AU615168B2

AU615168B2 - Magnifying binocular ophthalmoscope

Info

Publication number: AU615168B2
Application number: AU82577/87A
Authority: AU
Inventors: Maximiliaan Joseph Hubertus Cuypers
Original assignee: Lions Eye Institute of Western Australia Inc
Current assignee: Lions Eye Institute of Western Australia Inc
Priority date: 1986-12-10
Filing date: 1987-12-10
Publication date: 1991-09-26
Anticipated expiration: 2007-12-10
Also published as: AU8257787A

Description

-1 COMPLETE AFTER PROVISIONAL

AU)IK(ALIA

PATENTS ACT 1951 SPECIFICATION NO. PH 09448 COMPLETEC,'

SPECIFICATION

(ORIGINAL)

FOR OFFICE USE.

15168 Class Int. Class Application Nuib-cr: Lodgcd: Complete Specification Lodged', Accepted: Published: Priority-, 0 Related Art: I40 ,fl(86E10 Oli\\ S TWENTY DOLLAS TN OLR Name of Applicant(s): Adrs4f.plcn~) 44 -Address ofnApplorntss) TW& LIONS EYE INSTITUTE OF WESTERN AUSTRALLIA

INCORPORATED

2nd Floor 2 Verdun Street Nedliands

WA

AUSTRALIA

6009 MAXIMILIAAN JOSEPH HUBERTUS

CUYPERS

Address for Sezr'.ie Ke.vi-i1 Lord Co.~ 4 Douro Place, W-EST PER.TH, 'Western Australia 6005.

Cornptte Spccific,%tiofl for the invention en~titled', "MAGNIFYING BINOCULAR

OPHTHALMOSCOPE"

The following statement is a full description of this i nvention, including the best method of performning it known to mel us

'U

0 S I 49 00 9 0 9B 0 00 0 *i a oe #0 00 0 0400 00 0 00454 0 00 07a 4 P 2 The present invention relates to a magnifying binocular ophthalmoscope.

In accordance with one aspect of the present invention there is provided a magnifying binocular ophthalmoscope for use with an ophthalmoscopy lens to magnify an incoming image entering said ophthalmoscope, siad ophthalmoscope comprising: a light source housing containing a light source for illuminating the interior of a patient's eye; mirror means and two image reflecting means; said mirror means having two mirror units arranged to reflect said incoming image into two paths; each said image reflecting means being arranged to receive and reflect said incoming image from a respective said path; 15 each said image reflecting means reflecting said incoming image through a respective magnifying lens system comprising an objective lens, a Schmidt or Pechan prism means and an eye-piece through which an observer views a magnified incoming image, and each magnifying lens system has an optical axis; wherein, each said image reflecting means, objective lens, Schmidt or pechan prism means and eye-piece are linearly aligned whereby each said optical axis is a single non-deviating line extending from a respective said image reflecting means to a respective said eye-piece and whereby the said optical axes are substantially parallel.

The invention will now be described, by way of example, with reference to the accompanying drawings in which: Figure 1 is a perspective view of the magnifying binocular ophthalmoscope in accordance with the present invention, 2a with the casing cover removed therefrom; Figure 2 is a perspective view of schematic form showing the lens system of the magnifying binocular ophthalmoscope shown in Figure 1 in use with an ophthalmoscopy lens; Figure 3 is a schematic view of a magnification system, based on the Kepler telescopic system, for the magnifyine binocular ophthalmoscope of the present invention; and Figure 4 shows the forward and rear positions of the central mirror system and how they change the stereo base.

In Figure 1 there is shown a binocular magnifying ophthalmoscope 10 in accordance with one aspect of the present invention.

The magnifying binocular ophthalmoscope 10 comprises a support frame 12, substantially in the form of a plate, and optical components which are mounted on the support frame 12. A casing cover 14 normally covers the optical S! components. The cover 14 is attached to the support frame 12 by way of screws (not shown) engaging in the apertures 16, of the cover 14, and the apertures 18, of the support 9 9 f0 09 4 0 44 0

(VIVS

3 frame 12.

The cover 14 is provided with a centrally located lens 19 in its front wall.

The lens 19 is preferably a plano-convex lens.

The support frame 12 carries a central mirror system having a pair of mirrors The reflective face of each mirror 20 is positioned at an angle of 1350 to the optical axis 60 of the magnifying binocular ophthalmoscope 10 and at substantially a right anlge to each other. This is best seen in Figure 2. The support frame 12 has a pair of tubes 22 mounted thereon.

Each of the tubes 22 has an aperture 24 in its side wall.

An image reflecting means, such as a mirror 26, is mounted in each of the tubes 22. Each of the mirrors 26 has its reflective face opposed to the reflective face of the nearer one of the two mirrors 20. Further, each mirror 26 is i t a mounted such that its reflective face is parallel to the 1o reflective face of its opposed mirror S o Thus, the reflective face of each mirror 26 is positioned at an anye of 450 to the optical axis 60 of the magnifying binocular ophthalmoscope A 0 Each mirror 26 is mounted in its respective tube 22 such that its angle of rotation is adjsutable. Thus, in the event that a mirror 26 becomes misaligned, realignment 25 thereof is possible.

o A 00. The central mirror system comprising the mirrors 20 is movable over a short distance, e.g. about 3mm, in a direction parallel to the optical axis 60 of the magnifying binocular ophthalmoscope 10. This may be done by pushing or

MIF

4 S-4 pulling the knob 44 of the shaft 46. This alters the length of the stereo base of the magnifying binocular ophthalmoscope This can be seen in Figure 4, in which the central mirror system is shown in its forward position by solid lines and in its rear position by the broken lines.

In the forward position of the central mirror system the stereo base S.B.1. is longer than the stereo base S.B.2. in the rear position of the central mirror system.

Each of the tubes 22 contains the magnification system of the magnifying binocular ophthalmoscope 0 00 The magnification system may comprise a Kepler telescopic system.

0 0 The Kepler system is preferred over other telescopic systems, e.g. the Galilean, because it is able to achieve SO, higher magnification of good quality, which is more distinct in the peripheral field of view, compared with, for example, 0 0 the Galilean system. This is due, essentially, to the position of the exit pupil. (The exit pupil is the image of 0..0 20 the objective lens projected through the eye-piece, in a otelescopic system).

In the Kepler system, the exit pupil is projected in the pupil of the observer's eye. In the Galilean system, however, the exit pupil is projected somewhere in the middle of the lens system, away from the observer's eye.

Whilst the Kepler system is a longer telescopic system and also has an inverted image, these problems can be overcome by the use of a Schmidt or Pechan Prism.

A Kepler magnification system, suitable for the magnifying.

I I_ 5 binocular ophthalmoscope 10, is shown in Figure 3.

The magnification systems each comprise an objective lens 28, an eye-piece 34 and a Schmidt or Pechan Prism 42.

The objective lens 28 may comprise a cemented achromatic doublet composed of a positive crown glass element 30 and a negative flint glass element 32. Each element 30 and 32 would cancel the other's chromatic aberration.

The eye-piece 34, located at the end of each tube 22 remote from the mirrors 26, may comprise a cemented achromatic doublet composed of a positive crown glass element 36 and a negative flint glass element 38 in combiantion with an asymmetric bi-convex lens of crown glass A Schmidt or Pechan Prism 42 is located intermediate the objective lens 28 and the eye-piece 34. The Schmidt or 0 15 Pechan Prism 42 will shorten the length of the Kepler a telescope by "folding" the rays of light within the prism 42 a -0 Q 0 0 O and will, at the same time, cause a re-inversion of the 0Q 0 a o o, image without interfering with the optical axis. This can be seen in Figure 3.

Each of the tubes 22 is provided with a rotatable collar 48 to enable its eye-piece 34 to be rotated to compensate for O"0o ametropia in the observer. (The collar 48 is rotated clockwise to compensate for myopia, and counter-clockwise to 0 a comepnsate for hypermetropia).

Each magnification system has an optical axis indicated by o 4 00 C the broken lines 69 in Figure 2. The objective lens 28, eye-piece 34 and Schmidt or Pechan Prism are linearly aligned whereby each optical axis 69 is a single non-deviating line which extends froit a respective mirror 26 ,f I to a respective eye-piece 34. The optical axes 69 are substantially parallel. This is also seen in Figure 2.

The support frame 12 may also carry a light source housing 52. A light source, such as a 6 volt/10 watt halogen lamp, may be housed in the housing 52. The lamp is connected to a power source (not shown) via cable 62. The power source is clipped or otherwise attached to some part of the clothing, e.g. a belt, of the operator of the magnifying binocular ophthalmoscope To effectively concentrate light from the source, a i2tl I 0 -6 hemispherical reflector (not shown) may be mounted at the rear of the light source in the housing 52. The hemispheric-:l reflector is arranged such that heat and light is re~flected away from the operator.

To insulate the magnifying binocular ophthalmoscope 10 from heat conducted by the lamp hQusing 52, a laminated tufnol laye~: 54 may be positioned between the lamp housing 52 and the frame 12 of the magnifying binocular ophthalmoscope (The shaft 46 used for altering the stereo base extends into a 664 10 the laminated layer 54 and is connected to the central o 00mirror system comprising the mirrors 20. The layer may be of 3.1mm thickness).

6 .4 A single plano-convex condensing lens 56 is positioned at th3 'front of the light source.

The optical axis of the light source housing 52 is situated 4 parallel to, arid above, the optical axis 60 of the magnifying binocular ophthalmoscope A prism (not shown) may be incorporated in the condensing lens 56 to direct the ill.umination beam from the higher disposed light source housing 5? to the lower disposed level o of the optical axis 60. The illmination beam will then be refracted downwards by this prism to intersect the optical axis To reduce tbcs discomfort and danger of concentration of light and infra-red radiation in the anterior patt and retina of the patient's eye, an infra-red absorption filter may be placed between the light source in the light source housing 52 and the condensing lefts 56.

The magnifying binocular ophthalmoscope 10 may be mounted on i 7 a frame, such as a conventional spectacles type frame, by way of a ball-joint. The ball-joint would enable the magnifying binocular ophthalmoscope 10 to be properly aljusted in front of the operators eyes.

In use, the magnifying binocular ophthalmoscope 10 is used with an ophthalmoscopy lens 64, as shown in Figure 2. The light source in the light source housing 52 is energized and directed into the pupil of the eye 66 of the patient.

An ophthalmoscopy lens 64 is placed in front of the eye 66 10 of a patient. The ophthalmoscopy lens 64 produces an 0 aerial image 68 of the retina of the eye 66.

So An observer, i.e. the operator of the magnifying binocular C 0 So ophthalmoscope 10, then uses the magnifying binocular ophthalmoscope 10 to view and magnify the aerial image 68.

o. 15 The distance of the observer's eyes 70 to the ophthalmoscopy o0909 lens 64 will depend upon the power of the ophthalmoscopy lens 64, but would generally be in the range of 25cm to 0 a To achieve binocular observation of a patient's retina, it 20 is necessary that the placement of the image of the light 0 0 source, in the light source housing 52, and the placement of the apertures of the telescopic system are within the pupil Sof the eye. 66 of the patient.

Figure 2 shows the light paths 72 from the retina of a patient's eye 66.

The light paths 72 pass through the lens 19 and strike the mirrors 20 of the central mirror system and are reflected onto the mirrors 26. The focal point of the lens 19 will approximately coincide with aerial image 68. From the 8 mirrors 26, the light paths 72 pass through the telescopic system of the magnifying binocular ophthalmoscope 10. The observer's eyes 70 are placed adjacent the eye-pieces 34 and view a magnified aerial image 68.

The ability to alter the stereo base, by way of the knob 44 carried on the end of shaft 46, is particularly useful for observing the patient's peripheral retina.

When the patient looks to the left or to the right, his pupil appears as a vertically elongated oval, i.e. of elliptical shape, to the observer. The viewing and illuminating beams of the magnifying binocular ophthalmoscope 10 must fit within the elliptical shape of tne patient's pupil.

If the patient looks to the left or to the right, to allow the observer a view of the 3 o'clock and 9 o'clock peripheral retina, it will be easier for both apertures of the viewing beams to pass through the smaller elliptical pupil shape by bringing both apertures closer together, and decreasing the stereopsis angle. This is done by pushing in the knob 44, Thi. position is shown in Figure 4 in broken lines with the stereo base being S.B.I.

In viewing the 6 o'clock and 9 o'clock peripheral retina, however, the pupil becomes horizontally elongated, and the images of both viewing and illuminating beams will not fit within this shape. In this case, indirect binocular ophthalmoscopy of the peripheral retina is much facilitated if the patient is reclined and looking upward, and the observer can then move around th patient, and is able to position himself to obtain the best peripheral view.

I i 9 Preferably, the stereo base S.B.1. is 14mm and the stereo base S.B.2. is 8mm, with the distance D between the forward and rear positions of the central mirror system being 3mm.

The stereo base S.B.2. of 8mm is determined by the diameter of the objective lens 28. The stereo base S.B,2. cannot be smaller than the diameter of the objective lens 28. Any attempt to reduce the stereo base S.B.2. will result in the apertures of both telescopic systems interfering with each other, and the field of view will be cut off by the central 10 mirror system.

The field of view of the magnifying binocular ophthalmoscope 0 00 C a 10 should be somewhat larger than the diameter of the ophthalmoscopy lens 64, This allows for flexibility in the alignment of the magnifying binocular ophthalmoscope 10 and 15 the ophthalmoscopy lens 64. Additionally, it allows the So observer some field to move around in.

An example of suitable powers for the lenses of the 0 o magnifying binocular ophthalmoscope 10 follows.

The piano-convex lens 19 has a power of +3.0 dioptres.

.o.0 20 The achromatic doublet 28 may have a total combined power of +32 dioptres and a lens aperture, i.e. diameter, of 8mm, The total power of the eye-piece 34 may be +88 dioptres with a lens aperture of 12mm.

The magnification at infinity of such a telescopic system is given by: +88 MAGNIFICATION 2.7 +32 10 8mm DIAMETER OF EXIT PUPIL 2. 9m 2.75 The pupil diameter of the observer's eye 70 should always be 4larger than 2.9mm, to experience optimur, brightness of the telescopic system of the magnifying binocular ophthalmoscope The telescopic system of the magnifying binocular ophthalmoscope 10 is not used at infinity but at a worldng distance of 25-40cm, the distance at which the aerial. image 6a3 is observed.

AdjustMenit of the telescopic system of the magnifying binocular ophthalmtoscope 10 at a shorter worleing distance may be achieved by turning out the, qpllar4 48, carrying the l1 eye-pieces 34, which increases the cdLstanc between the objective lens 28 and the eye-piece 34.

In order fo-, the telescopic system of the magnifying binocu~lar ophthalmoscope 10 to focus at an o(rjaj image 68t that is located 25QM in front of the objective lens 78t 4 dioptros should be deducted from the power of' the cbj(octiW, lens 28t leaving a power of 28 dioptres.

The magnification at a 2$cni working distance, is given byt +88 KAGNIVIOA~TIN 3. 34 +24 since O25cm ia the working distance to Which magnitfication is normally comparecd, noe further magnification Is added.

In order fov thd telescopic .,.ystom al the~ m~a,,ifyinq binocular ophthaImoscepa A0 to focus at art gertal imaga GO 11 that is located 40cm in front of the objective lens 28, dioptres should be deducted from the power of the objective lens, leaving a power of 29.5 dioptres.

The magnification at a 40cm working distance is given by: a 5 +88 MAGNIFICATION 2.98 29.5 Since 25cm is the working distance to which magnification is normally compared, a magnification correction of 25cm/40cm 0.625 is applicable, leaving a total magnifiction at 0.625 x 2.98 1.86, The condensing lens 56 may have a power of +40 dioptres and o a diameter of The present invention allows for enhanced viewing of a patient's retina by an observer, such as an ophthalmologist, by providing a magnification of the aerial image of the retina produced by an ophthalmoscopy lens.

Moedifications arnd variations such as would be apparent to a skilled addressee are deemed within the scope of the present invention.

Claims

1. A magnifying binocular ophthalmoscope for use with an ophthalmoscopy lens to magnify an incoming image entering said ophthalmoscope, siad ophthalmoscope comprising: a light source housing containing a light source for illuminating the interior of a patient's eye; mirror means and two image reflecting means; said mirror means having two mirror units arranged to reflect said incoming image into two paths; each said image reflecting means being arranged to receive and reflect said incoming image from a respective said path; each said image reflecting means reflecting said incoming image through a respective magnifying lens system comprising an objective lens, a Schmidt or Pechan prism means and an 15 eye-piece through which an observer views a magnified incoming image, and each magnifying lens system has an optical axis; wherein, each said image reflecting means, objective lens, Schmidt or pechan prism means and eye-piece are linearly aligned whereby each said optical axis is a single non-deviating line extending from a respective said image reflecting means to a respective said eye-piece and whereby the said optical axes are substantially parallel.

2. A magnifying binocular ophthalmoscope in accordance with Claim 1, wherein said Schmidt or Pechan prism means is located between said objective lens and said eye-piece.

3. A magnifying binocular ophthalmoscope in accordance with Claim 1 or 2, wherein said two image reflecting means comprise two further mirror units.

4. A magnifying binocular ophthalmoscope in accordance r I- -II I- 13 0 io S. P Sg S as 00 *s 9 55d o 0o S S *055 I S 4rP 4555 55 SO with any one of Claims 1 to 3, wherein said two mirror units of said mirror means are at substantially a right angle to one another and a plano-convex lens is positioned forward of said mirror means such that said incoming image is refracted by said plano-convex lens prior to said incoming image impinging upon said two mirror units of said mirror meann.

A magnifying binocular ophthalmoscope in accordance with any one of Claims 1 to 4, further comprising means to alter the stereo base of said magnifying binocular ophthalmoscope.

6. A magnifying binocular ophthalmoscope in accordance with Claim 5, wherein said means to alter the stereo base comprises a movable shaft means connected to the said mirror means such that said mirror means is movable between a first 15 forward position and a second rear position.

7. A magnifying binocular ophthalmoscope in accordance with any one of Claims 1 to 6, the beam of said light source is refracted from said light source housing such that it intersects the optical &xis of the said magnifying binocular ophthalmoscope.

8. A magnifying binocular ophthalmoscope in accordance with Claim 7, wherein said light source housing is provided with reflector means arranged to reflect light and heat from said light source out of said light source housing.

9. A magnifying binocular ophthalmoscope in accordance with any one of Claims 1 to 8, wherein each of said magnifying lens systems comprises a Kepler telescopic system.

A magnifying binocular ophthalmoscope in accordance 14 with any one of Claims 1 to 9, wherein each said objective lens comprises a cemented achromatic doublet composed of a positive crown glass element and a negative flint glass element and each said eye-piece comprises a cemented achromatic doublet composed of a positive crown glass element and a negative flint glass element in combination with an asymmetric bi-convex lens of crown glass.

11. A magnifying binocular ophthalmoscope according to any one of the preceding Claims, wherein said mii7ror means and said magnifying lens systems are mounted on a support frame and covered by a casing cover.

12. A magnifying binocular ophthalmoscope substantially as hereinbefore described with reference to the accompanying drawings. DATED JUNE 24 1991 THE LIONS EYE INSTITUTE OF WESTERN AUSTRALIA INCORPORATED By their Patent Attorneys KELVIN LORD AND COMPANY PERTH, WESTERN AUSTRALIA. t i 1,v