GB2123977A - Ophthalmic test apparatus - Google Patents
Ophthalmic test apparatus Download PDFInfo
- Publication number
- GB2123977A GB2123977A GB08317121A GB8317121A GB2123977A GB 2123977 A GB2123977 A GB 2123977A GB 08317121 A GB08317121 A GB 08317121A GB 8317121 A GB8317121 A GB 8317121A GB 2123977 A GB2123977 A GB 2123977A
- Authority
- GB
- United Kingdom
- Prior art keywords
- cornea
- bowl
- geometric pattern
- hemi
- pattern
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
Classifications
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B3/00—Apparatus for testing the eyes; Instruments for examining the eyes
- A61B3/10—Objective types, i.e. instruments for examining the eyes independent of the patients' perceptions or reactions
- A61B3/101—Objective types, i.e. instruments for examining the eyes independent of the patients' perceptions or reactions for examining the tear film
Abstract
An ophthalmic apparatus adapted to project the image of a rectangular geometric pattern onto the cornea of an eye comprises a hemi-spherical bowl 1 which has on one of its surfaces, preferably on the inside surface 2, a geometric pattern which when projected onto a cornea and viewed as a reflected image appears as a rectangular geometric pattern. Preferably the pattern is projected onto the cornea using an illuminating means 3 positioned around the circumference of the bowl and the reflected image is viewed using a microscope 6 positioned at the apex 5 of the bowl. The apparatus is used as a non-invasive means of measuring tear film break-up time, for observing distortions in the cornea either diagnostically or following surgery and the rectangular pattern may be calibrated and parameters of the cornea derived. <IMAGE>
Description
SPECIFICATION
Ophthalmic test apparatus
The present invention relates to an ophthalmic test apparatus which is adapted to project a geometric pattern onto the surface of the cornea of the eye whereby the break-up of the tear film covering the cornea of the eye and abnormalities in the shape of the cornea may be observed by viewing the distortions caused in the said geometric pattern and has a means for observing these distortions by collecting the light reflected from the cornea. The present invention also relates to a method for measuring the break-up time of the tear film on the cornea using such an apparatus.
Some individuals are unable to produce sufficient tears to form a normal tear film over the cornea of the eye. In such so-called 'dry-eye' conditions the tear film breaks up and drains away within a short period of formation. This condition can cause irritation, discomfort, inflammation and profound damage to the cornea.
The treatment of choice is frequent instillation of a buffered, isotonic aqueous solution containing hydrophilic polymers. However, the diagnosis of the condition and the efficacy of the treatment has previously been difficult to measure. One method frequently used is the Schirmer test in which one end of a dry strip of filter paper is inserted into the conjuctival sac and the rate of wicking of tears from the eye is measured. This method is not totally satisfactory in measuring tear deficiency as the dry paper may be irritant and cause excessive tearing and so give an abnormally high reading. A second method is to instil an aqueous solution of sodium fluorescein into the eye. The tear film is viewed using a slit-lamp microscope under cobalt blue light. The fluorescent tear film is allowed to break up over the cornea in the absence of blinking.The initiation of tear film break-up is shown by the appearance of black spots in the fluorescing tear film. This method is unsatisfactory in that it is not always reproducible and the sodium fluorescein solution often contains a surface active agent which effects the tear film stability. A non-invasive method has been suggested whereby a grid pattern is projected onto the cornea using a mirror galvanometer projector and its reflection from the tear film observed with a slit-lamp microscope. Provided the tear film is intact the reflected image of the grid pattern is undistorted but as soon as the film begins to break up distortion is apparent in the image. This method provides a non-invasive, reproducible means of measuring tear film break up time and the efficacy of artificial tear solutions in vivo.However, this apparatus has the disadvantage that the grid pattern does not cover the entire cornea and it may not form a distinct image. The apparatus of the present invention overcomes these disadvantages by providing a clear, distinct image which covers the entire cornea. The apparatus is compact, easily manufactured, simple to use, non-invasive and gives more reproducible results as compared to previously used methods.
The use of the apparatus of the present invention is particularly advantageous after cataract removal, corneal grafting and such corneal operations to observe the progress of healing. A particularly serious complication is the presence of stress around the corneal graft or at the point of suture eg. in corneal grafts.
The apparatus of the present invention provides a particularly effective means to recognise the presence of stress in the cornea by observing the presence of distortions in the image of the geometric pattern projected onto the cornea.
Other corneal abnormalities will similarly cause distortion in the image. Such abnormalities include
Keratoconus, Dellen and astigmatism and the like. The apparatus of the present invention can be used in the diagnosis of these conditions and as such is particularly useful in the diagnosis of corneal astigmatism which aids in the correct fitting of contact lenses.
In yet a further aspect the apparatus of the present invention may be used in the measurement of corneal curvature prior to fitting contact lenses, for example where a good fit is essential for acceptable visual acuity.
The rectangular pattern may be calibrated and the parameters of the cornea derived.
Accordingly, in a first aspect the present invention provides an ophthalmic apparatus adapted to project the image of a rectangular geometric pattern onto the cornea of an eye which apparatus comprises a hemi-spherical bowl having present on one surface thereof a geometric pattern which when projected onto the cornea and viewed as a reflected image appears as a rectangular geometric pattern on the cornea.
From the foregoing it is clear that the present invention comprises an ophthalmic apparatus adapted to project the image of a geometric pattern onto the cornea of the eye which apparatus comprises a hemi-spherical bowl having present on one surface thereof a geometric pattern characterised in that the geometric pattern when projected onto the cornea and viewed as a reflected image appears as a rectangular geometric pattern on the cornea.
Suitably the geometric pattern is present on only one surface of the hemi-spherical bowl. The pattern appears in the form of intersecting lines such that at and near to the apex of the bowl they intersect at right angles whilst further from the apex they intersect so as to form diamond or parallelogram shapes so that when the pattern is projected onto the cornea and viewed in reflection from the surface of the cornea the pattern appears as a rectangular grid and preferably as a square grid. Similarly narrow lines are present at or near to the apex, having a width of 0.75 to 1 .25mm for example 1 mm, but become thicker as they near the edge of the bowl whereby the thickness of the lines at the edge of the bowl is 4.5 to 6.0mm for example 4.8mm. This means that after projection onto the cornea the lines appear as having equal thickness.
The material which forms the hemi-spherical bowl may be translucent or opaque. A translucent bowl may be made from glass or a plastic material. Using such a translucent bowl the geometric pattern is suitably present on the outer surface of the bowl. An illuminating means is placed behind the bowl, that is on the same side of the bowl as the observer and the light is transmitted through the unmasked lines on the outside of the bowl and projects an image of the pattern onto the cornea.
It is preferred, however, to employ a hemi-spherical bowl which is opaque. An opaque bowl is conventionally made from metal. Using such an opaque bowl the geometric pattern is suitably present on the inner surface of the bowl. An illuminating means is placed in front of the bowl that is on the same side of the bowl as the subject under investigation. Preferably the illuminating means is arranged around the circumference of the bowl whereby the light is directed into the bowl. The illuminating means may extend over only part of the circumference of the bowl but is most preferably in the form of a circular fluorescent tube, for example a cold fluorescent tube. The diameter of the circular tube is approximately the same as that of the bowl.The illuminating means is suitably surrounded on three sides by a protector which serves to prevent damage to the tube and to prevent accidental contact with the subject. The geometric pattern will be present as white lines on a dark matt background. Preferably the background is black.
The illuminating means is most suitably a white light thereby giving white lines, however coloured light may be used if appropriate.
The white lines of the geometric pattern may be formed on the surface of the hemi-spherical bowl which is coated with a white fluorescent material by drawing the pattern of the bowl with the lines showing the required variation in width, placing masking tape over the lines, spraying the remainder of the surface with a material to give a dark matt finish and finally removing the tape to leave white lines in the correct geometric pattern and having the correct thickness. In consequence the surface of the lines so re-exposed is fluorescent thereby providing a clear distinct white grid on the surface of the cornea.
Alternatively the lines may be formed as a pre-formed mesh and placed and adhered within or around the hemispherical bowl as appropriate. In a further method the lines may be formed by a photographic or lithographic method which would include subsequent painting or etching techniques.
Alternatively the pattern may be of black lines on a white background in which the pattern may be simply painted onto a white hemispherical bowl.
The hemispherical bowl has at its apex a hole through which the image of the geometric pattern on the cornea is viewed. Suitably the bowl is attached to the microscope so that the objective lens is at the apex of the bowl. The bowl is attached to a microscope conventionally used with a slit-lamp apparatus enabling movement both vertically and horizontally of the bowl and microscope so that they can be positioned exactly whereby the geometric pattern falls on the cornea at the focal point of the microscope, thereby providing a clear sharp image of the pattern over the entire cornea. A suitable movable microscope system is available from Zeiss as the Zeiss Slit-Lamp Biomicroscope.Clearly in this type of apparatus of the present invention it is important that the head of the patient remains fixed as the position of the microscope is altered, a chin rest is preferably present in the apparatus.
It is preferred that the chin rest is movable in a vertical plane so that a preliminary coarse adjustment to the subjects head may be made prior to accurate positioning using the movable microscope and bowl.
It is a further advantage of the apparatus of the present invention that a binocular microscope may be used. This allows the image of the geometric pattern on the cornea to be observed dimensionally which is particularly advantageous when looking at stress patterns in the cornea.
The size of the hemisphere is such as to be capable of surrounding the head of the patient should the focal length of objective lens of the microscope be less than the radius of the hemi-spherical bowl. Suitably the hemi-spherical bowl will have a radius of from 100mm to 1000mm, more suitably 100mum to 300mm and preferably 1 50mm to 250mm. Preferably the focal length of the objective lens of the microscope is approximately the same as the radius of the bowl.
From the foregoing it is clear that in a further aspect the present invention provides an ophthalmic apparatus adapted to project the image of a rectangular geometric pattern onto the cornea of the eye which apparatus comprises a hemi-spherical bowl having present on surface thereof a geometric pattern and an illuminating means for that pattern such that the pattern when illuminated is projected onto the cornea appears as a rectangular geometric pattern on the cornea.
In a further aspect therefore the present invention provides an ophthalmic apparatus adapted to project the image of a rectangular geometric pattern onto the cornea of the eye which apparatus comprises a hemi-spherical bowl having on one surface thereof a geometric pattern which when projected onto the cornea provides rectangular geometric pattern, an illuminating means for projecting said pattern onto the cornea, a microscope positioned at the apex of the hemi-spherical bowl to observe the image of said pattern reflected from the cornea and a head rest for holding the cornea in a fixed position.
The preferred embodiment of the invention is now described with reference to the accompanying drawings in which,
Figure 1 is a schematic cross-section of the assembled apparatus
Figure 2 is a view along the radius of the hemi-spherical bowl looking towards the apex
In Figure 1 the hemi-spherical bowl (1) has present on its inside surface (2) a geometric pattern which when illuminated by the illuminating means (3) projects an image of that pattern onto the cornea of the eye.
The illuminating means (3) is a circular fluorescent tube which is surrounded on three sides by a protector (4) attached to and around the rim of the hemi-spherical bowl (1). The apex of the bowl (5) is removed so that the bowl may be attached to the objective lens part of a slit lamp microscope (6). The bowl is held between the microscope (6) and a fitting which screws into the microscope which also holds the objective lens of the microscope. The objective of the microscope is positioned at the apex of the bowl (1). As a result the bowl (1), microscope (6) and stand (8) are able to move as a single unit in any direction in the horizontal plane as well as vertically as is conventional with a slit-lamp-type apparatus.This movement enables the focal point of the objective lens and the cornea to be made to coincide thereby providing a clear and distinct image of the pattern to the observer. The head of the subject is held stationary relative to the observer by means of the chin rest (9). In use the subject's chin is placed on the chin rest and remains stationary whilst the microscope (6) and bowl (1 ) are moved as a single unit until a clear image of the geometric pattern is observed on the cornea of the patient.
Figure 2 shows the geometric pattern of intersecting lines on the inside of the hemispherical bowl (1 ) as~it would appear to the observer. The allowance made for perspective in the hemispherical nature of the bowl shows the pattern appearing as a rectangular grid.
The use of the apparatus of the present invention to measure tear film break-up time may be performed as follows, the subject is placed before the apparatus with his chin resting on the chin rest, the height of the chin rest is adjusted so that the cornea is at the same height as the microscope. The illumination is switched on and the microscope with bowl attached is manoeuvred until a sharp image of the pattern on the bowl is observed on the cornea through the microscope. During this period the subject is allowed to blink so that his normal tear film is present. Having adjusted the apparatus the subject is requested not to blink and the rectangular pattern on the cornea observed. As the tear film thins and breaks up it reaches a point at which it is no longer continuously covering the cornea.At this point a distortion or irregularity becomes readily apparent in the pattern on the cornea. The time taken from the last blink to the observation of the distortion in the pattern is known as the tear film break-up time. In normal subjects the time is of the order 20-25 seconds whilst in subjects who are deficient in tears the time is reduced and often less than 10 seconds.
Clearly if an artificial tear solution is instilled into the eye, the tear film break-up time should be lengthened and this may be measured directly using this apparatus.
Thus the present invention also provides a method of measuring tear film break-up time by observing the time taken for the image of a rectangular geometric pattern on the cornea to become irregular using an apparatus hereinbefore described.
From the foregoing it is clear that in a further aspect the present invention comprises a non-invasice method of measuring tear film break-up time characterised in that the method comprises observing the time taken for the image of a rectangular pattern projected onto the cornea to become irregular, said rectangular geometric pattern being formed using an ophthalmic apparatus comprising a hemi-spherical bowl having present on one surface thereof a geometric pattern which when projected onto the cornea and viewed as a reflected image appears as a rectangular geometric pattern.
It is possible using a conventional attachment on the slit lamp microscope to photograph the image of rectangular image on the surface of the cornea.
Demonstration of Effectiveness
The advantage of using the apparatus of the present invention as a non-invasive means of measuring tear film break-up time as compared to the previously known conventional method of instilling fluorescein solution into the eye was demonstrated as follows. The fear film break-up time was measured in none healthy volunteers with no history of ocular pathology by observing the distortion of a rectangular geometric pattern projected onto the cornea by the apparatus of the present invention. This measurement was taken at intervals over a period of 15 minutes to enable a comparison with a fluorescein treated tear film to be made.
In the fluorescein treated tear film a drop of fluorescein solution was administered to the eye and the tear film break-up time measured using a slit lamp and illuminating the cornea with a blue light. Thetearfilm break-up time was measured at intervals 0-2 minutes, 3-5 minutes and 10-15 minutes post treatment.
The results were as follows for the tear film break-up time (secs.).
Time interval Non-invasive Fluorescein
method Instillation
Method
Pretreatment (baseline) 27.9 27.7
0-2 mins post treatment 28.0 20.6
3-5 mins post treatment 26.3 21.4
10-15 mins post treatment 29.2 28.4
The results show a significant fail in tear film stability after treatment with fluorescein in the treated eye.
Claims (19)
1. An ophthalmic apparatus adapted to project the image of a rectangular geometric pattern onto the cornea of an eye which apparatus comprises a hemi-spherical bowl having present on one surface thereof a geometric pattern which when projected onto the cornea and viewed as a reflected image appears as a rectangular geometric pattern on the cornea.
2. An ophthalmic apparatus as claimed in claim 1 in which the hemi-spherical bowl is made from a translucent material whereby the geometric pattern is present on the outside of the bowl.
3. An ophthalmic apparatus as claimed in claim 1 in which the hemi-spherical bowl is made from an opaque material whereby the geometric pattern is present on the inside of the bowl.
4. An ophthalmic apparatus as claimed in claim 3 in which the hemi-spherical bowl has an illuminating means arranged around the circumference of the bowl.
5. An ophthalmic apparatus as claimed in claim 4 in which the illuminating means comprises a circular fluorescent tube.
6. An ophthalmic apparatus as claimed in any of claims 1 to Sin which the geometric pattern is present as a pattern of white lines on a dark matt background whereby the reflected image appears as a white rectangular geometric pattern on the cornea.
7. An ophthalmic apparatus as claimed in any of claims 1 to 6 in which the hemi-spherical bowl has at its apex a hole through which the reflected image of the rectangular geometric pattern projected onto the cornea may be viewed.
8. An ophthalmic apparatus as claimed in any of claims 1 to 7 in which the diameter of the bowl is from 10to30cm.
9. An ophthalmic apparatus adapted to project the image of a rectangular geometric pattern onto the cornea of the eye which apparatus comprises a hemi-spherical having on one surface thereof a geometric pattern which when projected onto the cornea provides a rectangular geometric pattern, a microscope positioned at the apex of the hemi-spherical bowl to observe the image of said pattern reflected from the cornea and a head rest for holding the cornea in a fixed position relative to the microscope.
10. An ophthalmic apparatus as claimed in claim 9 in which the hemi-spherical bowl, illuminating means and microscope are positionable with relation to the surface of the cornea so that the surface of the cornea coincides with the focal length of the lens of the microscope.
11. A non-invasive method of measuring tear film break-up time characterised in that the method comprises observing the time taken for the image of a rectangular geometric pattern projected onto the cornea to become irregular, said rectangular pattern projected onto the cornea to become irregular said rectangular pattern being formed using an ophthalmic apparatus comprising a hemi-spherical bowl having present on one surface thereof a geometric pattern which when projected onto the cornea and viewed as a reflective image appears as a rectangular geometric pattern.
12. A method according to claim 11 in which the hemi-spherical bowl is made from a translucent material whereby the geometric pattern is present on the outside of the bowl.
13. A method according to claim 11 in which the hemi-spherical bowl is made from an opaque material whereby the geometric pattern is present on the inside of the bowl.
14. A method according to claim 13 in which the hemi-spherical bowl has an illuminating means arranged around the circumference of the bowl.
15. A method according to claim 14 in which the illuminating means comprises a circular fluorescent tube.
16. A method according to claim 11 in which the geometric pattern is present as a pattern of white lines on a dark matt background whereby the reflected image appears as a white rectangular geometric pattern on the cornea.
17. A method according to claim 11 in which the hemi-spherical bowl has at its apex a hole through which the reflected image of the rectangular geometric pattern projected onto the cornea may be viewed.
18. A method according to claim 11 in which the hemi-spherical bowl has a diameter of from 10 to 30cm.
19. A method according to claim 17 in which the image is viewed through the hole in the apex of the hemi-spherical bowl using a microscope.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB08317121A GB2123977B (en) | 1982-07-03 | 1983-06-23 | Ophthalmic test apparatus |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8219304 | 1982-07-03 | ||
| GB08317121A GB2123977B (en) | 1982-07-03 | 1983-06-23 | Ophthalmic test apparatus |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| GB8317121D0 GB8317121D0 (en) | 1983-07-27 |
| GB2123977A true GB2123977A (en) | 1984-02-08 |
| GB2123977B GB2123977B (en) | 1986-04-16 |
Family
ID=26283252
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB08317121A Expired GB2123977B (en) | 1982-07-03 | 1983-06-23 | Ophthalmic test apparatus |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2123977B (en) |
Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2604618A1 (en) * | 1986-10-07 | 1988-04-08 | Caubet Emmanuel | Device allowing instantaneous measurement of the volume of tears |
| WO1992012666A1 (en) * | 1991-01-23 | 1992-08-06 | Inge Muster | Device for analysing the lachrymal film |
| WO1993024049A1 (en) * | 1992-06-02 | 1993-12-09 | Eyesys Laboratories | Checkered placido apparatus and method |
| US5841511A (en) * | 1992-06-02 | 1998-11-24 | Eyesys Technologies, Inc. | Method of corneal analysis using a checkered placido apparatus |
| EP0943288A1 (en) * | 1998-03-20 | 1999-09-22 | Kowa Company Ltd. | Ophthalmic apparatus |
| EP1509122A1 (en) * | 2002-05-08 | 2005-03-02 | Lions Eye Institute Limited | Imaging apparatus and adaptors therefor |
| US8613516B2 (en) | 2010-05-27 | 2013-12-24 | Gianfranco Passuello | Ophthalmic illumination device |
| CN115991324A (en) * | 2023-03-24 | 2023-04-21 | 成都斯马特科技有限公司 | Release paper film tearing device and method |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB913872A (en) * | 1959-03-17 | 1962-12-28 | John Trevor De Carle | A device for measuring the curvature of the eye |
| GB1108304A (en) * | 1964-03-25 | 1968-04-03 | Guilbert Routit & Cie | Improvements in ophthalmometers |
| GB1286887A (en) * | 1970-10-12 | 1972-08-23 | Jessen Inc Wesley | Apparatus for determining corneal contour |
| GB1563286A (en) * | 1976-09-11 | 1980-03-26 | Battelle Institut E V | Devices for and methods of measuring the curvature of the cornea |
-
1983
- 1983-06-23 GB GB08317121A patent/GB2123977B/en not_active Expired
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB913872A (en) * | 1959-03-17 | 1962-12-28 | John Trevor De Carle | A device for measuring the curvature of the eye |
| GB1108304A (en) * | 1964-03-25 | 1968-04-03 | Guilbert Routit & Cie | Improvements in ophthalmometers |
| GB1286887A (en) * | 1970-10-12 | 1972-08-23 | Jessen Inc Wesley | Apparatus for determining corneal contour |
| GB1563286A (en) * | 1976-09-11 | 1980-03-26 | Battelle Institut E V | Devices for and methods of measuring the curvature of the cornea |
Cited By (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2604618A1 (en) * | 1986-10-07 | 1988-04-08 | Caubet Emmanuel | Device allowing instantaneous measurement of the volume of tears |
| WO1992012666A1 (en) * | 1991-01-23 | 1992-08-06 | Inge Muster | Device for analysing the lachrymal film |
| WO1993024049A1 (en) * | 1992-06-02 | 1993-12-09 | Eyesys Laboratories | Checkered placido apparatus and method |
| US5841511A (en) * | 1992-06-02 | 1998-11-24 | Eyesys Technologies, Inc. | Method of corneal analysis using a checkered placido apparatus |
| US6213605B1 (en) | 1992-06-02 | 2001-04-10 | Lasersight Technologies, Inc. | Method of corneal analysis using a checkered placido apparatus |
| EP0943288A1 (en) * | 1998-03-20 | 1999-09-22 | Kowa Company Ltd. | Ophthalmic apparatus |
| EP1509122A1 (en) * | 2002-05-08 | 2005-03-02 | Lions Eye Institute Limited | Imaging apparatus and adaptors therefor |
| EP1509122A4 (en) * | 2002-05-08 | 2008-04-30 | Lions Eye Inst Ltd | Imaging apparatus and adaptors therefor |
| US7986342B2 (en) | 2002-05-08 | 2011-07-26 | The Lions Eye Institute Limited | Multi-purpose imaging apparatus and adaptors therefor |
| US8613516B2 (en) | 2010-05-27 | 2013-12-24 | Gianfranco Passuello | Ophthalmic illumination device |
| CN115991324A (en) * | 2023-03-24 | 2023-04-21 | 成都斯马特科技有限公司 | Release paper film tearing device and method |
| CN115991324B (en) * | 2023-03-24 | 2023-08-04 | 成都斯马特科技有限公司 | Release paper film tearing device and method |
Also Published As
| Publication number | Publication date |
|---|---|
| GB8317121D0 (en) | 1983-07-27 |
| GB2123977B (en) | 1986-04-16 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PCNP | Patent ceased through non-payment of renewal fee |