A subjective measurement system and method for corneal effective optical zone

Abstract

The present invention relates to a subjective measurement system for the effective optical zone of the cornea, the system comprising a parallel light source, a sight mark ring, a focusing system and a forehead support arranged in sequence, the parallel light source can provide parallel light, the parallel light source comprises a light source, a convex lens L1, a convex lens L2A, a pupil and a convex lens L2B arranged in sequence, the focusing system comprises a double lens L3A and a double lens L3B arranged in sequence, the forehead support can fix the head of the human eye so that the corneal surface positions of different testers are the same, the forehead support is arranged perpendicular to the optical axis; the sight mark ring, the double lens L3A and the double lens L3B can all move back and forth along the optical axis. The system of the present invention has low processing difficulty, simple operation, convenience and practicality. The method of the present invention abandons the method of estimating the effective optical zone of the human cornea using objective data, and adopts the corneal size when the sight mark ring stripes can be distinguished when actually measured by the real human eye as the effective optical zone.

Description

Technical Field

[0001] The invention belongs to the technical field of medical instruments, and in particular to a subjective measurement system and method for the effective optical zone of a cornea. Background Art

[0002] The effective optical zone (EOZ) of the cornea, also known as the functional optical zone (FOZ), refers to the area on the corneal surface that provides functional vision. It is the area with the smallest central corneal aberration and the best visual quality.

[0003] There is no specific standard for measuring the effective optical zone. According to previous studies, there are mainly the following methods for measuring and calculating the effective optical zone.

[0004] 1. Measurement using software based on the principle of ray tracing: This software is used to measure the spherical aberration of the cornea and pupil grating after laser assisted in situ keratomileusis (LASIK). This ray tracing system projects light onto the entire corneal topography interface and the imaginary detection plane (retina), and then uses mathematical calculations to calculate visual acuity. The effective optical zone is the diameter of the manually adjustable aperture measured when the simulated visual acuity reaches 20 / 32 [Boxer Wachler BS, Huynh VN, El Shiaty AF, et al. Evaluation of corneal functional optical zone afer laser insitu keratomileusis. J Cataract Refract Surg, 2002, 28(6): 948-953].

[0005] 2. Aberration calculation method: Tabernero et al. [Tabernero J, Klyce SD, Sarver EJ, et al. Functional optical zone of the cornea.. Invest Ophthal mol Vis SCI, 2007, 48 (3)] used the RMS value of corneal aberration and the modulation transfer function (MTF) corresponding to the corneal aberration to obtain the size of the effective optical zone of the cornea, and took the pupil diameter measured when the logMAR dropped to 0.2 as the threshold as the effective optical zone of the cornea. Camellin and Arba Mosquera [Camellin M, Arba Mosquera S. Aspheric optical zones: the effective optical zone with the SCHWINDAMARIS. J Refract Surg, 2011, 27(2): 135-1461 used a corneal wavefront aberrometer to study the size of the effective optical zone after two surface surgeries, laser epithelial keratomileusis (LASEK) and epipolis laser insitu keratomileusis (Epi LASIK). Corneal aberrations were converted into equivalent defocus and evaluated using three values: changes in the RMS value of corneal high-order aberrations, changes in spherical aberrations, and changes in high-order aberrations. On the corneal aberration difference map, the aberration value is recorded every 10 μm from the 4mm area of ​​the cornea to the periphery. When the aberration value changes by more than 0.25D, the corresponding diameter minus 10 μm is recorded as the effective optical zone.

[0006] 3. Corneal topography measurement method: The color difference of the color transition area between the ablation area and the non-ablation area on the corneal topography, or the difference in refractive power between the center and the periphery is measured. When the refractive power difference exceeds the specified value, the measured diameter is recorded as the effective optical zone of laser ablation. This method is more intuitive and commonly used in clinical practice. Holladay and Janes [Holladay JT, Janes JA. Topographic changes in corneal asphericity and effective optical zone afer laser insitukeratomileusis. J Cataract Refract Surg, 2002, 28 (6): 942-947] used the local curvature map of the corneal topography and used the color difference of 0.5D as the boundary of the optical zone. Qian et al. [Qian Y, Huang J, Zhou X. Corneal power distribution and functional optical zone Following small incision lenticule extraction for myopia. J Refract Surg, 2015, 31 (8): 532-538] defined the effective optical zone as the diameter of the largest corneal ring within 8 mm on the refractive power distribution diagram when the difference between the average refractive power and the pupil center refractive power exceeds 1.5 D. Racine et al. [Racine L, Wang L, Koch DD. Size of corneal topographic effective optical zone: comparison of standard and customized myopic laser in situkeratomileusis. Am J Ophthalmol, 2006, 142 (2): 227-232] measured the effective optical zone before and after wavefront-guided LASIK surgery and standard LASIK surgery by area. This study depicted the ablation profile in the area where the corneal curvature changed more than 0.5D in the refractive power interface of the Humphrey Atlas corneal topography, measured the major and minor axes of the ellipse, and calculated the area of ​​the ellipse as the effective optical zone.

[0007] These methods all use instruments to measure corneal topography, aberration and other parameters, and set universal evaluation criteria to obtain an objective effective optical zone, without considering the actual visual characteristics of the real human eye.

[0008] Through searching, no patent publication documents related to the patent application of the present invention have been found. Summary of the invention

[0009] The purpose of the present invention is to overcome the shortcomings of the prior art that the effective optical zone of the cornea is measured objectively and cannot reflect the real visual characteristics of the human eye, and to provide a subjective measurement system and method for the effective optical zone of the cornea.

[0010] The technical solution adopted by the present invention to solve its technical problem is:

[0011] A subjective measurement system for corneal effective optical zone, the system comprising a parallel light source, a sight mark ring, a focusing system and a forehead rest arranged in sequence, the parallel light source can provide parallel light, the parallel light source comprises a light source, a convex lens L1, a convex lens L2A, a pupil and a convex lens L2B arranged in sequence, the focusing system comprises a double lens L3A and a double lens L3B arranged in sequence, the forehead rest can fix the head of a human eye so that the corneal surface positions of different testers are the same, and the forehead rest is arranged perpendicular to the optical axis;

[0012] The sight mark ring, the double lens L3A and the double lens L3B can all move back and forth along the optical axis;

[0013] The light source is arranged at the focus of the convex lens L1, the pupil plane is arranged on the focal plane of the convex lens L2A and the convex lens L2B, the light source, the convex lens L1, the convex lens L2A, the pupil, the convex lens L2B, the sight mark ring, the double lens L3A, the double lens L3B and the center of the pupil of the human eye are all on the optical axis of the system, and the corneal plane of the human eye is conjugate with the sight mark ring plane.

[0014] Moreover, the light source, convex lens L1, convex lens L2A and convex lens L2B form a parallel light pipe to provide parallel light for the system.

[0015] Moreover, the light source emits light in parallel with an error of ±0.01D.

[0016] Moreover, the convex lens L1 is a refractive-diffractive hybrid system, the diffractive surface adopts a binary surface, and uses 8 steps to fit a π optical path. Within the diameter of 26 mm, the parameters are A1=-631.6, A2=83, and A3=48.6;

[0017] Alternatively, the convex lens L1 is a double cemented lens made of two types of glass, F2 and BK7, with a diameter of φ25 mm, a thickness Tc=18 mm, and a curvature radius f' which is the distance from the light source to the center of the lens.

[0018] Moreover, the light source is a laser white light source, and the light passes through the convex lens L1, the central part is parallel light, and then passes through the convex lens L2A, the parallel light passes through the pupil at the focus, and becomes parallel light again at L2B, and the stray light is blocked by the pupil;

[0019] Alternatively, the light source is a laser with a pinhole structure in front, and then passes through convex lens L1, convex lens L2A and convex lens L2B to obtain a parallel light source.

[0020] Moreover, the sight mark ring is a circular ring with sight marks, the circular ring is equally distributed, the sight mark corresponding viewing angle is adjustable, and the typical value is 20 / 32; the circular ring is designed with light and dark sight marks, the sight mark spacing is tan(1 / (60x)), and x is the visual acuity.

[0021] Moreover, the focusing system is a dual-lens focusing system. When the human eye is emmetropic, the focusing system is a parallel light delay device and has no focusing effect. When the human eye is myopic, the dual lens L2A is moved along the optical axis, and the focusing system becomes negative refraction to balance the refractive power of the human eye. When the human eye is hyperopic, the dual lens L2A is moved along the optical axis, and the focusing system becomes positive refraction.

[0022] The measurement system as described above is used for measuring the effective optical zone of the cornea.

[0023] The subjective measurement method for measuring the effective optical zone of the cornea using the measurement system described above is as follows:

[0024] ⑴ Equipment calibration

[0025] Place the simulated eye for calibration on the forehead rest to determine whether the system can focus. The specific steps are as follows:

[0026] ① Without adding a sight mark ring in the optical path, the focus is determined based on the size of the image spot of the CCD detector; the determination method is: the image spot is smaller than 13 microns; if it is focused, proceed to the next step; if it is not focused, the equipment is stopped and needs to be repaired;

[0027] ② Add a sight mark ring in the optical path, form an image with the CCD detector, and read the sight mark ring image. The fringe contrast is defined as the ratio of the average grayscale of the bright fringe to the average grayscale of the dark fringe. If the fringe contrast is greater than 50, it is judged to be qualified and can proceed to the next step. Otherwise, the equipment will be stopped from use.

[0028] ⑵Measurement

[0029] The tester places his chin on the forehead rest and looks at the sight mark ring. The sight mark ring changes from outside to inside until the sight mark can just be distinguished. The measurement is then completed. At this point, the area of ​​the sight mark ring is the effective optical zone of the cornea.

[0030] Moreover, the calibration simulated eye includes a cancellation lens L4, a CCD detector and a computer which are connected in sequence, the focal length is equal to the distance from the lens center of the cancellation lens L4 to the detection surface of the CCD detector, the cancellation lens L4 can simultaneously eliminate chromatic aberration and spherical aberration, the CCD detector can form an image, and the screen of the computer can display the image of the CCD detector.

[0031] The advantages and positive effects achieved by the present invention are:

[0032] 1. The system of the present invention has low processing difficulty, simple operation, convenience and practicality.

[0033] 2. The system of the present invention adopts a refractive-diffractive hybrid system and a reflective system to repeatedly eliminate the influence of chromatic aberration.

[0034] 3. The sight mark ring of the system of the present invention is adjustable and can be suitable for measuring the effective optical zone of the cornea corresponding to different visual acuities.

[0035] 4. The method of the present invention abandons the method of estimating the effective optical zone of the human cornea using objective data, and adopts the corneal size that can distinguish the sight mark ring stripes actually measured by the real human eye as the effective optical zone.

[0036] 5. The method of the present invention adopts subjective measurement, which fully considers the reality of human vision. The measured value is a true reflection of the visual characteristics of the human eye. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 A structural connection schematic diagram of the system of the present invention;

[0038] Figure 2 A schematic diagram of the structural connection of the refractive-diffractive hybrid system of the present invention;

[0039] Figure 3 FIG. 1 is a schematic diagram of a structural connection of an achromatic doublet lens in the present invention; wherein Tc is the center thickness, Te is the edge thickness, is the lens radius, f' is the radius of curvature;

[0040] Figure 4 A schematic diagram of the structural connection of the sight mark ring in the present invention;

[0041] Figure 5 A schematic diagram of the structural connection of a simulated eye for calibration in the present invention;

[0042] Figure 6 The figure is a schematic diagram of a structural connection of a binary surface etched on the surface of an aspheric lens in the present invention. DETAILED DESCRIPTION

[0043] The present invention will be further described below in conjunction with the embodiments. The following embodiments are descriptive rather than restrictive, and the protection scope of the present invention cannot be limited by the following embodiments.

[0044] The structures used in the present invention are all conventional structures unless otherwise specified; the methods used in the present invention are all conventional methods in the art unless otherwise specified.

[0045] A subjective measurement system of the corneal effective optical zone, such as Figure 1As shown, the system includes a parallel light source, a sight mark ring, a focusing system and a forehead rest which are arranged in sequence and at intervals. The parallel light source can provide parallel light. The parallel light source includes a light source, a convex lens L1, a convex lens L2A, a pupil and a convex lens L2B which are arranged in sequence and at intervals. The focusing system includes a double lens L3A and a double lens L3B which are arranged in sequence and at intervals. The forehead rest can fix the head of a human eye so that the corneal surface positions of different testers are the same. The forehead rest is arranged perpendicular to the optical axis.

[0046] The sight mark ring, the double lens L3A and the double lens L3B can all move back and forth along the optical axis;

[0047] The light source is arranged at the focus of the convex lens L1, the pupil plane is arranged on the focal plane of the convex lens L2A and the convex lens L2B, the light source, the convex lens L1, the convex lens L2A, the pupil, the convex lens L2B, the sight mark ring, the double lens L3A, the double lens L3B and the center of the pupil of the human eye are all on the optical axis of the system, and the corneal plane of the human eye is conjugate with the sight mark ring plane.

[0048] In this embodiment, the light source, convex lens L1, convex lens L2A and convex lens L2B form a parallel light pipe to provide parallel light for the system.

[0049] Preferably, the light source emits light in parallel with an error of ±0.01D.

[0050] Preferably, in order to reduce the influence of chromatic aberration, the convex lens L1 is a refractive-diffractive hybrid system, the diffraction surface adopts a binary II surface, and 8 steps are used to fit a π optical path. Within the diameter of 26 mm, the parameters are A1=-631.6, A2=83, and A3=48.6, which can be as follows: Figure 2 shown.

[0051] Alternatively, the convex lens L1 is a double cemented lens, made of two kinds of glass, F2 and BK7 (the connection relationship between the two is not limited, as long as one is F2 and the other is BK7), with a diameter of φ25 mm, a thickness Tc=18 mm, and a curvature radius f' being the distance from the light source to the center of the lens, which can be as follows: Figure 3 shown.

[0052] In this embodiment, the light source is a laser white light source. The light passes through the convex lens L1, the central part is parallel light, and then passes through the convex lens L2A. The parallel light passes through the pupil at the focus and becomes parallel light again at L2B. The stray light is blocked by the pupil.

[0053] Preferably, the pupil diameter is 1 mm.

[0054] In this embodiment, the light source may also be a laser with a pinhole structure in front, and then pass through convex lens L1, convex lens L2A and convex lens L2B to obtain a parallel light source.

[0055] In this embodiment, the sight mark ring is a circular ring with sight marks. The circular rings are equally distributed, and the sight marks are adjustable in angle of view, with a typical value of 20 / 32. The circular rings are designed with light and dark sight marks, and the sight mark spacing is tan(1 / (60x)), where x is the visual acuity. For example, for 20 / 32, the axial length of the human eye is 24mm, and the spacing L is 0.64mm. R1 and R2 have typical values ​​in the embodiments, which can be as follows Figure 4 shown.

[0056] In this embodiment, the focusing system is a dual-lens focusing system. When the human eye is emmetropic, the focusing system is a parallel light delay device and has no focusing effect. When the human eye is myopic, the dual lens L2A is moved along the optical axis, and the focusing system becomes negative refraction to balance the refractive power of the human eye. When the human eye is hyperopic, the dual lens L2A is moved along the optical axis, and the focusing system becomes positive refraction.

[0057] When the system is in use, parallel light passes through the annular sight mark, enters the focusing system, reaches the surface of the cornea, then passes through the human eye optical system, and finally forms an image on the retina to be perceived by the human eye.

[0058] The subjective measurement method for measuring the effective optical zone of the cornea using the measurement system described above is as follows:

[0059] 1. Equipment calibration

[0060] Place the simulated eye for calibration on the forehead rest to determine whether the system can focus. The specific steps are as follows:

[0061] (1) Without adding a sight mark ring in the optical path, the focus is determined based on the size of the CCD detector image spot. The determination method is: if the image spot is smaller than 13 microns, the next step is carried out. If it is not focused, the equipment is stopped and needs to be repaired.

[0062] (2) A sight mark ring is added to the optical path, the CCD detector forms an image, and the sight mark ring image is read. The fringe contrast is defined as the ratio of the average grayscale of the bright fringe to the average grayscale of the dark fringe. If the fringe contrast is greater than 50, it is judged to be qualified and the next step can be carried out. Otherwise, the equipment is stopped from use.

[0063] 2. Measurement

[0064] The tester places his chin on the forehead rest and looks at the sight mark ring. The sight mark ring changes from outside to inside until the sight mark can just be distinguished. The measurement is then completed. At this point, the area of ​​the sight mark ring is the effective optical zone of the cornea.

[0065] Specifically, Figure 5As shown, the calibration simulated eye includes a cancellation lens L4, a CCD detector and a computer which are connected in sequence, the focal length is equal to the distance from the lens center of the cancellation lens L4 to the detection surface of the CCD detector, the cancellation lens L4 can simultaneously eliminate chromatic aberration and spherical aberration, the CCD detector can form an image, and the screen of the computer can display the image of the CCD detector.

[0066] The function of the simulated eye for calibration is to determine whether the system can form a focus, so as to prevent the system of the present invention from making mistakes and causing mismeasurements.

[0067] Preferably, L4 is an absorptive lens, which is an optical component that can eliminate chromatic aberration and spherical aberration at the same time. The purpose is to eliminate first-order chromatic aberration and first-order spherical aberration in the visible light range by etching a binary surface on the surface of the aspheric lens, such as Figure 6 As shown. The function of the binary surface is to eliminate the first-order chromatic aberration of this lens. The function of the aspherical surface is to eliminate the first-order spherical aberration.

[0068] Specifically, the relevant preparation and detection are as follows:

[0069] The subjective measurement system of the present invention is used. A high-brightness laser white light source purchased on the market is used, which is composed of a chip and a phosphor, with a color temperature of 6465K and a model of osramW 5050. The GaN-based blue chip emits blue light, and the phosphor absorbs part of the blue light to emit yellow-green light, and white light is obtained after mixing. The light-emitting surface is circular, and the diameter of the light source chip is 100 microns.

[0070] The collimator is composed of two refractive lenses with a focal length of 200 mm and the binary surface parameters as described above.

[0071] The standard eye focal length is 200mm. It is a triple cemented aspheric lens made of N-SF8 and N-BAF52. The aspheric surface adopts Even aspheric surface type. The second-order coefficient is 81, and the fourth-order coefficient is -16.

[0072] There are 10 sight mark rings in total, which are silver iodide films obtained by laser exposure method.

[0073] The outer ring radii of the 10 images are as follows:

[0074]

[0075] The first one is the central bright circle, the inner ring radius of the second one is the outer ring radius of the first one, the inner ring radius of the nth one is the outer ring radius of the n-1th one, 1 <n<=10。

[0076] Black and white stripes are evenly distributed within the white ring, with an interval of 0.2632 mm, corresponding to a visual acuity of 20 / 32.

[0077] The lenses were placed in the optical path one by one from number 1 to 10. A volunteer was asked to observe the black line and found that the black line could not be distinguished after the sixth change, and the diameter of the effective optical zone of the cornea was 6.364 mm.

[0078] Although the embodiments of the present invention are disclosed for illustrative purposes, those skilled in the art will appreciate that various substitutions, changes and modifications are possible without departing from the spirit and scope of the present invention and the appended claims. Therefore, the scope of the present invention is not limited to the contents disclosed in the embodiments.

Claims

1. A subjective measurement system for the effective optical zone of the cornea, characterized in that: The system includes a parallel light source, a sight mark ring, a focusing system and a forehead rest which are arranged in sequence and at intervals. The parallel light source can provide parallel light. The parallel light source includes a light source, a convex lens L1, a convex lens L2A, a pupil and a convex lens L2B which are arranged in sequence and at intervals. The focusing system includes a double lens L3A and a double lens L3B which are arranged in sequence and at intervals. The forehead rest can fix the head of a human eye so that the corneal surface positions of different testers are the same. The forehead rest is arranged perpendicular to the optical axis. The sight mark ring, the double lens L3A and the double lens L3B can all move back and forth along the optical axis; The light source is arranged at the focus of the convex lens L1, the pupil plane is arranged on the focal plane of the convex lens L2A and the convex lens L2B, the light source, the convex lens L1, the convex lens L2A, the pupil, the convex lens L2B, the sight mark ring, the double lens L3A, the double lens L3B and the center of the pupil of the human eye are all on the optical axis of the system, and the corneal plane of the human eye is conjugate with the sight mark ring plane; The convex lens L1 is a refractive-diffractive hybrid system, the diffractive surface is a binary surface, 8 steps are used to fit a π optical path, within a diameter of 26 mm, the parameters are A1=-631.6, A2=83, A3=48.6; Alternatively, the convex lens L1 is a double cemented lens made of two types of glass, F2 and BK7, with a diameter of mm, thickness Tc = 18 mm, radius of curvature f' is the distance from the light source to the center of the lens; The light source is a laser white light source. The light passes through the convex lens L1, and the central part is parallel light. Then it passes through the convex lens L2A, and the parallel light passes through the pupil at the focus, and becomes parallel light again at L2B. The stray light is blocked by the pupil. Alternatively, the light source is a laser with a pinhole structure in front, and then passes through convex lens L1, convex lens L2A and convex lens L2B to obtain a parallel light source.

2. The subjective measurement system of corneal effective optical zone according to claim 1, characterized in that: The light source, convex lens L1, convex lens L2A and convex lens L2B form a parallel light pipe to provide parallel light for the system.

3. The subjective measurement system of corneal effective optical zone according to claim 1, characterized in that: The light source emits light in parallel, and the error 0.01 D.

4. The subjective measurement system of corneal effective optical zone according to claim 1, characterized in that: The sight mark ring is a circular ring with sight marks, the circular ring is equally distributed, the sight mark corresponding viewing angle is adjustable, and the typical value is 20 / 32; the circular ring is designed with light and dark sight marks, and the sight mark spacing is tan(1 / (60x)), where x is the visual acuity.

5. The subjective measurement system of the corneal effective optical zone according to any one of claims 1 to 4, characterized in that: The focusing system is a dual-lens focusing system. When the human eye is emmetropia, the focusing system is a parallel light delay device and has no focusing function. When the human eye is myopic, the double lens L2A is moved along the optical axis, and the focusing system becomes negative refraction to balance the refractive power of the human eye; when the human eye is hyperopic, the double lens L2A is moved along the optical axis, and the focusing system becomes positive refraction.

6. A subjective measurement method for measuring the effective optical zone of the cornea using the measurement system according to any one of claims 1 to 4, characterized in that: Here are the steps: ⑴ Equipment calibration Place the simulated eye for calibration on the forehead rest to determine whether the system can focus. The specific steps are as follows: ① Without adding sight mark ring in the optical path, the focus is determined based on the image spot size of the CCD detector; determination method: if the image spot is smaller than 13 microns; if it is focused, proceed to the next step; if it is not focused, the equipment is stopped and needs to be repaired; ② Add a sight mark ring in the optical path, image the CCD detector, and read the sight mark ring image. The fringe contrast is defined as the ratio of the average grayscale of the bright fringe to the average grayscale of the dark fringe. If the fringe contrast is greater than 50, it is judged to be qualified and can proceed to the next step. Otherwise, the equipment will stop using. ⑵Measurement The tester places his chin on the forehead rest and looks at the sight mark ring. The sight mark ring changes from outside to inside until the sight mark can just be distinguished. The measurement is then completed. At this point, the area of ​​the sight mark ring is the effective optical zone of the cornea.

7. The subjective measurement method for measuring the effective optical zone of the cornea by the measurement system according to claim 6, characterized in that: The calibration simulated eye includes a cancellation lens L4, a CCD detector and a computer which are connected in sequence, the focal length is equal to the distance from the lens center of the cancellation lens L4 to the detection surface of the CCD detector, the cancellation lens L4 can simultaneously eliminate chromatic aberration and spherical aberration, the CCD detector can form an image, and the screen of the computer can display the image of the CCD detector.

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