Petitioner: Haag-Streit AG
`Petitioner: Haag-Streit AG
`
`Ex. 10(cid:20)(cid:20)
`
`EX. 1011
`
`

`

`United States Patent
`Volk
`
`[19]
`
`[11] Patent Number:
`
`4,738,521
`
`[45] Date of Patent:
`
`Apr. 19, 1988
`
`[54] LENS FOR INDIRECT OPHTHALMOSCOPY
`
`[76]
`
`Inventor:
`
`David Volk, 3336 Kersdale Rd.,
`Pepper Pike, Ohio 44124
`
`[21] Appl. No.: 437,279
`
`[22] Filed:
`
`Oct. 28,1982
`
`Int. c1.4 ................................................ A61B 3/10
`[51]
`[52] US. 01. ..................................... 351/205; 350/432
`[58] Field of Search ................. 351/205; 350/432, 435
`
`[56]
`
`References Cited
`U.S. PATENT DOCUMENTS
`
`........................ 350/432
`9/1984 Shirayanagi
`4,469,413
`FOREIGN PATENT DOCUMENTS
`
`127510 10/1980 Japan ................................... 350/432
`
`Primary Examiner—Rodney B. Bovemick
`Attorney, Agent, or Firm—Baldwin, Egan, Hudak &
`Fetzer
`
`[57]
`
`ABSTRACT
`
`A lens for use in indirect ophthalmoscopy having two
`functions; firstly as a condensing lens converging light
`from an ophthalmoscope light source to the pupil of the
`eye and thereby illuminating the fundus of the eye, and
`secondly and simultaneously as an image forming lens
`
`which forms an aerial image of the fundus of the eye,
`which image is viewed monocularly with a monocular
`indirect ophthalmoscope or binocularly and stereoscop-
`ically with a binocular indirect ophthalmoscope. The
`novel features of the lens of this invention are that both
`the front and back surfaces of the lens are positive
`aspheric surfaces of revolution of conoid type on a
`common axis of revolution, the dioptric power at the
`apex of the front surface of the lens being approximately
`twice that of the apex of back surface of the lens, which
`back surface faces the eye being examined, the eccen-
`tricity of the front surface bearing a definite relationship
`to the eccentricity of the back surface, the eccentricities
`of the two surfaces of the lens being a function of the
`sum of the dioptric powers of the two surfaces of the
`lens, the eccentricities and apical dioptric powers of the
`surfaces of the lens being such that the lens converges
`the light from the ophthalmoscope light source to a
`precise image of the source at the entrance pupil of the
`eye, and simultaneously the lens forms with the light
`emerging from the eye a substantially flat aerial image
`of the fundus of the eye in which images the aberrations
`of the image including curvature, astigmatism and dis-
`tortion are optimally corrected.
`
`8 Claims, 6 Drawing Sheets
`
`. POINT "A"
`
`
`LENS OF TH IS
`
`INVENTION
`
`
`
`
`PARALLEL TO
`CHIEF RAYS
`OPTICAL AXIS OF LENS OF
`THIS INVENTION
`
`SUBSTANTIALLY FLAT
`DISTORTION FREE
`ASTIGMATISM FREE
`AERIAL IMAGE OF
`FUNDUS OF EYE
`
`
`
`
`
`IMAGE 0F POINT “A"
`IN AIR
`
`
`
`POINTS IN FUN DUS
`
`SERVING AS LIGHT
`
`SOURCES
`
`
` CHIEF RAY COINCIDENT WITH OPTICAL
`PARALLEL BUNDLE OF
`AXIS 0F LENS OF THIS INVENTION
`LIGHT RAYS EMERGING
`FROM EMMETROPIC EYE
`INCLUDING CHIEF RAY
`
`

`

`US. Patent
`
`Apr. 19,1988
`
`Sheet 1 of6
`
`4,738,521
`
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`

`

`US. Patent
`
`Apr. 19, 1988
`
`Sheet 2 of 6
`
`4,738,521
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`US. Patent
`
`Apr. 19, 1988
`
`Sheet 3 of 6
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`4,738,521
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`

`US. Patent
`
`Apr. 19
`
`9
`
`1988
`
`Sheet 4 of 6
`
`4,738,521
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`

`

`US. Patent
`
`Apr. 19, 1988
`
`Sheet 5 of 6
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`4,738,521
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`

`

`US. Patent
`
`Apr. 19, 1988
`
`Sheet 6 of 6
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`4,738,521
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`

`

`1
`
`4,738,521
`
`LENS FOR INDIRECT OPHTHALMOSCOPY
`
`This invention relates to an improvement in an opti-
`cal lens for indirect ophthalmoscoIW, which has two
`functions: firstly as a condensing lens converging light
`from an ophthalmoscope light source to the entrance
`pupil of the eye and thereby illuminating the fundus of
`the eye, and secondly and simultaneously, utilizing the
`light emerging from the eye, as an image forming lens
`which forms an aerial image of the fundus of the eye,
`which image is viewed monocularly with a monocular
`indirect ophthalmoscope or binocularly and stereoscop-
`ically with a binocular indirect ophthalmoscope. The
`novel features of the lens of this invention are that both
`the front and back surfaces of the lens are positive
`aspheric surfaces of revolution of conoid type on a
`common axis of revolution, the dioptric power at the
`apex of the front surface of the lens being approximately
`twice that at the apex of the back surface of the lens,
`which back surface faces the eye being examined, the
`eccentricity of the front surface bearing a definite rela-
`tionship to the eccentricity of the back surface, the
`eccentricities of the two surfaces of the lens being a
`function of the sum of the dioptric powers of the apices
`of the two surfaces of the lens, the eccentricities and
`apical dioptric powers of the surfaces of the lens being
`such that light from the lens converges the light from
`the ophthalmoscope light source to a precise image of
`the source at the entrance pupil of the eye, and simulta-
`neously the lens forms with the light emerging from the
`eye a substantially flat aerial image of the fundus of the
`eye in which the aberrations of the image including
`curvature, astigmatism and distortion are optimally
`corrected. As is well known, the term eccentricity is a
`mathematical expression in which eccentricity is de-
`fined as the ratio existing between the distance from any
`point on a curve of a conic section to the focus and to
`the directrix.
`
`BACKGROUND OF THE INVENTION
`
`Sudarsky and Volk, in a paper entitled “Aspherical
`Objective Lenses As an Aid in Indirect Ophthalmos-
`copy, A Preliminary Report,” reported on their investi-
`gation of existing conoid lenses designed for subnormal
`vision when used as condensing lenses for indireCt oph-
`thalmoscopy. As a result of their investigation they
`recommended the use of three powers of conoid lenses
`for use in indirect ophthalmoscopy, the 15, 20, and 30
`diopter lenses, each of the lenses having one aspheric
`surface, the other surface being plano or spherical. In
`use, the front aspherical surface faces the examiner.
`In about 1969, Nikon of Japan introduced aspheric
`lenses for indirect ophthalmoscopy, with the front sur-
`face aSpherical and the back surface spherical.
`Other Japanese manufacturers, including Kowa and
`Topcon, introduced their aspheric lenses for indirect
`ophthalmoscopy late in the 1970 decade. These lenses
`likewise had an aspherical front surface and a spherical
`back surface. In the United States of America, Ameri-
`can Optical Company and Younger Lens Company also
`manufactured and sold indirect ophthalmoscopy lenses
`with one surface aspherical and the opposite surface
`spherical.
`Recently Zeiss of Germany introduced their indirect
`ophthalmoscopy lens with one surface aspherical and
`the opposite surface spherical.
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`45
`
`5O
`
`55
`
`65
`
`2
`In all of the above prior art indirect ophthalmoscopy
`lenses, only one of the two surfaces is aspheric. Al-
`though such aspherical indirect ophthalmoscopy lenses
`are a great improvement over spherical indirect oph-
`thalmoscopy lenses, lens aberrations still remain so that
`as a condensing lens the light from the ophthalmoscope
`light source is not converged to a sharply defined image
`at the entrance pupil of the eye, and as an image forming
`lens, the aerial image of the fundus is curved away from
`the examiner and is increasingly astigmatic perpheral-
`ward.
`
`BRIEF DESCRIPTION OF THE PRESENT
`INVENTION
`
`In the novel indirect ophthalmoscopy lens of this
`invention, both surfaces are positive conicoids of revo-
`lution on a common axis. The dioptric power at the
`apex of the back surface is approximately one-half that
`of the dioptric power at the apex of the front surface.
`The nominal dioptric power of any indirect ophthal-
`moscopy lens of this invention is the sum of the apical
`dioptric powers of the front and back surfaces of the
`lens; for example the dioptric power at the apex of the
`front surface may be 10 diopters and at the apex of the
`back surface 5 diopters or 9 and 4.5 diapters respec-
`tively, and the nominal power is 15 diopters. A lens of
`this invention may have a nominal dioptric power
`within the range of from 15 diopters to 50 diopters.
`The diameter of an indirect ophthalmoscopy lens is
`generally some value between 52 mm and 31 mm, the
`lower power lenses having the larger diameters. In
`Table I, column I,
`TABLE I
`
`
`Diopter
`Large Lenses (MM)
`Small Lenses (MM)
`10
`52
`38
`20
`49
`37
`25
`46
`36
`30
`43
`35
`35
`4O
`34
`40
`37
`33
`45
`34
`32
`50
`31
`31
`31
`
`55 31
`
`I have listed several lens powers within the range of 10
`to 55 diopters, and in column 2 suggested lens diameters
`in millimeters which may be considered larger diameter
`indirect ophthalmoscopy lenses, and in column 3 of said
`table I have listed for the same lens powers suggested
`diameters in millimeters which may be considered small
`indirect ophthalmoscopy lenses. Generally a lens of 31
`mm is quite satisfactory for the 50 and 55 diopter lens,
`and I have therefore suggested only a single diameter
`for these lenses, although a dimeter other than 31 mm
`may be utilized.
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIG. 1 is a graph of nominal dioptric power versus
`suggested diameters in millimeters of lenses incorporat-
`ing the present invention;
`FIG. 2 is a schematic illustration of the eye and a lens
`of the present invention combined to form a telecentric
`system;
`FIG. 3 is a schematic sketch illustrating the formation
`of an aerial image of the fundus with the eye and the
`lens of this invention combined as a telecentric system;
`FIG. 4 is a schematic illustration of an ophthalmo-
`scope illuminating system showing the diverging rays
`
`

`

`3
`from the ophthalmoscope mirror and their coincidence
`upon a lens of this invention and the refraction of these
`rays to converge them to an image of the source at the
`center of the entrance pupil of the eye to illuminate the
`interior posterior part of the eye;
`FIG. 5 is a schematic illustration of the formation of
`an aerial image of the fundus of the eye by the lens of
`this invention; and
`FIG. 6 is a schematic illustration of an ophthalmo-
`scope observing system for observation of the aerial
`image produced by the lens of this invention showing
`how said image can be viewed binocularly and stereo-
`scopically.
`
`DETAILED DESCRIPTION OF INVENTION
`
`Referring now to FIG. 1, a graph is illustrated of
`nominal dioptric power versus diameter in millimeters
`of indirect ophthalmoscopy lenses. The upper curve in
`the graph represents at any given point a suggested
`diameter for the lens power represented by that point,
`for lenses which may be termed large lenses. The lower
`curve in FIG. 1 is that for lenses which may be termed
`small indirect ophthalmoscopy lenses. FIG. 1 is only
`suggestive and lenses of diameters intermediate be-
`tween the two curves, or larger or smaller than those
`represented by the upper and lower curves respectively
`can be utilized. The dotted line portions of FIG. 1 rep-
`resent useful lenses with powers and associated diame-
`ters which are also considered as being within the scope
`.of this invention, while the continuous line portions
`represent those lenses with preferred power and associ-
`ated diameters. Lens powers between 10 and 15 diop-
`ters may be utilized when extreme magnification in the
`aerial image is desired while lens powers between 50
`and 55 diopters may be utilized to increase the amount
`of fundus included in the aerial image.
`A first feature of the design philosophy which I have
`utilized as a basis in the design of the novel lens of this
`invention is that the lens and the eye form a telecentric
`system as shown in FIG. 2 wherein the secondary focus
`of the lens is at the center of the entrance pupil of the
`eye. Thus a homocentric bundle of coaxial and parallel
`light rays incident upon the front surface of the lens will
`be converged or condensed to a single point at the
`secondary focus of the lens which falls at the center of
`the entrance pupil of the eye. FIG. 2 is illustrative of the
`telecentric lens~eye combination just described, with
`the light rays proceeding beyond the pupil to illuminate
`the posterior portion of the interior of the eye. Simulta-
`neously each illuminated point at the back of the inte-
`rior of the eye sends out light in all directions, with
`homocentric bundles of light rays passing through the
`pupil of the eye. Assuming that the eye is a perfectly
`emmetropic eye, each bundle of light rays emerging
`from the eye will be a parallel bundle of light rays with
`the chief ray of each bundle passing through the center
`of the entrance pupil of the eye to be incident upon the
`indirect ophthalmoscopy lens as shown in FIG. 3 and
`then refracted by the lens to proceed parallel to the axis
`of the lens. A second feature of the design philosophy of
`the lens of this invention is that the indirect ophthalmos-
`copy lens is so designed that while in its telecentric
`position with respect to the eye as shown in FIG. 3, it
`refracts the emerging homocentric parallel bundles of
`light rays surrounding each chief ray such that it forms
`a substantially flat, astigmatism free undistorted aerial
`image of the fundus of the eye in the anterior focal plane
`of the lens. FIG. 3 illustrates the second design feature.
`
`4,738,521
`
`4
`In order to utilize such a telecentric system as illustrated
`in FIGS. 2 and 3, both the light source and the observ-
`ing system of the ophthalmoscope would have to be at
`an infinite distince from the observed eye. As used in
`practice, both the light source and the observing system
`of the ophthalmoscope are relatively close to the ob-
`served eye with the light rays diverging from a virtual
`source toward the indirect ophthalmoscopy lens. The
`image of the virtual light source as formed by the indi-
`rect ophthalmoscopy lens is consequently slightly far-
`ther from the lens than the secondary focus of the lens.
`Consequently the lens must be moved forward a small
`amount in order that the image of the source be formed
`at the center of the entrance pupil of the eye. FIG. 4
`illustrates light rays originating from a small filament F
`within the ophthalmoscope and after refraction by lens
`C, being reflected as a diverging bundle of light rays
`from mirror M toward the indirect ophthalmoscopy
`lens I of this invention.
`FIG. 5 illustrates image formation by the indirect
`ophthalmoscopy lens, the image of the fundus being
`substantially flat, undistorted and free of astigmatism
`and formed in the anterior focal plane of the indirect
`ophthalmoscopy lens, with the chief rays of bundles of
`light rays emerging from the lens being convergent.
`FIG. 6 illustrates the optical principals of the observing
`system of
`the binocular
`indirect ophthalmoscope
`wherein each bundle of light rays proceeding from the
`aerial image of the fundus toward the ophthalmoscope
`is divided by a central mirror system to proceed toward
`right and left prisms which in turn direct the light rays
`toward the observer’s eyes. The departure of indirect
`opthalmoscopy lens from the idealized telecentric mode
`wherein the chief rays from the aerial image proceed
`toward infinity has been taken into account in the de-
`sign of the novel lens of this invention.
`lens
`In my research on the lens of this invention,
`design parameters have been determined for a large
`number of lenses designed with both surfaces convex
`conoids with a wide range of apical dioptric powers for
`each of the two surfaces and a wide range of eccentrici-
`ties for each of the two surfaces of the lens. The optical
`material considered in this research consisted primarily
`of ophthalmic drown glass of index of refraction 1.523
`and secondarily of ophthalmic plastic of index of refrac-
`tion 1.498. Glass is preferred because of its resistance to
`scratching and because it can be multicoated to increase
`light transmission to better than 99% and thereby re-
`duce len surface reflection. My research also includes
`lenses made of transparent glass of various colors in-
`cluding white or clear which transmits the entire visible
`spectrum; yellow which transmits light in the green-yel-
`low-orange-red portion of the visible spectrum; orange-
`red which transmits light in the orange-red portion of
`the visible spectrum; green which transmits light in the
`green portion of the visible spectrum; and blue which
`transmits light in the violet-blue and green-yellow por-
`tions of the visible spectrum.
`_
`I have determined in my research that the design of
`the lens of this invention has the following identified
`relationships between its various parameters.
`The lens material is a homogenous transparent optical
`material formed of either glass or plastic and having
`two positive or convex aspheric surfaces of revolution
`on opposite sides thereof, each having its own axis and
`wherein the two axes coincide, and which lens is in-
`tended to be supported before a patient’s eye at a dis-
`tance that is substantially equal to the secondary focal
`
`5
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`

`

`4,738,521
`
`5
`
`10
`
`15
`
`20
`
`25
`
`30
`
`6
`revolution of conoid type on opposite sides thereof and
`means for holding said lens to enable the same to be
`supported in the hand of the examiner before a pateint’s
`eye at a distance substantially equal to the secondary
`focal distance of the lens with the optical axis of the lens
`passing through the center of the entrance pupil of the
`patient’s eye, one of the aspheric surfaces of revolution
`being defined as the front surface which faces the exam-
`iner and the other aspheric surface of revolution being
`defined as the back surface which faces the eye being
`examined, and wherein the nominal dioptric power of
`the lens is defined as the sum of the dioptric powers of
`each of the two surfaces at its apex and which nominal
`dioptric power is within the range of approximately
`10—55 diopters, and wherein the dioptric power at the
`apex of the front surface is within the range of approxi-
`mately 6.666 to 36.666 diopters and wherein the dioptric
`power at the apex of the back surface is selected to be
`within the range of approximately 3.333 to 18.333 diop—
`ters, and wherein for any lens the selected dioptric
`power of the front surface at its apex is approximately
`twice the dioptric power of the back surface at its apex,
`and wherein the eccentricity of the front surface is in
`the range of 0.80 to 1.45 and the eccentricity of the back
`surface is in the range of 0.50 3.80, and wherein for a
`given selected eccentricity for the front suface within
`said range the eccentricity of the back surface is so
`selected as to provide an aerial image of the fundus of
`the examined eye which least departs from a substan-
`tially flat astigmatism free image of said fundus and
`which enables clear observation of the full extent of the
`extent of the aerial image of the fundus of the eye by the
`examiner.
`2. A lens as in claim 1 in which the homogeneous
`transparent optical material is glass.
`3. A lens as in claim 1 in which the homogeneous
`transparent optical material is plastic.
`4. A lens as in claim 1 of orange-red color in which
`the spectral transmission of the homogeneous transpar-
`ent optical material is high and limited almost entirely
`to the orange-red portion of the visible spectrum.
`5. A lens as in claim 1 of green color in which the
`spectral transmission of the homogeneous transparent
`optical material is high and limited almost entirely to
`the green portion of the visible spectrum.
`6. A lens as in claim 1 of yellow color in which the
`spectral transmission of the homogeneous optical mate-
`rial is high and limited almost entirely to the green-yel=
`low-orange-red portion of the visible spectrum.
`7. A lens as in claim 1 of blue color in which the
`spectral transmission of the homogeneous transparent
`optical material is high and limited almost entirely to
`the violet-blue and green-yellow portions of the visible
`spectrum.
`8. A lens as in claim 1 in which the homogeneous
`transparent optical material is fully transparent for the
`entire visible spectrum.
`at
`*
`It
`i
`It
`
`5
`distance of the lens and with the optical axis of the lens
`passing through the center of the entrance pupil of the
`patient’s eye. One of the aspheric surfaces of revolution
`is defined as the front surface of the lens and it faces the
`examiner, and the other aspheric surface of revolution is
`defined as the back surface of the lens and faces the eye
`being examined.
`The nominal dioptric power of the lens is defined as
`the sum of the dioptric power of each of the two lens
`surfaces at its apex and which nominal dioptric power
`may vary within the range of approximately 15 to 50
`diopters. The dioptric power at the apex of the front
`surface may vary within the range of approximately 10
`to 33.333 diopters and the dioptric power of the back
`surface may vary within the range of 5 to 16.666 diop
`ters.
`
`As previously indicated, this is the preferred range
`whereas useful nominal dioptric powers may encom-
`pass a range of approximately 10 to 55 diopters. Fur-
`ther, for any lens of this invention the selected dioptric
`power of the front surface at its apex is approximately
`twice the dioptric power of the back surface at its apex.
`The eccentricity of the front surface may be selected
`to be any value within the range of 0.80 to 1.45.
`The eccentricity of the back surface may lie within
`the range of 0.50 to 3.80, and for a given selected eccen-
`tricity for the front surface within said range the eccen-
`tricity of the back surface is so selected as to provide an
`aerial image of the fundus of the examined eye which
`least departs from a substantiallY flat astigmatism free
`image of negligible distortion of the fundus of the eye
`and which enables clear observation of the full extent of
`the aerial image of the fundus of the eye by the exam-
`iner.
`
`In using the lens of the present invention, it is used in 35
`conjunction with a suitable eye illuminating and observ-
`ing system such as the system illustrated schematically
`in FIGS. 4 and 6.
`In the system, the lens of this invention is held by the
`examiner in spaced relation in front of the examined eye
`at a distance substantially equal to the secondary focal
`distance of the lens, and with the optical axis of the lens
`lying in the plane which contains the entrance pupil of
`the observed eye as well as those of the observer, and
`with the optical axis of the lens lying in said plane and 45
`passing through the center of the entrance pupil of the
`observed eye and passing midway between the entrance
`pupils of the observer’s eyes.
`In this system, the lens of the present invention thus
`produces an aerial image of the fundus of the examined 50
`eye that is substantially flat, and substantially free of
`astigmatism and distortion, thus enabling clear observa-
`tion by the examiner of the aerial image of the fundus of
`the examined eye.
`I claim:
`
`55
`
`1. An indirect ophthalmoscopy lens for use in examin-
`ing a patient’s eye comprising a homogeneous transpar—
`ent optical material having two aspheric surfaces of
`
`60
`
`65
`
`