DEVICE FOR MEASURING BIOMETRIC QUANTITIES OF THE EYE

Description

[0001] The present invention relates to a device for measuring biometric parameters of the eye, which are particularly useful in the calculation of intraocular lenses.

[0002] Such parameters include the radii of the anterior and posterior surfaces of the cornea, along with their asphericity and thickness; the radii of the anterior and posterior surfaces of the lens, along with their thickness; and the anterior chamber depth and axial length of the eye. Also relevant are the position and shape of the optically effective interfaces, or surfaces optically relevant for the eye's vision, such as the anterior and posterior surfaces of the cornea, the anterior and posterior surfaces of the lens, and the retina. These parameters, or some of them, are required for the calculation of intraocular lenses—hereinafter referred to as IOL calculation—using established IOL formulas or ray-tracing methods.

[0003] Currently, only OCT (optical coherence tomography) systems and topography / OCT combination systems are known for measuring the biometric parameters of the entire eye. While Scheimpflug, PCI (partial coherence interference), topography systems, or combination devices of these, measure some of the aforementioned parameters, these combinations cannot measure all parameters of the eye.

[0004] In particular, it is not possible to measure the back of the lens and the retina or the respective profile of these surfaces, since these systems, even in a combined system, are limited to measuring the anterior chamber and the axial one-dimensional length of the eye.

[0005] WO 2019 / 076335 discloses an OCT arrangement with a measurement mode for the anterior segment of the eye and a measurement mode for the posterior segment of the eye (paragraphs 64-65). An optical element (14-16, Figure 9) is positioned in front of the xy-scanner to switch between the modes (paragraph 107). When switching between the measurement modes, the xy-scanner is illuminated convergently or with collimated light (Figures 9-10).

[0006] Only OCT systems that measure the anterior and posterior chambers of the eye, and topography / OCT systems that also measure the anterior and posterior chambers, are capable of measuring the entire eye.

[0007] Another possible combination is topography / Scheimpflug imaging for measuring the anterior chamber and OCT for the posterior chamber. However, since OCT can also assess the anterior chamber, the benefit of Scheimpflug anterior chamber measurement is minimal compared to the additional costs.

[0008] Compared to combined topography / OCT systems, pure OCT systems have the disadvantage that measuring corneal topography using classic topometers (especially Placido systems) is significantly more accurate than the measurements of OCT systems, which are affected by motion artifacts. While these motion artifacts can be reduced by faster measurements or by precisely recording the eye's position, this is only possible with considerable effort and is not always reliably sufficient.

[0009] A topography / OCT combination system, such as the one described in US 2004 / 066489 A1, combines a Placido topographer with a time-domain B-scan OCT. In principle, this allows for biometric measurement of the entire eye. However, the described device exhibits several significant drawbacks that reduce the reliability of the measurements. While Placido topography offers very high resolution, its surface reconstruction is less reproducible compared to keratometer measurements. This is due, firstly, to the assumptions used in topography reconstruction to achieve the high resolution, and / or, secondly, to the lack of telecentricity / insufficient focusability of many topography systems compared to keratometers. As a result, positioning errors of the measuring device relative to the patient become relevant during topography measurement and reduce the accuracy of the measurement.

[0010] Since this solution illuminates the scanner and eye identically in both measurement modes, and there are no means to change the divergence of the light hitting the eye depending on the region of the eye being examined, neither the retina nor the cornea measurement mode produces a sharply defined focus, and the spatial resolution is very low.

[0011] Furthermore, Placido topographers do not allow for the consideration of so-called skerf rays, which always occur when illuminating Placido rings if the cornea is curved not only in a median plane through the corneal vertex but also in a plane perpendicular to it, i.e., azimuthally. This omission results in an inaccurate representation of the corneal surface. Therefore, a Placido topographer does not reliably represent the radius or, more generally, the anterior surface of the cornea as required for IOL calculations.

[0012] Furthermore, time-domain OCT systems are too slow, and price-acceptable spectrometer-based systems either lack the necessary axial resolution and / or have insufficient axial scan or acquisition depth, meaning that the axial length measurement is not performed with the resolution required for IOL calculation, or is performed in such a way that only partial depth measurements are obtained. Whole-eye biometry, i.e., determining the optically relevant surfaces of the entire eye in terms of their position and profile, is theoretically possible in both cases by separately measuring the anterior and posterior chambers and subsequently synthesizing the data, but it is unreliable and / or inaccurate.

[0013] Therefore, the Placido Time Domain OCT system does not allow for a sufficiently reliable and simple acquisition of all biometric data for IOL calculation.

[0014] US patent 2005 / 0203422 A1 describes a topography / OCT combination system consisting of a simple keratometer and a B-scan OCT. This system also allows for the determination of important biometric parameters of the eye. However, the described device also exhibits some significant disadvantages that reduce the reliability of the measurements or leave open important aspects relevant to comprehensive eye biometry.

[0015] The described keratometer only allows for the robust measurement of the radii of the anterior cornea. A description of the corneal surface with a higher order or resolution than that of the described keratometer is not possible. However, this is increasingly required for the calculation of intraocular lenses (IOLs), especially toric IOLs.

[0016] Furthermore, neither the problem of assigning the topography measured by keratometer to the location data of the OCT data is solved, nor is it ensured that the OCT measurements are performed particularly quickly in order to compensate for eye movement during the measurement.

[0017] A device for the reliable determination of biometric measurements of the entire eye is described in DE 10 2012 019474 A1. The device is based on a multipoint keratometer and an OCT array, wherein the multipoint keratometer is designed such that the keratometer measurement points are collimated, illuminated, and detected telecentrically. The OCT array is designed as a laterally scanning sweptsource system with a detection range encompassing the entire axial length of the eye.

[0018] A disadvantage of this solution is that the scanner deflection in anterior chamber mode is smaller than in retinal mode, due to the distance between the scanner and the eye and the absence of lenses between the scanner and the eye. To ensure high angular resolution with large rotation angle ranges in both modes, sophisticated control systems and extremely precise scanner construction are required. If the distance between the scanner(s) and the eye needs to be increased further due to other illumination units or measurement functions within the device, such as an illumination unit for a keratometer with hundreds of points, the angular resolution requirement becomes even more stringent, to the point where commercially available scanners can no longer meet these requirements.

[0019] A further disadvantage is that in retina mode, only one of the scanners is at the correct distance from the ocular lens to align the beam's pivot point with the pupil. Therefore, only a 1-dimensional retina scan is possible. While 2-dimensional scans can be achieved in anterior chamber mode, the beam deflection can only be divergent. This means that the angle between the optical axis and the beam increases with the scanner's deflection because the optics between the scanner and the eye are swung outwards.

[0020] The combination of the OCT system with the device's other measurement functions necessitates a minimum distance between the scanners and lenses and the eye, resulting in a relatively large beam diameter on the scanner mirrors. Larger mirrors are inherently slower to move than smaller ones, thus hindering short measurement times, which are always desirable due to potential eye movements.

[0021] Switching between retina and anterior chamber modes is achieved by laterally pivoting the optics in front of and behind the scanners. However, increasing the scan angle requires considerable installation space, particularly for pivoting the optics after the scanner. Furthermore, the tolerances necessitate highly precise mechanical stops to achieve the required image quality and a stable image center during the switching process.

[0022] Another system, consisting of a microscope and an OCT system, is described in DE 10 2015 012 387 A1. This system also provides measurement modes for the retina and the anterior chamber, with switching between them achieved by swiveling lens systems into position.

[0023] The large number of components required for the switching mechanism has a negative impact. Furthermore, the distance between the optical system and the eye differs significantly in the two measurement modes, which greatly complicates handling in practice.

[0024] The present invention aims to disclose a device that provides fast, reliable, reproducible, and accurate measurements of biometric parameters of the eye relevant for the calculation of intraocular lenses, with the necessary accuracy and resolution. The measurement should preferably be based on whole-eye scans that can determine the position and profile of the optically relevant surfaces of the entire eye. The device should offer the possibility of two different measurement modes for the anterior (anterior chamber) and posterior (retina) segments of the eye, requiring as few components and as little installation space as possible for switching between modes. Furthermore, the position of the eye should remain constant, and the scanner should be usable with similar deflections in both modes.

[0025] This problem is solved by the device according to claim 1 for measuring biometric parameters of the eye for calculating intraocular lenses, comprising a multipoint keratometer and an OCT arrangement designed as a scanning sweptsource system with a measuring range encompassing the entire eye and having two measuring modes, in that the scanner of the OCT sweptsource system is a 2D scanner, that an axially displaceable optical element is arranged in the beam path between the 2D scanner and the eye to be measured for varying the measuring modes, and that optical elements are present in the beam path between the 2D scanner and the interferometer of the OCT sweptsource system, which, depending on the measuring mode to be set, are either selectively located in the beam path or are axially displaceable. In particular, two optical elements can be present, which are selectively located in the beam path.

[0026] According to the invention, the problem is solved by the features of the independent claims. Preferred embodiments and configurations are the subject of the dependent claims.

[0027] The multipoint keratometer ensures that, firstly, a sufficient number of keratometer points are available for high-resolution measurement of the corneal surface. Secondly, telecentricity ensures that positioning deficiencies of the measuring device relative to the eye being measured do not lead to a mislocation of the reflection points.

[0028] The Sweptsource OCT scan, which captures the entire length of the eye, makes it possible to detect both anterior chamber and retinal structures in the A and B scans, respectively, thus enabling orientation based on the retina and cornea (anterior chamber).

[0029] Although the proposed device is preferably based on a swept-source OCT system, time-domain, frequency-domain, or spectral-domain OCT systems are also applicable. However, swept-source OCT ensures faster measurement of A-scans across the entire eye length than other OCT variants, and is also free of motion artifacts.

[0030] The invention is described in more detail below with reference to exemplary embodiments. These include: Figure 1: the schematic representation of the device according to the invention, Figure 2: a preferred embodiment of the device according to the invention in retina mode and Figure 3: a preferred embodiment of the device according to the invention in anterior chamber mode.

[0031] The proposed device for scanning measurement of the eye consists of an OCT arrangement with a measurement mode for the anterior segment and a measurement mode for the posterior segment of the eye.

[0032] According to the invention, an optical element is arranged between the xy-scanner and the eye, which is axially displaceable for switching between the modes, and the xy-scanner is illuminated convergently or divergently for switching between the modes.

[0033] In this process, the xy scanner is focused and illuminated in retina measurement mode, and the optical element projects the scanner's pivot point into the pupil of the eye, while in anterior chamber measurement mode the optical element is shifted towards the xy scanner and the scanner is illuminated divergently.

[0034] According to a first embodiment, the proposed device for measuring biometric parameters of the eye for calculating intraocular lenses consists of a multipoint keratometer and an OCT arrangement designed as a scanning sweptsource system with a measurement range covering the entire eye and having two measurement modes.

[0035] According to the invention, the scanner of the OCT sweptsource system for deflecting the OCT beam perpendicular to the optical axis is designed as a 2D scanner, which can consist of two scanners for x and y deflection with or without intermediate imaging. Preferably, it is a two-axis scanner (xy scanner) or MEMS.

[0036] In contrast to the state of the art, the scanner is illuminated with a focused beam, with the focus of the illumination light being in front of or behind the scanner or scanners.

[0037] Furthermore, according to the invention, an axially displaceable optical element is arranged in the beam path between the 2D scanner and the eye to be measured to vary the measurement modes. Additionally, a delay line and at least one variable optical element are provided in the beam path between the 2D scanner and the interferometer of the OCT sweptsource system. This variable optical element shifts the focus of the light incident on the scanner in front of or behind the scanner to vary the measurement modes. This variable optical element can also be an axially displaceable lens or lens combination, or consist of two elements that are selectively positioned in the beam path depending on the measurement mode to be set.

[0038] Both the movable and the optionally insertable optical elements are designed as lenses or lens systems. These lenses or lens systems are preferably dimensioned such that their distances and focal lengths are in a fixed ratio to each other.

[0039] This shows the Figure 1 A schematic representation of the device according to the invention based on a multipoint keratometer 1, OCT setup 2 and a (not shown) sweptsource system. The multipoint keratometer 1 is via the one on the device axis 3 arranged beam splitter 4 with the beam path of the OCT arrangement 2 combined. The OCT arrangement features a variable measurement mode. 2 in the beam path between the scanner 6 and the eye to be measured 5 a movable lens 7 and in the beam path between the scanner 6and the interferometer 8 A prism as a delay line 9 and a deflecting angle mirror 10, as well as two lenses as a variable optical element 11 and 12, which are located in the beam path depending on the measurement mode to be set.

[0040] According to the invention, the lens is used for the retina measurement mode. 7 in the path of the light rays towards the eye 5, moved to a position farther from the scanner. Additionally, the lens is located 12 in the beam path.

[0041] This shows the Figure 2 A preferred embodiment of the device according to the invention in retina mode. Here, the distance of the lens corresponds to 7 to the scanner 6 and to the eye 5 Each with twice its focal length. In this particularly simple form, it is therefore an image of the scanner. 6The beam deflection at the scanner is measured in the eye pupil with a scale of M=1. 6 is converted 1:1 into the deflection at the eye 5 Translated. Translations that differ from this are indicated by differing distances between scanners. 6, lens 7 and eye 5 reachable.

[0042] In retina measurement mode, the lens 7 so that it is used for pupil imaging, whereby scanners 6 with a scale M1 into the pupil of the eye 5 is imaged. At the same time, the lens causes 7, that the light, which with its focus on a circular path around the scanner 6 moved, collimated onto the eye 5 hits, and at the back of the eye 15 The lens is focused. 7 This thus forms from around the scanner 6 centered intermediate image 17 into the image plane at the back of the eye 15 away.

[0043] Furthermore, the circular path on which the intermediate focus (the curved intermediate image) is located lies 17 ) moved during scanning, in retina measurement mode between scanners 6 and lens 7. Intermediate frame 17 and lens 7 are therefore in comparison to Figure 3 to the eye 5 shifted. The focus of the incoming light passing through the lens 12 The point of focus lies at the distance of the focal length F of the lens. 7 behind the scanner 6. The movement of the scanner 6 This illuminates an intermediate image with radius r = F and lies concentrically around the scanner. 6. The magnification of the lens 7 from scanner to eye 5 In this simplest configuration, M = 1.

[0044] According to a preferred configuration, for example, the following parameters can be used in retina measurement mode to create a pupil image from the scanner to the eye: Focal length of the lens 7 of F=30mm, distance of the lens 7 from the eye 5 and from the scanner 6 of 2F=60mm, a scanner mirror rotatable by + / -5 degrees with a diameter of approximately 3mm and a focal length of the lens 12 of F=120, at a distance from the scanner 6 of 90mm.

[0045] With this design, a beam with a diameter of 2mm can be moved at the eye within an angular range of + / -10 degrees.

[0046] According to the invention, the lens is used to switch from retinal measurement mode to anterior chamber measurement mode. 7 towards scanner 6, moved to a position closer to the scanner. Additionally, the prism serving as a delay line is located there. 9 and the deflecting angle mirror 10, as well as the lens 11 in the beam path.

[0047] This shows the Figure 3A particularly simple and preferred embodiment of the device according to the invention in the front chamber measuring mode. Here, the distance of the lens corresponds to 7 to the scanner 6 their focal length and the distance to the eye 5 whose focal length is three times greater.

[0048] The scanner 6 and the focal plane of the lens 7 This coincides, so that a telecentric OCT beam is directed at the eye. 5 This is generated, which shifts parallel to the optical axis during the scanning process. Furthermore, the lens... 11 arranged so that the focus 16 of the incident light half a focal length in front of the scanner 6 lies. This is how the lens creates 7 not only a telecentric scanning beam, but simultaneously a focus at the location of the eye 5, at a distance of 3 times the focal length of the lens 7 lies.

[0049] According to this design, for example, the following parameters can be used in the front chamber measurement mode with the same beam diameter at the scanner, the same scanner deflection and the same lens. 7 The anterior segment of the eye is scanned with an aperture of 0.033 within a range of + / -5.3mm around the optical axis: Focal length of the lens 7 of F = 30mm, distance of the lens 7 from the eye 5 3F = 90mm, distance from the scanner 6 to the lens 7 of 1F=30mm, a scanner mirror rotatable by + / -5 degrees with a diameter of approx. 3mm, prism 9 and deflecting angle mirror 10 in the beam path, a distance of the focus 16 from the scanner 6 of 1 / 2F = 15mm and a focal length of the lens 11 of F=75mm at a distance from the scanner 6 of 90mm.

[0050] A slightly different choice of distance between the lens and the lens can also be advantageous.7 to the scanner 6 in anterior chamber mode, so that the beam deflection in anterior chamber measurement mode can be designed to be divergent, telecentric, or convergent. In Figure 3 The images show slightly divergent scanning beams. Modifying the data above, this can be achieved, for example, with the following distances: Lens distance 7 to eye 5 from 94.5mm - 3F, scanner distance 6 to lens 7 from 25.5 - 1F and distance focus 16 to scanner 6 from 18.5mm - 1 / 2F.

[0051] The scanner is used in retina and anterior chamber modes with the same deflection and diameter, achieving an aperture of 0.025 at the anterior chamber and a lateral scan area of ​​+-7mm.

[0052] In this advantageous embodiment, the lenses or lens systems and distances are dimensioned such that the scan angles are as similar as possible in both measurement modes. It is important to ensure that the scan angles are large enough to capture the entire comea in the anterior chamber mode and the full visual field in the retinal mode.

[0053] In another embodiment, the scanner is smaller than the beam diameter at the eye in retina mode. For this purpose, a magnification M > 1 is selected in retina mode, e.g., M = 2, so that the beam diameter at the scanner is 1 mm and at the eye is 2 mm. The scan angle at the eye of + / -5 degrees can then be achieved with a scanner rotation angle of + / -5 degrees under the following conditions: distance eye 5 to lens 7 lens at a distance of 100mm 7 to scanner 6 of a 50mm focal length lens 7 of F = 100 / 3 = 33.33mm radius of the intermediate image 17of F = 100 / 6 = 16.66mm.

[0054] The anterior chamber mode with a scan field of + / -7mm and an aperture of 0.0125 at the eye is achieved by: distance eye 5 to lens 7 magnified to 119.25mm distance lens 7 to scanner 6 reduced to 30.75mm and distance of the focus 16 to the scanner 6 of 15.5mm.

[0055] The scanner's rotation angle of + / -5 degrees and the beam diameter at the scanner of 1 mm are exactly the same as in Retina mode. This is achievable with a non-telecentric, but slightly convergent beam path during scanning, as also in Figure 3 drawn. Furthermore, a particularly advantageous feature of this scale, which deviates from M=1, is the smaller installation space combined with a simultaneously increased distance to the eye.

[0056] The lens 7According to the invention, the lens can also consist of several parts, or can contain both a fixed and a movable lens part that is moved to switch between the modes.

[0057] In particular, the following fields can be reached in the two measurement modes: • anterior segment of the eye: covering the entire cornea, D=10mm to 20mm • posterior segment of the eye: 3° to 10° full viewing angle.

[0058] Furthermore, the focal lengths of the lenses or lens systems are preferably dimensioned such that the diameter of the OCT illumination beam on the scanner is minimized. This has the advantage that scanners with smaller mirrors can be used, allowing the OCT illumination beam to be moved faster and thus shortening the measurement time.

[0059] The invention was based on the objective of developing a device with two different measuring modes for the anterior (anterior chamber) and posterior (retina) segments of the eye, in which as few components as possible and as little installation space as possible are required for switching between them.

[0060] According to the invention, this is achieved by placing the focus of the OCT beam path in the anterior segment of the eye at a finite distance from the system exit point or on the anterior ocular media. In contrast, the focus of the OCT beam path in the posterior segment of the eye is at infinity, so that, for example, approximately collimated light is present at the system exit point, which is then focused onto the retina by the eye itself.

[0061] The problem of high mechanical complexity and installation space is solved here by not collimating the scanner, but focusing or diverging its illumination.

[0062] The proposed solution provides a device for measuring biometric parameters of the eye, enabling the biometric parameters relevant for calculating intraocular lenses to be determined quickly, reliably and reproducibly with the necessary accuracy and resolution.

[0063] Whole-eye scans make it possible to determine the position and profile of the areas of the entire eye that are relevant to the eye's vision.

[0064] The proposed device offers two different measurement modes for the anterior (anterior chamber) and posterior (retina) segments of the eye, requiring minimal technical effort and installation space. The distance between the eye and the device remains constant and does not need to be changed.

[0065] The proposed solution also has the advantage that the scanner is illuminated differently in the different measurement modes, so that a focus on the retina is achievable in the retina measurement mode.

Claims

1. Device for scanning measurement of the eye, consisting of an OCT arrangement (2) with an anterior chamber measurement mode and a retina measurement mode, characterized in that an optical element (7) which can be moved axially for switching between the modes is arranged between the x-y scanner (6) and the eye (5), and in that the x-y scanner (6) is illuminated convergently or divergently for switching between the modes.

2. Device according to Claim 1, characterized in that the x-y-scanner (6) is illuminated in focused fashion in the retina measurement mode, and the scanner pivot point is imaged into the pupil of the eye through the optical element, in that the optical element (7) is displaced towards the x-y-scanner (6) in the anterior chamber measurement mode, and the scanner is illuminated divergently.

3. Device according to Claims 1 to 2, characterized in that the optical element (7) in front of the x-y scanner (6) consists of 2 parts, at least one of which is designed to be axially displaceable.

4. Device according to Claim 1, characterized in that a first lens (7) in a position in the proximity of the scanner, a delay line (9, 10) and a second lens (12) are situated in the beam path in the anterior chamber measurement mode.

5. Device according to Claims 1 to 4, characterized in that the first and second lenses (7, 11 and 12) are dimensioned such that their distances and focal lengths are in a fixed relationship to each other.

6. Device according to Claims 1 to 4, characterized in that the first and second lenses are dimensioned such that the scanning angles are as equal as possible in both measurement modes.

7. Device according to Claim 6, characterized in that the scanning angles are so large in the anterior chamber measurement mode that the entire cornea is captured.

8. Device according to Claim 6, characterized in that the scanning angles are so large in the retina measurement mode that the full viewing angle is captured.

9. Device according to Claim 5, characterized in that the focal lengths of the first and second lenses are dimensioned such that the diameter of the OCT illumination beam on the scanner is minimized.