data and a writing space on its back in side by side relationship two mirror replicas of the meridian and parallel lines on the convex surface of the transparent cup as projected on a surface perpendicular to the axis of said cup, said replicas being apparent through the transparent sheet to the observer at the rear References Cited in the file of this patent UNITED STATES PATENTS 596,044 Meyrowitz et a1 Dec. 21, 1897 1,780,291 Cameron Nov. 4, 1930 1,970,150 Simmerman Aug. 14, 1934 FOREIGN PATENTS 264,664 Switzerland Feb. 1, 1950 Great Britain Apr. 16, 1952

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