DD269781A1 - ARRANGEMENT FOR MEASUREMENT ON EYE BACKGROUND - Google Patents

Abstract

The objective detection of fine pulsatile auto- or local regulation vasodilatory changes is made possible by one and the same image field in an arrangement for measurement on the ocular fundus, wherein a picture of the ocular fundus is made on a CCD line and an illumination beam path is provided for at least flashing illumination of the ocular fundus of the fundus is imaged onto at least two CCD line segments, means being provided for altering the image position and the optical properties of the image. figure

Description

For this 2 pages drawings

Field of application of the invention

The invention is applicable to the diagnosis of various circulatory flows of the retina, in particular the detection of vessel width changes.

-? - 269 781 Characteristic of the known technical solutions

The differential diagnosis of different circulatory disorders of the new skin requires not only the detection of relatively large patologischen Gefäßweitenänderi'ngcn (up to 30%), but also the small auto- or lokalregulatl · 'conditional vessel width changes, which may be less than 10%. Furthermore, in order to be able to assess the degree of vessel vascularity, it is necessary to detect pulsatile vessel width changes with a time resolution of 10 ms. For measuring vessel width at the fundus several measuring methods are known. They can be divided into dr A groups of principles of measurement:

1. Use of Optical Feinmeßtechnik in the ophthalmological image

2. Optical precision measuring technique and densitometry on the photographic negative ^,

3. Photoelectric measuring method

The measuring methods mentioned under 1. have the disadvantage that by the subjective measurement comparison considerable subjective Sources of error can occur. The ocular fundus is subject to a prolonged high exposure to the required lighting

exposed. For observers and patients this leads to fatigue.

Reproducibility, systematic Fr overruns and temporal resolution are inherently unsuitable, pulsatory or

to measure autologous regulatory vessel dilation with sufficient accuracy and temporal resolution.

The measuring methods of the 2nd group have the disadvantage of the temporal separation of examination and presence of the Measurement result. In addition, sources of error through the photographic process and a high apparatus and ze cally Expenditure. They are conditionally applicable for clinical-experimental questions in research, for the clinical f! Outine

but unsuitable.

PREUSSNER joined the 3rd group in 1985. ' rendes method for interactive image analysis of TV Fundusaufnahr, ien ago. The OiId dissolves the diameter of a large retinal vessel with about 3 pixels (geometric resolution about 30pm). The Image section with the vessel is enlarged electronically. The measuring line is set perpendicular to the vessel. Perpendicular to Measuring line, ie in the vessel direction, are set gap-shaped areas, determined by the average image brightness for each gap

and is applied over the measuring line. The gap width (perpendicular to the vessel) is defined with 0.1 fan pixel width and the gap length (in the vessel direction) with 10 times the pixel width. In the case of a slight tilt of the column assembly against the

Primary pixel arrangement (with a sufficiently high secondary magnification, the now small secondary pixels can be added as desired

be merged into a gap) is an interpolation effect with simultaneous averaging over the

Image noise and over the detected by the gap length vessel section. Because the gap length related to the large vessels

is about 3 to 5 times the diameter of the vessel, this method is particularly susceptible to inclinations

Unfavorable and substantial sources of error are the TV-related relatively high signal / interference ratio and the

relatively long image formation time in which that vessel can move within the image field in the direction of measurement and in this case causes erheblic.ie error. The time required for a measurement is large. The measurement temporal

GIOVANNINI and coworkers make changes in the vascular width as relative values to detect vascular pulsations of the vessels

the retina, the papilla head and at non-pigmented areas of the vessels of the choroid. This is in turn of a

TV recording and the brightness of measuring surfaces on the desired vessel sections are

recorded. (Video photo plethysmography)

In 1982, DELORI and co-workers introduce a vascular scanner that oscillates in an optical image plane over a vessel section.

(Amplitude 770μπι; gap width Ve of the vessel diameter, gap length - in Gefäßi direction - 5facher vessel diameter).

The current vessel position for each oscillation is determined and several oscillations are accumulated. (Since after the According to the authors a vibration needs 25ms, the signal of a vibration is already no longer free of Distortions that can be caused by involuntary eye movements.) Furthermore, it is known (Jenaer Rundschau 2/87, p. 7 & -78), by means of a CCD Zeila, in an image plane of a Measuring beam path is arranged to make a vessel representation and interactive vessel width measurement by by

a cursor is marked by the examiner's vascular edges.

The cited photoelectric measuring methods have the disadvantage that the vessel edges are not clearly defined Kai s, so

that the shape of the edge on the measurement error oinen has a significant influence that from recording to recording the

Change the illumination Verhälinisse and thereby also the edge shape and thus the measurement error is affected. At o.g. Process is achieved in the best case, a reproducibility of the vessel width of only 10%. By Eye movements during image acquisition or vascular scanning, it comes to Meßobjektverschiebungen that to a

can lead to additional uncontrollable systematic errors that can be significantly greater.

For the detection of locally regulative changes of the vessel size the reproducibility is not sufficient. In the scanner principle, an attempt is made to eliminate the errors caused by eye movements, each by the other

is shifted to superimposed signals before the superposition so that the local displacement of the vessels is reduced against each other. This is expensive and inaccurate equipment. In addition, one vial scanner needs 25ms per oscillation.

During this time, the vessel may well have moved from 20-3μum in the measuring direction, resulting in a non-controlled and

correctable systematic error that is already contained in the signal of a single oscillation.

All mentioned device solutions are currently for clinical use for the detection of small pulsatory,

Autolokalregulativer vascular width changes unsuitable.

Object of the invention

The aim of the invention is a device suitable for clinical use for vessel width measurement, which enables the objective detection of fine pulsatory, auto- or local regulatory changes in the vascular width.

-3- 269 781 Explanation of the nature of the invention

The object of the invention is to increase the reproducibility of a measurement while reducing uncontrollable systematic Fet er, the realization of a time resolution of 100ms without significant time lag between measurement and evaluation, with the least possible apparative> '»and.

Dio object is achieved in an arrangement for measuring the ocular fundus, wherein a picture of the ocular fundus on a CCD line and an illumination beam path for at least lightning shaped illumination of the ocular fundus is achieved in that one and the same field of view of the ocular fundus on at least two CCD Zeiienabschnitten is provided, wherein means for changing the image position and the optical properties of the image are provided.

In this case, the line segments can be components of one and the same CCD line, but also components of several CCD lines or the CCD lines themselves. It is particularly advantageous that the imaging beam path is partially split, that in the non-split part of the Abbildungsstrahlonganges a picture rotating unit is provided. in that at least in one of the split-up parts of the imaging beam path a image-rotating line is provided, wherein spectral and polarization filters can be provided.

Furthermore, it is advantageous that an object which is displaceable in the direction of the optical axis is provided, a prism which changes the beam direction and is tiltable about two axes. Continuous illumination is realized via the illumination beam path and an observation beam path is masked out of the imaging beam path.

The extension takes place via a pivoting deflection unit.

Furthermore, it is advantageous that are superimposed on a prism having a plurality of reflective surfaces, the Bildr> and its traceable to the CCD line brand arrangement in the observation beam path that a pivotable in the imaging beam path. Folding mirror is provided, which is replaced for the purpose of image recording by a partially transparent, rotated by 90 ° with respect to the Klaopspiegel mirror, the "splitting is provided as amplitude splitting beam splitter is replaced by a stereo beam splitter for wavefront division, that in the imaging beam path in the vicinity of the CCD Receiver an arrangement of crossed Zylindorlinsen is provided.

Surprisingly universal measuring possibilities are possible by the invention, for example for geometrical measurements on the ocular fundus (vessel width, diameter of the papillae, diameter of excavation, extent of tumors, growth processes), spectral examinations (papillae color, acquisition of option perfusion, blood volume of the retina, spectral change of optic nerve head o. Fundusbereiche, Tiefenprofilmessuny) given.

By projecting on two sections of a CCD line, it is possible to obtain simultaneously several independent signals from one object which are evaluated with regard to the spectral information, the geometric information (measuring location), 3-D detection and the degree of polarization.

With respect to the geometric information, there are several possibilities for the offset of line sections:

Parallel offset, parallel offset and transverse shift, transverse shift, skew). The parallel offset and the transverse displacement are realized by the tiltable prism, the rotation by image rotating units.

A transverse shift of half a pixel width allows for interpolation in the vessel width measurement. A shift by the length of the Zeilenabschniites causes an extension of the measuring range to twice.

In the case of parallel offset, the fundus object is recorded under different geometric locations, so that associated, different, disturbing reflection components can be detected.

For the fluorophotometry on a vessel section two measuring points for speed measurement or circulation time measurement (measuring point 1 on the artery, measuring point 2 associated vein) to be created.

In a combination of transversal and parallel displacements, Gofäßo gauges can be determined simultaneously in two different vessels.

A twisting of lines or lines against each other allows the Messuna the two-dimensional expansion of retinal objects, z. B. for Papillendiagnostik (excavation, Rinnzone), and the perfusion of the papilla, z. B. to detect leadership defects during the passage of a fluorescent indicator.

With spectrally different tuning of the split imaging paths, identical noise components result in exactly the same illumination conditions in terms of their amplitude and geometric position.

Using identical local line layers results in signal differences that depend only on the spectral reflectance properties of the image.

The spectral characteristics of the imaging beam paths are selected so that the medically relevant information is recognizable as a signal difference.

With the use of a stereo beam splitter, two signals are obtained, with an indent line position and suitable illumination, in which the parallax of identical pixels represents their position in the depth. Thus, depth profiles can be determined.

Furthermore, for the detection of regular reflection components, z. B. in the vessel width measurement, d> e Signalriifferenz be used with identical line length.

If the medically relevant information lies in the diffuse reflection light component, the regular reflection component can be switched off by using polarization filters with suitable illumination.

By displacing an objective in one of the split imaging beam paths, defocusing of an image produces a sharp and a blurred signal with which, in a known manner, an edge elevation and better edge detection, -. '? can be achieved with vessel width measurement.

A similar Wirku g can be achieved by changing the opening ratios of the split imaging beam paths.

By the inventive inclusion of the brand arrangement both in the observation and in the recording beam path all manipulations in the imaging beam paths can be kept under visual control odei registered in the recorded image. For an exact registration of the measuring locations and the measurement properties is possible.

embodiment

The invention will be explained in more detail below with reference to the schematic drawings.

A patient's eye 1 is illuminated by a Lochspiegol 4 and an ophthalmoscope lens 2 by means of a Beleuchtungsstruhengangei 6. An imaging beam path a is used to image the eye ^! About Ophthalmitkoplinse A main objective 5, intermediate objective 7, tilting mirror 8, folding prism 11, bilddrehsnd «; unit 27 and tube lens in the

Okuiarbildebene 29. About the beam path a, the fundus may be becheck by the examiner ¹ ). If the folding mirror 8 is unfolded and replaced by a 90 ° offset semitransparent mirror and the folding prism 11 is swung out of the beam path, you can be photographically or otherwise registered via a beam path f in the normal fundus image you exact location.

The image of a mark 25, which is in congruent position to a CCD line 26, is recorded via folding mirror 24 during the observation via beam paths a _m1 , a _m j, a _m and Klanpprisma 11 in the Okuiarbildebene 29. The tag 25 may be photographically registered as the prism 11 is pivoted, as described above.

The beam path a _m consists of a first lens 12, a first image-rotating.; Unit 13, a field lens 15, aperture 16 and e'nem first beam splitter 17th

The beam paths a _m t, a _m2 contain objective »18,18 ', wherein 18' is arranged vorschiebbar in the direction of the optical axis.

In a _m i, the objective 18 is followed by a second image-rotating unit 19. Swiveling filters 20, 20 'are provided in both beam paths.

By means of a beam splitter unit 21 a, b both Strahlengä.ige be merged and imaged via an objective 22 in the plane of the CCD line 26.

Via intermediate objective 7 and objective 12, the second intermediate image 6 generated from the arsenal intermediate image 3 via the main objective 5 is imaged into the intermediate image plane 14. About the lenses 18,18 'and 22, the image of the intermediate image 14 takes place in the receiver plane.

Via the image rotating unit 12, the fundus image imaged on the CCD line 26 can be optically rotated.

The beam splitter 21 a, b consists of a tiltable about two axes part 21 a and a fixed part 21 b. By a defined, fixed tilting of 21 a is achieved that the superimposed itself sub-images m ,, m _{2 of} the beam paths a _ml , 9m2 offset from each other in the row level 26 are shown, so that both fields are next to each other and by a narrow separation zone from each other are separated.

In this case, the CCD line 26 is in the field of fields, wherein the same measurement locations of the fields different areas of the CCD line are assigned.

Upon further tilting of 21 a around the fixed base tilt, the measuring locations are shifted in both partial images, depending on the tilting axis in the row direction or perpendicular thereto (see Fig. 2).

Through the image rotating unit 13 both Teil'jilder can be rotated evenly against the line position. By means of the image-rotating unit 19, one of the partial images can additionally be rotated against the other, so that z. B. the Menagen shown in Fig. 3 can be realized.

Due to the swing-out filter 20,20 'different characteristics can be achieved in both fields.

By displacement of the lens 18 ', the partial image m ₂ is displaced in the direction of the optical axis and therefore shown opposite to, defocused.

A similar effect can be obtained if the apertures of a _m1 and a _{m2 are made} different. It is possible to replace the objective 22 by a system of crossed cylindrical lenses 23 of different refractive power.

In this case, the sub-images m _t and m _{2 are} imaged in one axis in a magnification relative to the other axis. The same change is also effective on the incorporated in the eyepiece brand arrangement.

Due to the changed magnification, d. H. the "crowding" of the image is achieved so that the sensitivity of the system increases by increasing the light intensity on the receiver surface.

By replacing the beam splitter 17 (ng.4) with a beam splitter 10 (FIG. 5), the sub-images mi, m _; u Stereo fields that do not have to be congruent or have the same spectral characteristic.

The manipulations described in a. ",, a _m1 , a _m2 have the same effect on the line mark image 25 and be ne imaging in the eyepiece 29 from (when the hinged prism 11, ie in the observation phase).

Instead of a line 26, which at least partially covers both sub-images, a separate line can be used for each .silbild or find a CCD matrix or other recording system use.

The CCD line 26 is connected to a control and evaluation computer 30, via which the control of all adjustable elements takes place.

Claims (18)

1. Arrangement for measuring on the background of the patient, wherein a picture of the fundus is made on a CCD line and a Boleuchturigsstrahlengang is provided for at least strobe lighting of the fundus, characterized in that one and the same field of view of the fundus is imaged on at least two CCD line segments, wherein means for changing the image position and the optical properties of the image are provided. 2. Arrangement according to claim 1, characterized in that the line sections are components of one and the same CCD line. 3. Arrangement according to claim 1, characterized in that the line sections are components of several CCD lines. 4. Arrangement according to claim 1, characterized in that the line sections are each CCD lines. 5. Arrangement according to one of claims 1-4, characterized in that the imaging beam path is partially split. 6. Arrangement according to claim 5, characterized in that a picture-rotating unit is provided in the non-split part of the imaging beam path. 7. Arrangement according to claim 5 or 6, characterized in that at least in one of the split parts of the imaging beam path, a picture rotating unit is provided. 8. Arrangement according to claim 7, characterized in that spectral filters are provided. 9. Arrangement according to claim 7, characterized in that polarization filters are provided. 10. Arrangement according to claim 7, characterized in that a displaceable in the direction of the optical axis lens is provided. 11. Arrangement according to claim 7, characterized in that a beam direction changing, tiltable about two axes prism is provided. 12. Arrangement according to one of claims 1-11. characterized in that on the Beleuchtungsstrp.hlengang a continuous lighting is realized. 13. Arrangement according to one of claims 1-11, characterized in that the suppression of an observation beam path from the imaging beam path takes place. 14. Arrangement according to claim 13, characterized in that the suppression takes place via a pivotable deflection unit. 15. Arrangement according to claim 14, characterized in that via a prism having a plurality of reflective surfaces, the imaging beam path and a CCD row congruent brand arrangement are superimposed in the observation beam path. 16. Arrangement according to one of claims 1-15, characterized in that a pivotable folding mirror is provided in the imaging beam path, which is replaced for the purpose of image recording by a partially transparent, rotated by 90 ° relative to the folding mirror mirror. 17. Arrangement according to claim 5, characterized in that the splitting as amplitude division provided for beam splitter erse.zt by a stereo beam splitter for wavefront division. 18. Arrangement according to one of claims 1-17, characterized in that an arrangement of crossed cylindrical lenses is provided in the imaging beam path in the vicinity of the CT.D receiver.