METHOD FOR CLASSIFYING THE CATARACT OF AN EYE

Abstract

A method for classifying a cataract of an eye to determine parameters for pre-setting phaco-treatment instruments. OCT-based measurements are realized. The OCT-based scans are analysed using imaging technology and the local distribution of the cataract is determined. The cataract is classified on the basis of comparison values and the local distribution and classification of the cataract are used to identify parameters for pre-setting phaco-treatment instruments. Even though the proposed method for classifying the cataract of an eye is provided for determining parameters for pre-setting phaco-treatment instruments, it should equally also be used for determining parameters for pre-setting treatment instruments based on fs-lasers.

Claims

1.-20. (canceled)

21. A method for classifying a cataract of an eye for determining parameters for presetting phaco-treatment instruments, comprising: acquiring OCT-based measurements; analyzing the OCT-based scans using imaging technology; determining a local distribution of the cataract; classifying the cataract based on comparison values; and determining the parameters for the pre-setting of phaco-treatment instruments from the local distribution and the classification of the cataract.

22. The method according to claim 21, further comprising: determining required biometric data for a phaco-treatment from the OCT-based measurements; determining the parameters for pre-setting the phaco-treatment instruments from the biometric data, the local distribution and the classification of the cataract.

23. The method according to claim 21, further comprising: along with the OCT-based measurements, acquiring keratometric measurements; determining biometric data for a phaco-treatment from the keratometric measurements and OCT-based measurements; determining parameters for the pre-setting of phaco-treatment instruments from the biometric data, the local distribution and the classification of the cataract.

24. The method according to claim 21, further comprising acquiring the keratometric measurements at at least one point.

27. The method according to claim 24, further comprising acquiring the keratometric measurements at at least six points.

26. The method according to claim 24, further comprising acquiring the carrier metric measurements at at least eighteen points.

27. The method according to claim 21, further comprising acquiring the OCT-based measurements based on a swept source laser light source.

28. The method according to claim 27, further comprising utilizing the swept source laser light source such that the swept source laser light source emits short coherent light with a wavelength between 800 nm and 1100 nm.

29. The method according to claim 27, further comprising utilizing the swept source laser light source such that the swept source laser light source emits short coherent light with a wavelength of 1060 nm.

30. The method according to claim 27, further comprising utilizing the swept source laser light source such that the swept source laser light source has a spectral bandwidth between 3 nm and 260 nm

31. The method according to claim 27, further comprising utilizing the swept source laser light source such that the swept source laser light source has a spectral bandwidth between 10 nm and 100 nm.

32. The method according to claim 27, further comprising utilizing the swept source laser light source such that the swept source laser light source has a spectral bandwidth between 20 nm and 40 nm.

33. The method according to claim 21, further comprising determining required biometric data for a phaco-treatment from the OCT-based measurements with an axial resolution <27 m and the lateral resolution <100 m.

34. The method according to claim 21, further comprising acquiring the OCT-based measurements in the form of B scans along the optical axis, wherein depth of the B scans corresponds to a total length of the eye and width of the B scans corresponds to an entire pupil of the eye.

35. The method according to claim 27, further comprising making the OCT-based measurements performing B scans along at least 2 different meridians.

36. The method according to claim 27, further comprising making the OCT-based measurements performing B scans along at least 6 different meridians.

37. The method according to claim 27, further comprising making the OCT-based measurements performing B scans along more than 10 different meridians.

38. The method according to claim 26, further comprising in the case of the OCT-based measurements detecting only those radiation components reflected from a boundary surface that enclose an angle of a maximum of 10 with the visual axis of the eye.

39. The method according to claim 21, further comprising analyzing the OCT-based scans using imaging technology by assessing the brightness of individual structures.

40. The method according to claim 21, further comprising utilizing a brightness distribution thus determined of a structure of an eye lens for a purpose of classifying the cataract on a basis of comparison values.

41. The method according to claim 21, further comprising determining the classification of the cataract in the following three steps: soft cataract medium cataract hard cataract

42. The method according to claim 40, further comprising determining the classification of the cataract in more than three steps.

43. The method according to claim 21, further comprising acquiring the OCT-based measurements; further analyzing the OCT-based scans using imaging technology; further determining the local distribution of the cataract; further classifying, the cataract based on comparison values; and further determining parameters for the pre-setting of phaco ultrasound-treatment instruments or laser phaco-treatment instruments from the local distribution and the classification of the cataract.

44. The method according to claim 21, further comprising determining the parameters for the phacoemulsification additionally dependent on treatment method, a phaco needle used and on a technique of an attending physician.

45. The method according to claim 21, further comprising determining performance parameters of a femtosecond laser defined as parameters for laser-phaco, including at least one of pulse energy, repetition rate, point spacing, type of radiation pattern and number of sectional planes.

46. The method according to claim 45, further comprising selecting the parameters for pre-setting the laser-phaco such that the femtosecond laser system is used to support a subsequent phacoemulsification.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In the following the invention will be described in greater detail based on exemplary embodiments. The figures show the following:

[0035] FIG. 1: shows a pupil with 18 keratometric measurement points,

[0036] FIG. 2: shows an OCT scan of the entire eye,

[0037] FIG. 3 shows six meridians for OCT scans to be performed and

[0038] FIG. 4 shows segments of OCT scans to be analyzed performed under different meridians.

DETAILED DESCRIPTION

[0039] In the case of the inventive method for classifying a cataract of an eye for determining parameters for pre-setting of phaco-treatment machines, OCT-based measurements are realized, the OCT-based scans are analyzed using imaging technology and the local distribution of the cataract is determined, the cataract is classified on the basis of comparison values and parameters for pre-setting phaco-treatment machines are determined from the local distribution and the classification of the cataract.

[0040] In accordance with the invention, in the case of the method the required biometric data for a phaco-treatment can be determined from the OCT-based measurements and parameters for pre-setting phaco-treatment machines can be used for classification of the cataract.

[0041] However, it is also possible to realize keratometric measurements along with OCT-based measurements, determine the biometric data required for a phaco-treatment from the OCT-based and the keratometric measurements and determine parameters for the pre-setting of phaco-treatment machines from the biometric data, the local distribution and the classification of the cataract.

[0042] According to a first embodiment, keratometric measurements take place in at least one, for example 6 and in another example 18 or more measurements.

[0043] With the keratometric measurement the surface curvature of the cornea of the eye as well as the corneal curves are determined. In the process, an illuminated object is set up at a known distance and the reflection of the cornea is measured in order to be able to draw conclusions about the curvature of the cornea. The precision of the determination of the surface curvature of the cornea rises logically with the number of measuring points.

[0044] To this end FIG. 1 shows an eye pupil AP with 18 keratometric measuring points P.sub.K1 to P.sub.K18.

[0045] According to a second embodiment, a swept source laser light source is used for the OCT-based measurements which emits short-coherent light with a wavelength between 800 nm and 1100 nm, for example 1060 nm. The OCT-based measurements have an axial resolution <25 m and a lateral resolution <100 m.

[0046] The optical coherence tomography is a very sensitive and rapid method for interferometric imaging, which has found widespread application in particular in the medical field and in basic research.

[0047] The swept source laser light source is a spectrally tunable light source. The OCT-based measurements are hence based on a frequency domain OCT. In the process, to achieve a suitable measuring depth in the eye and a necessary depth resolution, an axial OCT scan depth of 2 mm to 2 m, in particular 60 mm in the air as well as a spectral bandwidth of the radiation source between 3 nm and 260 nm, preferably between 10 nm and 100 nm and especially preferably between 20 nm and 40 nm are provided. Thus, in the case of a sufficient scan depth over the entire eye and in particular the lens a depth resolution of 25 m in the lens tissue can be achieved, with which the substructure of the lens can be sufficiently characterized. In order to also achieve an appropriate lateral resolution of the scattering particles in the cataract lens, provision is made to design the aperture, focusing and lateral scan resolution such that the lateral resolution of the OCT biometer 100 m. In accordance with the invention, that is necessary in order, in particular in addition to the good local allocation of the scattering intensities, to be able to carry out a sufficient assessment of the scattering structures. A further embodiment of a frequency domain OCT method can occur with a wide-band light source, such as e.g. a super luminescence diode (SLD), in which case the information is obtained by means of a spectrometer.

[0048] One great advantage of the OCT is the decoupling of the depth resolution from the transverse resolution. As a result, very good axial resolutions can be achieved, also in the case of limited numeric apertures. The OCT measurements based on backscattered radiation and reflection hence facilitate the generation of microscopic images of living tissue (in vivo).

[0049] One advantage of the swept source laser light source used here can be seen in the fact that the entire eye length can be recorded in only one A scan. Moreover, with the swept source-based technology, in particular in the B scan differing lateral local scattering properties of the eye lens can be resolved, which result from different cataract degrees and with which different optical and thus also mechanical properties correlate.

[0050] Thus it is possible to detect existing differences in the cataract degrees in the core and cortex of the eye lens and specify them as local distribution of the cataract. From this local distribution an average parameter can then be determined for classification of the cataract.

[0051] In order to detect the biometric data contained within from the OCT-based measurements, for example the eye length known image analysis methods are employed. To this end FIG. 2 shows an OCT scan of the entire eye, in which the cornea H, the eye lens AL and the retina R can be clearly recognized.

[0052] The selection of the mentioned wavelengths occurs against the background that the tissue of the human eye shows the highest transmission in the case of longer wavelengths in the near-infrared spectral range and as a result permits even the detection of the comparatively low scattering efficiency and even slight differences can be detected in the scattering behavior with high resolution. In the process, the high sensitivity of the swept source-based OCT method, approximately, 80-100 dB is very helpful. In contrast to the inventive arrangement, Scheimpflug methods use the high scattering coefficients of short-wave visible light with a high color temperature. With this, in particular in the case of denser cataracts often an overexposure can be observed in the scattering image, as a result of which the resolution suffers.

[0053] According to a third embodiment the OCT-based measurements take place in the form of B-scans along the optical axis, wherein their depth corresponds to the entire length and their width corresponds to the entire pupil of the eye. In the process, at least 2, preferably 6 and especially preferably more than 10 B scans are realized along different meridians.

[0054] To this end FIG. 3 shows an eye pupil AP with six meridians M.sub.S1 through M.sub.S6 for OCT scans to be performed. Although the meridians MS for OCT scans to be performed are evenly distributed in FIG. 3, this is not absolutely necessary. On the contrary, it is also possible to place the meridians more narrowly in the interesting regions depending on the detected cataract distributions or to carry out OCT scans in further meridians.

[0055] It goes without saying that the classification of a cataract of an eye and thus also the determination of parameters for pre-setting phaco-treatment machines become more precise, the more OCT-based measurements are realized. In particular, in this regard it is also possible to resort to a new optical tomographic method, holoscopy. Holoscopy combines the advantages of OCT and holography in medical imaging.

[0056] While optical coherence tomography (OCT) has been established for many years in medical technology, holoscopy has just been introduced. The method for 3D imaging a scattering sample, in particular for determining the spatial scattering intensity distribution S(x, y, z) of the sample is described in DE 10 2011 018 603 B3.

[0057] The short-coherent light of the swept source laser light source is directed along the optical axis into the human eye and scanned in transverse direction over the full eye pupil of about 6 mm.

[0058] In accordance with the invention, in this connection only the radiation of the swept source laser light source is detected which is scattered directly back from the boundary surfaces and from the lens volume. Radiation that is scattered directly back means the radiation which includes an angle of a maximum 10.

[0059] This angular region of <+/10 correlates well with the actual anatomical symmetry of the human eye. As a rule, the optical axis of the human eye is inclined about 5 to the side of the nose.

[0060] According to a further embodiment, the OCT-based scans are analyzed using imaging technology by assessing the brightness of the individual structures.

[0061] The realized OCT scans show all structures of the relevant eye, wherein each individual structure shows different reflection and scattering degrees due to specific refractive indexes and tissue densities.

[0062] In this method, in accordance with the invention the individual segments of the OCT-based scan are given priority in the analysis with respect to the distribution of the brightness, said segments correlating directly with the local tissue density. Further, provision is made to support the diagnostic statements about the degree of hardness of the lens through additional image processing, in which along with the brightness also the inner structural features of the scattering lens (Architecture of the Cataract) are classified and as a result, or together with the scatter intensity an estimate of the expected degree of hardness takes place.

[0063] To this end FIG. 4 shows the segments to be analyzed of the OCT scan conducted under different meridians. The analysis of the individual segments shows in particular the following results from left to right: [0064] The air L in the case of a refractive index of n=1.0 shows no scattering/reflection. [0065] As an optical element of the eye with a defined tissue density and a higher refractive index of n=1.38 the cornea H shows a significant scattering/reflection. [0066] The aqueous solution WL through its liquid state and a lower refractive index of n=1.34 shows a significantly lower scattering/reflection than the cornea. [0067] The eye lens AL shows significant brightness curves that arise from the cataract degree and the opacity of the lens. The OCT-based scans of the lens along 6 evenly distributed meridians M.sub.S1 through M.sub.S6 are presented here. As a rule the lens has refractive indexes of from n=1.39 to n=1.41 and has differing tissue densities.

[0068] The different cataract types are assigned to different groups in dependency on their brightness values and/or structural features, said groups for which corresponding parameters are defined for pre-setting the phaco-treatment machines.

[0069] In accordance with the invention, the brightness distributions thus determined and/or the structure of the eye lens serve the purpose of classifying the cataract on the basis of comparison values. For example, this can take place in the following 3 steps:

[0070] a) soft cataract,

[0071] b) medium cataract and

[0072] c) hard cataract.

[0073] This corresponds to the following parameters for the pre-settings:

[0074] a) soft cataractlow parameters for phacoemulsification

[0075] b) medium cataractmedium parameters for phacoemulsification

[0076] c) hard cataracthigh parameters for phacoemulsification

[0077] However, the classification is not limited to the steps mentioned above, but rather could also take place in more than 3 steps.

[0078] According to a further embodiment, parameters for the pre-setting of phaco-treatment machines are determined from the biometric data, the local distribution and the classification of the cataract, wherein the parameters for the pre-setting of phaco-treatment machines vary correspondingly depending on the device to be used for the phaco-treatment or the technology to be applied (e.g. divide and conquer or chip).

[0079] To this end, OCT-based measurements are realized, the OCT-based scans are analyzed using imaging technology and the local distribution of the cataract is determined, the cataract is classified on the basis of comparison values and the parameters for the pre-setting of the phaco-treatment machines are determined from the local distribution and the classification of the cataract.

[0080] The parameters for the (ultrasound) phacoemulsification are in the process additionally dependent on the treatment method, the phaco-needle used (20 g/21 g/22 g) and even the technique of the attending physician.

[0081] In the case of the phacoemulsification, the eye lens is fragmented by use of a tube or needle induced by ultrasound and the debris subsequently suctioned by use of a suction rinsing device. In addition to the ultrasound energy, the most important parameters have to do with the control of the rinsing and suction pressure.

[0082] According to a further embodiment, OCT-based measurements are realized, the OCT-based scans are analyzed using imaging technology and the local distribution is determined, the cataract is classified on the basis of comparison values and parameters for the pre-setting of laser phaco-treatment devices are determined from the local distribution and classification of the cataract.

[0083] Essentially the performance parameters of the fs laser are defined as parameters for the laser-phaco, such as pulse energy, repetition rate, point spacing or type of radiation pattern and number of sectional planes.

[0084] Along with the ultrasound-based phacoemulsification, the laser-phaco method based on fs lasers is becoming increasingly important and is in widespread use in cataract surgery due to the safe cutting and an improved lens fragmentation

[0085] The performance parameters of the surgical fs laser, such as pulse energy and repetition rate, are required especially for lens fragmentation, in order to be able to effectively and securely fragment the lens tissue corresponding to its optical scattering properties and the associated cataract degree.

[0086] In accordance with the invention, the OCT-based data of a prior diagnosis can be used to set the parameters for an fs laser system. If the surgical fs laser system has an integrated OCT imaging or navigation system, in addition the diagnostics can occur or can also be repeated shortly before the OP, i.e. in the operating room.

[0087] According to a further embodiment, the parameters for pre-setting the laser-phaco can be selected such that the fs laser system is used for support of the subsequent phacoemulsification.

[0088] Hence it would be possible to generate a complete workflow also for fs laser supported cataract operations and perform the fragmentation of the eye lens with the help of the fs laser in order to finally generate the correct settings for the phasoemulsification from the OCT-based biometry data prior to the operation. For this purpose, in particular the postoperative diagnostic data of the OCT imaging or navigation system integrated in the fs laser can be used to predict the setting of the phaco-treatment machine.

[0089] A special adjustment of the final settings for the phasoemulsification in the fs laser-supported cataract operation can take place by using OCT-based data of the lens after fragmentation by application of fs laser.

[0090] The inventive solution provides a method for the classification of the cataract of an eye for determining parameters for pre-setting phaco-treatment machines with which, along with keratometric measurements, in addition OCT-based measurements can be realized, the required biometric data for a phaco-treatment determined from the kerametric and OCT-based measurements, the OCT-based scan can be analyzed using imaging technology and the local distribution of the cataract determined, the cataract can be classified on the basis of comparison values and the parameters for the pre-setting of phaco-treatment machines can be determined from the biometric data, the local distribution and the classification of the cataract.

[0091] With the proposed method for classifying the cataract of an eye a simple and reliable classification and the generation of parameters for pre-setting phaco-treatment machines is possible, wherein the geometry of the respective eye is considered. Manual or automatic setting of the phaco-treatment machines makes the treatment safer and reduces the burden on the patient.

[0092] One advantage of the method can be seen in the fact that it is suitable both for the classification of the cataract of an eye for generating parameters for pre-setting of ultrasound-based as well as laser-based phaco-treatment machines.

[0093] The proposed method provides for the consideration of both the biometric data, in particular of the eye length, as well as the classified cataract data.

[0094] In the case of laser-based phaco-treatment machines, the advantage for the patient can be seen in the fact that the laser parameters (pulse energy, repletion rate, point spacing) as well as the number of sectional planes, patterns as well as pattern density are determined such that the operation can be carried out with the lowest possible laser power or light dosage.