CN114779497A - A scleral contact lens based on phase modulation technology - Google Patents

Abstract

The scleral contact lens based on the phase modulation technology proposed by the present invention can individually modulate the wavefront aberration of the whole eye by superimposing the modulation/demodulation phase on the optical surface of the front surface of the scleral contact lens, so as to meet the design requirements. It can accurately compensate various wavefront distortions on the anterior surface of the cornea of the patient, and greatly improve the vision level and visual quality of the patient.

Description

A scleral contact lens based on phase modulation technology

technical field

The invention relates to the technical field of scleral contact lenses, in particular to a scleral contact lens based on phase modulation technology.

Background technique

The scleral lens is a specially designed rigid gas permeable contact lens. It is named for the large diameter of the lens, which does not contact the cornea, spans the entire cornea, and touches the sclera area. Large-diameter contact lenses allow the lens to be positioned beyond the corneal limbus, making it considered the best way to correct vision in patients with irregular corneas. For the cornea, there is a real gap when wearing a scleral lens without any mechanical friction. , Try to avoid any contact between the lens and the cornea, so that the lens spans the cornea like a bridge, as shown in Figure 1. Technically, these lenses are not contact lenses, at least not in contact with the surface of the cornea, and the comfort of the cornea is greatly improved, which is one of the biggest advantages of large diameter contact lenses.

In recent years, scleral lenses have become more and more popular in Europe and the United States. Because of their personalized design, they have certain advantages for the treatment of refractive correction, irregular cornea, and dry eye. According to the diameter of scleral lenses, it can be divided into corneoscleral lenses (diameter 12.5mm-15mm, touching part of the cornea), mini scleral lenses (diameter 15mm-18mm, fully touching the sclera), full scleral lenses (18mm-25mm, fully touching the sclera) ), because the tear storage capacity of mini scleral lens is usually small, it has good oxygen permeability and visual quality, and has better corneal apex space, which can reduce the mechanical friction on the central cornea.

The scleral lens adopts the gas permeable rigid gas permeable scleral contact lens material, that is, the RGP material with high oxygen permeability is gradually improved to form materials with different oxygen permeability coefficients. The current lens materials are mainly from BOSTON, Menicon and CONTAMAC. BOSTON material is currently the material with the largest amount, the most common use, and the largest number of users in the world. It has high oxygen permeability and humidity, and the comfort is also good. Among them, the BOSTON XO2 material has a wetting angle of 38 and an oxygen permeability coefficient of 141. Dk value, good dimensional stability and processability, the material has been applied to rigid gas permeable contact lenses for orthokeratology, its safety and effectiveness have been verified, its high oxygen permeability and balanced processability It has become an ideal material for the preparation of scleral lenses. Scleral lenses require the use of high Dk materials and there should not be too much tear in the lens-corneal space to prevent hypoxia. Research shows that there is no current study to prove that wearing modern scleral lenses can lead to corneal hypoxia.

The clinical application of scleral lenses generally uses try-on lenses and try-on evaluation techniques. The main fitting process is: first, corneoscleral topography, slit lamp examination, and OCT anterior segment examination. Obtain the sagittal height from the vertex of the cornea to the landing zone and the corresponding sagittal height difference, and select a suitable try-on lens for try-on evaluation; hold the lens with a suction rod before wearing, and the lens is filled with saline and sodium fluorescein, and the patient is asked to bow his head vertically Looking at the ground, use your own hands to open the upper and lower eyelids as much as possible to expose the eyeballs. The doctor helps the patient put on the lenses and observes whether there are air bubbles under the lenses. When wearing scleral lenses, the lens movement is almost zero, and there is almost no tear exchange. The ideal apex tear film gap is about 300 microns, there will be slight depression on the sclera when the edge of the lens touches the sclera, and the thickness of the tear layer is significantly reduced after wearing (120-170 microns). To assess the tear thickness between the lens and the cornea, a slit lamp can be used to observe the tear thickness under the lens at a 45-degree angle by light sectioning (fluorescence staining is optional). The corneal limbus should be 360-degree fluorescent filling under slit lamp observation, avoid direct contact between the lens and the corneal limbus, and the edge of the lens should not oppress the bulbar conjunctival blood vessels. The limbus is very important for corneal health, especially stem cells are responsible for generating new epithelial cells that are dispersed throughout the cornea. The tear fluid between the lens and the limbus is very important for the fragile stem cells of the limbus. During fitting, try to ensure that there is a space of about 100 microns in the limbus. It is recommended to use OCT as an auxiliary tool during fitting. From the central apex to the limbus, the tear thickness that should be retained at each location can be accurately assessed to improve the accuracy of fitting.

It is also important to assess the pressure exerted by the lens positioning arc on the bulbar conjunctiva. If the positioning area is too compressed on the conjunctiva, the blood in the compressed area of the conjunctiva will not be able to pass through the blood vessels, causing the conjunctival blood vessels under the lens to whiten. In addition, scleral lenses also need to be tilted to help tear circulation. However, the warping angle should not be too high. Too high warping angle will increase the foreign body sensation, and it is easy to feel uncomfortable when wearing it, which affects the wearing comfort. The warping angle can be adjusted by changing the angle of the positioning area. Finally, the subjective refraction and visual acuity examination after wearing the glasses were carried out to determine the diopter of the lenses.

In general, rigid scleral contact lenses have the following unique advantages: (1) The high oxygen permeability ensures sufficient oxygen on the surface of the eye, which greatly reduces complications compared with ordinary soft lenses, and is currently one of the safest contact lenses to wear. One; (2) It has good forming effect and good optical performance, which ensures that you can get clear vision, even high astigmatism, irregular astigmatism, and aphakia will be well corrected; (3) In addition, the adaptation of scleral lenses The symptoms are quite extensive: general myopia, hyperopia, astigmatism, anisometropia; especially high myopia, high hyperopia, high astigmatism, irregular astigmatism; keratoconus or presbyopia, due to various refractive corneal surgeries (such as RK, Irregular astigmatism caused by PRK, LASIK), corneal transplantation, corneal diseases (such as corneal trauma, keratitis); wearer.

Compared with soft lenses and frame glasses, the key reason why scleral contact lenses can significantly improve the visual quality of the human eye is that a layer of several hundred microns of tear layer is formed between the anterior surface of the cornea and the posterior surface of the scleral lens. The refractive index of the cornea is similar to the refractive index of the cornea itself, so it can significantly reduce the wavefront aberration changes caused by various defects and deformations on the anterior surface of the cornea, and improve the visual quality of patients. The optical area of scleral contact lenses is a simple spherical design. Although the visual quality is improved to a certain extent, many patients will still experience glare and unclear vision after wearing them, especially when the pupils become larger at night. , The main reason is that patients who wear scleral lenses, under normal circumstances, the condition of the cornea is relatively poor, there are irregular astigmatism or regular high astigmatism, and some even have higher order aberrations such as coma and clover, these The existence of higher-order aberrations greatly limits the further improvement of patients' visual quality. Therefore, it is urgent to develop a scleral contact lens based on phase modulation technology to solve the above technical problems.

In view of this, the present invention is proposed.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a scleral contact lens based on phase modulation technology. First, a three-dimensional sagittal height distribution model of the anterior surface of the human cornea is established, and secondly, based on the classic LB human eye model, an optical system of the human eye after wearing the scleral contact lens is established. The model, thirdly, the rear surface of the scleral lens adopts a spherical design, which mainly matches the curvature radius of the surface of the human eye. Finally, according to the wavefront aberration that actually exists in the whole eye, the superimposed phase modulation function is in the optical area of the front surface of the scleral lens, and the incident field of view is different for each incident field of view. The specific optical aberration is modulated to achieve the balance or correction of the target aberration.

In view of the above problems existing in the prior art, the present invention provides a scleral contact lens based on phase modulation technology. The inner surface of the scleral contact lens (the surface in contact with the cornea) can be generally divided into three parts from the middle to the outside. Part: intermediate optical zone D1, transition zone D2 and landing zone D3, as shown in Figure 2, characterized in that the optical zone spans the cornea and does not contact the cornea to correct vision; the transition zone connects the optical zone and the landing zone, located in the Corneal limbus is divided into two areas: limbal adaptation area and limbal area. The limbal area is located at the corneal limbus and maintains a certain gap with the corneal limbus. The marginal adaptation area is used to adjust the sagittal height of the scleral lens and compensate for the sagittal height; landing The contact lens area is the load-bearing area of the entire lens, which should be consistent with the curvature of the sclera and contact the sclera tangentially, so that the scleral contact lens can be well fixed on the sclera, and the landing area forms an angle with the cornea, which is conducive to the exchange of tears.

The anterior surface optical zone of the scleral contact lens and the inner surface optical zone of the scleral lens jointly provide optical imaging characteristics. Additional phase term defined by Zernike standard coefficients. The additional phase term deviates and increases the ray's optical path as it passes through the surface. This surface type actually adds phase modulation to the standard surface type, and the additional phase of the surface is defined as:

The phase function describes the modulation of the phase by increasing the modulation phase at any radial wavelength position on the basis of the standard surface. The standard surface shape (basal shape) of the optical zone of the front surface of the scleral contact lens adopts the design of the bicubic surface with a high-order term, and is expressed by the following formula:

in,

In addition to the base radius, the high-order coefficients of the conic coefficient can be different in the X and Y directions. α _i and β _i are the high-order aspheric coefficients in the x and y directions, respectively. The biquad surface allows to directly specify Rx, Ry , Kx and Ky.

The surface shape of the optical zone of the front surface of the scleral contact lens, that is, the surface shape distribution after phase modulation is expressed as:

The first term is the basal surface profile, which together with the posterior surface of the scleral lens provides the power of the scleral contact lens, the next two are the high-order aspheric coefficients in the x and y directions, and the last term is superimposed on the basal surface. phase modulation term above.

For the scleral contact lens, the face shape distribution of the human cornea is measured with a corneal topograph, to obtain the sag height distribution map of the corneal front surface shape, fit the equivalent radius of curvature and the conic coefficient, and use the Zernike for the sag height difference. Sag coefficient expansion:

For the scleral contact lens, the discretely sampled surface shape of the anterior surface of the cornea can also be directly converted into a phase surface, and the conversion method is as follows:

The sag distribution of the anterior corneal surface is discretized on the two-dimensional xy plane, Δy is the sag of the anterior corneal sag at the Δx displacement interval, and the phase of the sag distribution can be directly transformed.

After simulated wearing of the scleral contact lens, an imaging optical system of the human eye after wearing the lens is established, and the ray tracing method is used to calculate the retinal defocus distribution when the on-axis field of view and the off-axis field of view are incident. The weighted sum of the RMS values of the field of view is used as an evaluation function. The smaller the value, the better the imaging quality, namely:

The scleral contact lens is characterized in that the whole adopts plasma treatment to improve the hydrophilicity of the surface, making it more comfortable to wear, and the plasma power is 10-2000W.

The scleral contact lens has a refractive index range of 1.4-1.6, and an oxygen permeability coefficient of (80-200)*10-11 (cm ² /s) [mlO ₂ /(ml×mmHg)].

The total diameter of the scleral contact lens is in the range of 12.5mm-24mm, and the radius of curvature of the rear surface is in the range of 6.4mm-9.2mm.

Design method:

(1) The corneal topography instrument is used to obtain information such as the curvature, thickness, and depth of the anterior chamber of the human cornea. The most important thing is that the aspheric coefficient Q of the human cornea can be obtained individually.

(2) The sag height distribution data of the anterior corneal surface obtained by the corneal topograph, establish a model of the sag height distribution of the anterior corneal surface of the human eye, and use the fitting algorithm to obtain the difference between the actual surface sag height minus the fitted sag height, and the residuals are calculated. Zernike polynomial expansion, and finally get the expression for the front surface sag.

(3) Convert the corneal anterior surface sag into phase distribution data, import it into the personalized human eye model, and establish a complete personalized human eye model including the actual corneal anterior surface.

(4) Based on the personalized human eye model, establish the optical system model of the human eye after wearing the scleral contact lens, establish on-axis and different off-axis rays, and perform ray tracing, as shown in Figure 3.

(5) The posterior surface of the scleral lens is matched with the anterior surface of the human cornea, and the radius is slightly flatter than the average curvature radius of the anterior surface of the cornea.

(6) Obtain the distribution characteristics and amplitudes of wavefront aberrations under different pupil conditions of the whole eye through individualized ray tracing of the human eye, and provide the aberration values for targeted phase modulation and compensation according to the actual needs of patients;

(7) For the wavefront aberration actually existing in the whole eye, superimpose the phase modulation function in the optical area of the front surface of the scleral lens to modulate the specific optical aberration of each incident field of view to achieve the balance or correction of the target aberration.

(8) Determine the final profile of the anterior surface of the scleral lens.

(9) Lathe, polishing. The raw material used for processing is high oxygen permeability material, the material reaches glass state at room temperature, and the front and rear surfaces are processed by diamond single-point turning processing technology. Single-end polishing removes driveway lines and minor scratches.

(10) After plasma treatment, the surface is hydrophilic and more comfortable to wear. The plasma power is 10-2000W.

The scleral contact lens based on the phase modulation technology provided by the present invention can individually modulate the wavefront aberration of the whole eye by superimposing the modulation/demodulation phase on the optical surface of the front surface of the scleral contact lens, and has the following beneficial effects :

1. Meet the requirements for human eye wavefront aberration during design.

2. Accurately compensate various wavefront distortions on the anterior surface of the patient's cornea.

3. Greatly improve the patient's vision level and visual quality.

Description of drawings

1 is a schematic diagram of a human eye wearing a scleral contact lens;

Figure 2 is a schematic structural diagram of a scleral contact lens;

Fig. 3 is the human eye ray tracing diagram of scleral contact lens;

Fig. 4 is the design flow chart of the scleral contact lens based on phase modulation technology;

Figure 5. Comparison of Zernike coefficients before and after the modulation of the central field of view under the 6mm pupil. The spherical surface is before modulation and the aspherical surface is after modulation;

Fig. 6 Comparison of Zernike coefficients before and after 5-degree field of view modulation under the 6mm pupil, the spherical surface is before modulation and the aspherical surface is after modulation;

Fig. 7 Comparison of Zernike coefficients before and after 10-degree field of view modulation under 6mm pupil, the spherical surface is before modulation and the aspherical surface is after modulation;

Figure 8 is a comparison of MTF before and after 6mm pupil, 0 degree field of view modulation;

Figure 9 is a comparison of MTF before and after 6mm pupil, 5 degree field of view modulation;

Figure 10 is a comparison of MTF before and after 6mm pupil, -5 degree field of view modulation.

Detailed ways

The present invention will be further described below with reference to specific embodiments and accompanying drawings to help understand the content of the present invention.

Example 1

As shown in Figure 2, which is a schematic diagram of the structure of the scleral contact lens, the inner surface of the scleral contact lens (the surface in contact with the cornea) can be generally divided into three parts from the middle to the outside: the intermediate optical zone D1, the transition zone D2 and the landing zone Zone D3, the anterior surface optical zone of the scleral contact lens and the scleral lens inner surface optical zone together provide optical imaging properties.

The preparation steps of the scleral contact lens are as follows, and the design flow chart is shown in Figure 4:

(1) The corneal topography instrument is used to obtain information such as the curvature, thickness, and depth of the anterior chamber of the human cornea. The most important thing is that the aspheric coefficient Q of the human cornea can be obtained individually.

(2) The sag height distribution data of the anterior corneal surface obtained by the corneal topograph, establish a model of the sag height distribution of the anterior corneal surface of the human eye, and use the fitting algorithm to obtain the difference between the actual surface sag height minus the fitted sag height, and the residuals are calculated. Zernike polynomial expansion, and finally get the expression for the front surface sag.

(3) Convert the corneal anterior surface sag into phase distribution data, import it into the personalized human eye model, and establish a complete personalized human eye model including the actual corneal anterior surface.

(4) Based on the personalized human eye model, establish the optical system model of the human eye after wearing the scleral contact lens, establish on-axis and different off-axis rays, and perform ray tracing, as shown in Figure 3.

(5) The posterior surface of the scleral lens is matched with the anterior surface of the human cornea, and a radius that is flatter than the average curvature radius of the anterior surface of the cornea is adopted, and a spherical design is adopted to match the curvature radius of the anterior surface of the human cornea.

(6) Obtain the distribution characteristics and amplitudes of wavefront aberrations under different pupil conditions of the whole eye through individualized ray tracing of the human eye, and provide the aberration values for targeted phase modulation and compensation according to the actual needs of patients;

(7) For the wavefront aberration actually existing in the whole eye, superimpose the phase modulation function in the optical area of the front surface of the scleral lens to modulate the specific optical aberration of each incident field of view to achieve the balance or correction of the target aberration.

(8) Determine the final profile of the front surface of the scleral lens, lathe and polish. The raw material used for processing is high oxygen permeability material, the material reaches glass state at room temperature, and the front and rear surfaces are processed by diamond single-point turning processing technology. Single-end polishing removes driveway lines and minor scratches.

(9) After plasma treatment, the surface is hydrophilic and more comfortable to wear. The plasma power is 10-2000W.

Analysis and discussion of the results:

Using the ray tracing software, combined with the established personalized human eye model, the distribution of on-axis and off-axis light rays in the retina of the human eye is obtained, as shown in Figure 3. It can be seen from the figure that the diopter error of the on-axis point has been corrected, the light is focused on the retina, and then the off-axis light is focused in front or behind the retina, and the number of Zeniko terms modulated by the target is the astigmatism term Z5 of the 6mm pupil respectively. and Z6, the coma terms Z7 and Z8, and the spherical aberration term Z11, for patients with scleral lenses, even in the on-axis field of view, there will be astigmatism and coma terms caused by corneal irregularity and deformation, For off-axis rays, coma is a very obvious aberration for patients with keratoconus, and this example aims to demonstrate the targeted aberration modulation capability.

Figure 5. Comparison of Zernike coefficients before and after modulation of the central field of view under a 6mm pupil. The spherical surface is before modulation and the aspheric surface is after modulation.

Figure 6. Comparison of Zernike coefficients before and after 5-degree field of view modulation with a 6mm pupil. The spherical surface is before modulation and the aspheric surface is after modulation.

Figure 7 Comparison of Zernike coefficients before and after 10-degree field of view modulation with a 6mm pupil, the spherical surface is before modulation and the aspheric surface is after modulation.

The basic parameters of the individualized human eye were obtained by the corneal topograph test, and the human eye model was established. The anterior surface of the cornea was fitted with the spherical average curvature radius. After ray tracing, the aberration distribution in different fields of view was obtained. In order to facilitate comparison, a 6mm pupil is uniformly used. At this time, the difference between human eye aberrations is obvious. Aspheric surface refers to the average curvature radius of the anterior surface of the human cornea obtained by using corneal topography. Zernike polynomial expansion to get the final face distribution model, after ray tracing and modulation compensation. The Zernike aberration values are obtained, and the aberration distributions of different fields of view before and after modulation are shown in Figures 5-7. It can be clearly seen that the aberrations have been significantly reduced before and after modulation, reaching the phase purpose of modulation.

Figure 8-Figure 10 are the comparison charts of MTF before and after modulation of 0 degree field of view, 5 degree field of view, and -5 degree field of view under a 6mm pupil. It can be seen that due to the obvious reduction of aberration, the corresponding The modulation transfer function (MTF) has also been significantly improved.

Since the phase modulation function can be directly superimposed on the optical area of the front surface of the scleral lens, it is convenient for later lathe processing and molding. This phase modulation technology can specifically modulate and compensate the actual detected human eye aberration, It has wider adaptability and universality.

Specific examples are used herein to describe the inventive concept in detail, and the descriptions of the above embodiments are only used to help understand the core idea of the present invention. It should be pointed out that for those skilled in the art, any obvious modifications, equivalent replacements or other improvements made without departing from the inventive concept should be included within the protection scope of the present invention.

Claims (10)

1. A scleral contact lens based on phase modulation technology, characterized in that, the inner surface of the scleral contact lens, that is, the surface in contact with the cornea, is generally divided into three parts from the middle to the outside: the middle optical zone, the transition The transition zone connects the optic zone and the landing zone and is located at the limbus of the cornea, divided into two regions: the limbal adaptation zone and the cornea The limbal area is located at the edge of the cornea and maintains a gap with the edge of the cornea. The edge adaptation area is used to adjust the sagittal height of the scleral lens and to compensate for the sagittal height; It is in tangential contact with the sclera, so that the scleral contact lens can be well fixed on the sclera, and the landing zone forms an angle with the cornea, which is conducive to the exchange of tears. 2. A scleral contact lens based on phase modulation technology according to claim 1, characterized in that, the front surface optical zone of the scleral contact lens and the inner surface optical zone of the scleral lens jointly provide optical imaging characteristics, and the front surface optical zone has an optical imaging characteristic. A base shape similar to a standard facet shape (planar, spherical, quadric) plus an additional phase term defined by the Zernike standard coefficients that deflects the ray as it passes through the facet This surface type actually adds phase modulation to the standard surface type. The additional phase of the surface is defined as:

Here, N is the number of Zernike coefficients in the series, A _i is the coefficient in the Zernike polynomial, ρ is the normalized radial ray coordinate value, ψ is the angular coordinate value of the ray, D is the diffraction order, The phase function describes that on the basis of the standard surface, by increasing the modulation phase at any radial wavelength position, it plays a role in modulating the wavefront. A _i is the unit of wavelength, λ corresponds to the phase shift of 2π,

is the wavefront distribution in the polar coordinate system. 3 . The scleral contact lens based on phase modulation technology according to claim 2 , wherein the standard face shape (basal shape) of the optical zone of the front surface of the scleral contact lens adopts biquadratic with high-order terms. 4 . The surface design is expressed by the following formula:

in,

In addition to the base radius, the high-order coefficients of the conic coefficient can be different in the X and Y directions. α _i and β _i are the high-order aspheric coefficients in the x and y directions, respectively. The biquad surface allows to directly specify Rx, Ry , Kx and Ky. 4. A scleral contact lens based on phase modulation technology according to claim 3, wherein the surface shape of the front surface optical zone of the scleral contact lens, that is, the surface shape distribution after phase modulation is:

The first term is the basal surface profile, which together with the posterior surface of the scleral lens provides the power of the scleral contact lens, the next two are the high-order aspheric coefficients in the x and y directions, and the last term is superimposed on the basal surface. phase modulation term above. 5. A kind of scleral contact lens based on phase modulation technology according to claim 4, it is characterized in that, the face shape distribution of human cornea is measured with a corneal topograph, to obtain the sagittal height distribution map of the face shape of the front surface of the cornea, The equivalent radius of curvature and conic coefficient are fitted, and the difference in sag is expanded with the Zernike sag coefficient:

where k is the conic coefficient of the best-fit surface of the anterior corneal surface, c is the reciprocal of the radius of curvature, N is the Zernike number, B _i is the Zernike coefficient value, and ρ is the normalized radial ray coordinate value, ψ is the angular coordinate value of the ray. 6. A kind of scleral contact lens based on phase modulation technology according to claim 5, is characterized in that, the surface shape of the discrete sampling of the front surface of the cornea is directly converted into the phase surface, and the conversion mode is as follows:

The sag distribution of the anterior corneal surface is discretized on the two-dimensional xy plane, Δy is the sag of the anterior corneal sag at the Δx displacement interval, and the phase of the sag distribution can be directly transformed. 7 . The scleral contact lens based on phase modulation technology according to claim 6 , wherein, after the scleral contact lens is simulated wearing, an imaging optical system of the human eye after wearing the lens is established, and a ray tracing method is used to calculate the axis. 8 . When the upper field of view and the off-axis field of view are incident, the distribution of retinal defocus is based on the weighted sum of the RMS values of multiple fields of view at the retinal position as the evaluation function. The smaller the value, the better the imaging quality, namely:

where: S _i is the weighting coefficient, RMS _i is the RMS value of the speckle in the i field of view, and T is the total number of fields of view involved in the calculation. 8 . The scleral contact lens based on phase modulation technology according to claim 7 , wherein plasma treatment is adopted as a whole to improve the surface hydrophilicity, making it more comfortable to wear, and the plasma power is 10-2000W. 9 . 9. A scleral contact lens based on phase modulation technology according to claim 8, characterized in that, its refractive index range is between 1.4-1.6, and its oxygen permeability coefficient is (80-200)* ^10-11 (cm ² /s) [mlO ₂ /(ml×mmHg)]. 10 . The scleral contact lens based on the phase modulation technology according to claim 9 , wherein the total diameter thereof ranges from 12.5mm to 24mm, and the radius of curvature of the rear surface ranges from 6.4mm to 9.2mm. 11 .

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