RU2419402C2 - Method of treating refraction abnormalities by impact of ultraviolet radiation and device for its realisation - Google Patents

Abstract

FIELD: medicine.

SUBSTANCE: group of inventions relates to ophthalmology. Method includes performing local anesthesia, instillation of photomediator, irradiation by UV radiation of eye cornea. Cornea is irradiated by UV radiation, distributed in intensity proportionally to value of mechanical tensions in each zone of cornea in accordance with the map of mechanical tensions. Device includes case with located in it source of UV radiation, connected to it power unit, located on one optic axis with UV radiation source optic focusing elements and diaphragm. As diaphragm used is digital micromirror device, control unit of which realises function of alteration of intensity of eye cornea irradiation by UV radiation.

EFFECT: application of said group of inventions will allow increasing treatment efficiency due to taking into account local mechanical tensions, present in cornea, in treatment of refraction abnormalities.

9 cl, 6 dwg, 5 ex

Description

The invention relates to medicine, more specifically to ophthalmology and can be used to treat refractive errors, including myopia, hyperopia, astigmatism and keratoconus, exposure to ultraviolet (hereinafter - “UV”) radiation.

A known method and device for treating keratoconus with UV radiation, which exerts a full aperture on the cornea (Wollensak G., Spörl E., Seiler T. Treatment of keratoconus by collagen cross linking. Der Ophthalmologie: Zeitschrift der Deutschen Ophthalmologischen Gesellschaft, 2003 , Jan, 100 (1): pp. 44-49).

This does not allow to treat a number of refractive errors, since it only gives stabilization of the corneal ectasia process.

The use of a UV illuminator without taking into account the distribution of mechanical stresses in the cornea, irradiation of the cornea with a UV source with a full aperture, which provides uniform illumination of the entire area of the cornea, can cause photo-burn, which, combined with an insufficient thickness of the cornea, is less than the depth of UV radiation exposure, can lead to damage to endothelial cells with the development of complications in the form of corneal dystrophy. In some cases, this requires the use of special mixtures of riboflavin with dextran, which allow you to create a thickening of the cornea due to temporary edema. This accordingly reduces the effect of the corneal collagen crosslinking procedure itself.

The technical result achieved by the implementation of the invention is to increase the effectiveness of the treatment due to the fact that when treating refractive errors, local mechanical stresses existing in the cornea are taken into account.

The specified technical result is achieved by irradiating the cornea with UV radiation, distributed in intensity in proportion to the magnitude of the mechanical stresses in each area of the cornea in accordance with the map of mechanical stresses.

Before irradiation, you can, if necessary, change the radius of curvature of the cornea by attaching a flat contact lens to the cornea using a vacuum ring.

UV radiation is polarized if necessary, directing the plane of polarization with respect to the plane of polarization of the cornea at an angle of 1 to 180 degrees.

Additionally, the position of the pupil is monitored and, if necessary, the center of the projected image is shifted.

Irradiation is carried out using a device that includes a housing with a UV radiation source located in it, a power and control unit connected to it, located on the same optical axis as the UV radiation source (hereinafter referred to as the “optical axis"), optical focusing elements and a diaphragm. Digital micromirror device (hereinafter - “DMD”) acts as a diaphragm. The DMD control unit implements the function of changing the radiation intensity, in particular, in proportion to the magnitude of the mechanical stresses in each area of the cornea in accordance with the map of mechanical stresses.

To change the curvature of the cornea, the device contains a contact lens designed to be fixed on the cornea of the eye, mounted on the same optical axis as the diaphragm and UV radiation source

The device may include a polarizer designed to be placed on the optical axis, configured to set the plane of polarization of UV radiation relative to the plane of polarization of the cornea within 1-180 degrees. The polarizer can be made in the form of a liquid crystal matrix.

The device also contains a pupil position sensor, the output of which is connected to the control unit of the digital micromirror device to ensure the displacement of the center of the projected image.

A digital micromirror device (DMD) forms an image on the surface of the cornea, where the maximum energy of UV radiation corresponds to areas with maximum mechanical stresses of the cornea, and UV radiation captures the tissue due to the crosslinking process. A digital micromirror device, acting as a diaphragm, reduces the damaging effect on the cornea. The individual form of the image projected by the UV radiation beam generated by the digital micromirror device allows achieving the desired effect by increasing the corneal strength within the areas experiencing maximum mechanical stress. In this case, the bulk of the corneal tissue is not damaged by UV radiation. The polarizer allows you to use the light polarization effect of the cornea to adjust the depth of exposure to UV radiation, eliminating the possibility of damage to photosensitive endothelial cells, which reduces the risk of complications from exposure to UV radiation on the cornea while maintaining the therapeutic effect. A flat contact lens with a vacuum retainer allows you to project a UV beam without spherical distortion, which enhances the effect.

When UV radiation affects the stroma of the cornea, cross-linking of collagen molecules occurs, which increases the strength of the cornea and stabilizes its curvature at the required level. Photopolymerization is activated by non-toxic water-soluble photo-mediators, and their absorption of radiation at a depth should protect the deep tissues of the cornea, in particular endothelial cells, from damage. Riboflavin can be such a photo-mediator, and it is used in the implementation of this technology. The process of collagen crosslinking is called crosslinking and can occur at various levels of a complex collagen structure. Cross-linking results in additional cross-linking in the tropocollagen, which forms the primary structure of this protein, additional cross-linking between the primary collagen structures is also formed, and, finally, new bridges between the collagen microfibrils can form. All this leads to increased aggregation of corneal collagen, its compaction and hardening. The clinical effect is due to these changes in the biomechanical parameters of the cornea, which can stabilize the curvature of the cornea with refractive errors.

Using a contact lens fixed to the cornea by a vacuum ring, a flat surface that allows you to project an image of the UV beam without spherical distortion, in addition, in the flattened state in the corneal tissue, all internal mechanical stresses caused by intraocular pressure are compensated, and the process of cross-linking of collagen structures takes place to the maximum favorable mechanical conditions. The cornea is known to have the ability to polarize light. Accordingly, it transmits light differently polarized at different angles. The polarizer of the device according to the invention allows you to polarize the UV rays of the emitter, which makes it possible to adjust the exposure depth by changing the angle with respect to the plane of polarization of the cornea. This leads, respectively, to an increase in the absorption coefficient of radiation in the outer layers of the cornea, which also reduces the dose of UV radiation in the sensitive endothelial layer of the cornea and reduces the risk of postoperative dystrophic complications.

A method of treating refractive errors with UV radiation and a device for its implementation is illustrated by drawings, where:

figure 1 shows a keratotopogram reflecting the curvature of the cornea at all points;

figure 2 shows a map of the distribution of the thickness of the cornea;

figure 3 shows a map of the distribution of mechanical stresses;

figure 4 shows a block diagram of a device;

figure 5 shows a block diagram of a device with a contact lens;

6 is a block diagram of a device with a polarizer.

In the housing 1 of the device is a UV radiation source 2 with a wavelength of 350-380 nm and optical elements 3 of quartz glass. The UV radiation source is connected to the power supply and control unit 4, which provides power supply, regulation of power and operating time of the device. The diaphragm is located between the elements of the optical system 3 and is made in the form of a digital micromirror device 6. The DMD control unit provides changes in the irradiation intensity in proportion to the magnitude of the mechanical stresses in each area of the cornea 7 in accordance with the map of mechanical stresses.

For this, a keratotopographic map of corneal curvature, a map of corneal thickness and intraocular pressure are preliminarily obtained, and a map of mechanical stresses of the cornea is calculated and formed, which is stored in the DMD control unit.

Due to the presence of a large number of micromirrors, DMD is able to form any image with a very high resolution and high contrast. Micromirrors, deviating under the influence of a control signal, completely or partially reflect radiation to a surface located at a distance equal to the working segment of the optical system of the device, or are reflected towards the absorber and then a shadow is formed. In addition, acting as a kind of digital aperture, a digital micromirror device can, under the influence of a control signal, move an image within the aperture of the device’s optical system, thereby fulfilling the function of a tracking system necessary to control eye displacement during the procedure. In addition, the proposed device may have a polarizer 9, which can be both in the device body and on the surface of the cornea contact lens 8, i.e. outside of the device.

The method is as follows. The keratotopogram of the eye of Fig. 1, a map of the distribution of the thickness of the cornea of Fig. 2 is preliminarily taken, the intraocular pressure is measured, and the mechanical stress of the cornea at each point is calculated by the formula τ = RT / 2d, where τ is the corneal stress, R is the corneal curvature at each T - intraocular pressure, d - thickness of the cornea. Then form a map of the mechanical stress of the entire cornea of Fig.3. The mechanical stress card is inserted into the control unit of the digital micromirror device. Perform local anesthesia. In the eye instill 1% solution of riboflavin for 30 minutes every 2 minutes, one drop. They are mounted on the cornea and a flat contact lens is fixed using vacuum. Using a UV radiation source 2 with a wavelength of 350-380 nm and with a power of not more than 5 mW / cm ² and a focusing optical system 3, the image of the corneal mechanical stress map is projected onto the latter, where the most intense sections correspond to the maximum brightness of the UV beam during from 1 to 90 minutes. When working without a contact lens, a follow-up system shown in FIG. 5 is used to compensate for adjusting movements of the eyeball. The pupil position sensor, made, for example, in the form of a video camera 10, transmits the pupil image to the DMD control unit, which shifts the center of the projected image by the required distance after the moving pupil. If the amplitude of the displacement of the pupil exceeds the ability to move the card, the radiation source is turned off and emits a sound warning signal about the shutdown. As soon as the pupil again falls into the coverage area of the tracking system, the UV radiation source is automatically turned on and continues to radiate until the specified dose is reached.

To reduce the likelihood of damage to the endothelial layer of the cornea, a polarizer is placed in the optical channel of the device. Due to the intrinsic polarization of the cornea, this element increases the absorption coefficient of part of the fibers of the corneal tissue, reducing the penetrating power of UV radiation and thereby protecting endothelial cells sensitive to ultraviolet radiation located on the inner surface of the cornea.

For the treatment of refractive errors, we apply a variant of the method when local crosslinking is performed in the form of a central spot with myopia or a concentric ring on the periphery of the cornea with hyperopia. For this, the digital micromirror device generates the corresponding images on the surface of the cornea, flattened with a flat contact lens and a vacuum ring. For the correction of hyperopic astigmatism, elliptically elongated concentric figures are projected, and for the correction of myopic astigmatism, central ellipses.

Below are examples of specific implementation of the method.

Example 1. Patient Yu., 29 years old. The diagnosis of moderate myopia in both eyes.

Visual acuity before surgery: right eye - 0.01 sph -4.25 D = 1.0 left eye - 0.02 sph - 3.5 D = l, 0 Ophthalmometry data: right eye 44.0 D - 90 ° left eye 43.25 D - 180 °

Myopia has not progressed for the past nine years.

The operation according to the proposed method. Alternately, first on the right and then on the left eye after local anesthesia and instillation of 1% riboflavin for 30 minutes, a flat contact lens is fixed on the surface of the cornea using a vacuum ring and the UV beam image is focused in the form of a central spot with a diameter of 5 mm. The exposure was 30 minutes.

The day after the operation, the right eye is calm, the reaction is of zero degree, there is no pain, when viewed on a slit lamp, there are no signs of corneal damage.

Visual acuity of both eyes 1.0 without additional correction.

A follow-up examination after 1 year showed no regression of the refractive effect.

Example 2. Patient Z., 28 years old. The diagnosis of mild myopia in both eyes, complex myopic astigmatism of the right eye.

Visual acuity before surgery: right eye - 0.1 sph -2.0 D cyl -1.0 D ax 65 ° = 1.0 left eye - 0.1 sph -1.5 D = 1.0 Ophthalmometry data: right eye 45.0 D - 65 ° left eye 43.5 D -

The operation according to the proposed method. Alternately, on the right and left eye after local anesthesia and instillation of 1% riboflavin for 30 minutes, an elliptical central spot with a long axis perpendicular to the meridian of 65 degrees is focused on the surface of the cornea. The exposure was 30 minutes.

The day after the operation, the right eye is calm, the reaction is of zero degree, there is no pain, when viewed on a slit lamp, there are no signs of corneal damage. Visual acuity after surgery = 1.0. A follow-up examination after 1 year showed no regression of the refractive effect in the right eye, and the left eye was treated using the same technique.

Example 3. Patient S., 38 years old. The diagnosis of myopic astigmatism, keratoconus in both eyes.

Visual acuity before surgery: right eye - 0,01 sph - 0,5 D, cyl -4,0 D ax 75 ° left eye - 0.2 cyl -3.75 D ax 80 °

The last year marks a decline in vision.

The operation according to the proposed method. After instillation of 1% riboflavin for 30 minutes, a polarizer was placed in the optical channel of the device. A spot formed by the UV source was focused on the surface of the cornea of the right eye. The exposure was 30 minutes.

The day after the operation, the right eye is calm, the reaction is of zero degree, there is no pain, when viewed on a slit lamp, there are no signs of corneal damage. A follow-up examination after 1 year showed the absence of disease progression in the right eye.

Example 4. Patient F., 14 years old. The diagnosis of hyperopic astigmatism, anisometropia.

Visual acuity of the left eye 0.3 cyl + 3.0 ax 90 ° = 0.5

The operation according to the proposed method. After local anesthesia and a 20-minute instillation of 1% riboflavin in vacuum, a corneal flat contact lens was fixed. A concentric elliptically elongated ring is projected on the cornea with a minimum diameter of 3.0 mm and a maximum of 6 perpendicular to the 90 ° axis. The exposure was 30 minutes.

The next day, the eye is slightly irritated. Visual acuity of 0.5-0.6.

The effect is stable for 1 year.

Example 5. Patient K., 44 years old. Diagnosis: mild hyperopia of the right eye.

Visual acuity before surgery: right eye -0.1 sph +2.25 D = 1.0 left eye = 1.0 without correction Ophthalmometry data: right eye 41.0 D - 180 ° left eye 42.75 D - 90 °

The operation according to the proposed method. After instillation of 1% riboflavin for 30 minutes, a flat lens was mounted and fixed with a vacuum ring on the cornea of the right eye. A ring with an inner diameter of 5 mm formed by a UV source was focused on the surface of the cornea of the right eye. The exposure was 20 minutes.

The day after the operation, the right eye is calm, the reaction is of zero degree, there is no pain, when viewed on a slit lamp, there are no signs of corneal damage. Visual acuity of both eyes = 1.0. A follow-up examination after 1 year showed a stable effect.

Claims (9)

1. A method of treating refractive errors with UV radiation, including local anesthesia, instillation of a photo mediator, irradiating the cornea with UV radiation, characterized in that the cornea is irradiated with UV radiation distributed in intensity in proportion to the amount of mechanical stress in each area of the cornea in accordance with map of mechanical stresses. 2. The method according to claim 1, characterized in that before irradiating the cornea with UV radiation, the radius of curvature of the cornea is changed by fixing the contact lens on the cornea of the eye. 3. The method according to claim 1, characterized in that the UV radiation is polarized, directing the plane of polarization with respect to the plane of polarization of the cornea at an angle from 1 to 180 °. 4. The method according to any one of claims 1 to 3, characterized in that they track the position of the pupil and, if necessary, shift the center of the projected image. 5. A device for treating refractive errors with UV radiation, comprising a housing with a UV radiation source located therein, a power supply connected thereto, located on the same optical axis as a UV radiation source, optical focusing elements and a diaphragm, characterized in that as a diaphragm, a digital micromirror device is used, the control unit of which implements the function of changing the intensity of irradiation of the cornea of the eye with UV radiation. 6. The device according to claim 5, characterized in that it contains a contact lens intended for fixation on the cornea of the eye, mounted on the same optical axis with the diaphragm and a UV radiation source. 7. The device according to claim 6, characterized in that it contains a polarizer designed to be placed on the optical axis, configured to set the plane of polarization of UV radiation relative to the plane of polarization of the cornea in the range of 1-180 °. 8. The device according to claim 7, characterized in that the polarizer is made in the form of a liquid crystal matrix. 9. The device according to any one of paragraphs.5-8, characterized in that it contains a pupil position sensor, the output of which is connected to the control unit of a digital micromirror device to provide displacement of the projected image.

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