RU2514840C1 - Method for surgical correction of presbyopy combined with simple myopic astigmatism with preserving corneal surface asphericity - Google Patents

Abstract

FIELD: medicine.

SUBSTANCE: eye cornea is exposed to an eximer laser light at wave length 193-222 nm, pulse energy 0.8-2.1 mJ, laser spot diameter 0.5-1.5 mm, pulse length 5-8 nm, pulse repetition frequency 30 to 500 Hz. This exposure aiming at a sequential corneal abrasion is combined with forming optical surfaces and transition surfaces. A first cylindrical convex optical surface is formed within the entire optical cornea (OC). When forming the same, an ablated inner central segment (ICS) is marked. The centre of ICS symmetry matches with the OC centre. An axis of ICS symmetry matches with a weak axis of astigmatism. A second optical surface is formed as a convex ellipsoid of rotation with a negative conic constant within -0.1 to -0.4. An optical axis of the second optical surface matches with the OC centre. A diameter of the second optical surface is related to an OC diameter as a value within the range of 0.85 to 0.95. Then, the transitions surfaces (TS) are formed as a convex outer surface of an O-toroid. The transition surface is formed so that its inner border is coupled with an outer border of the first optical surface, and its outer border - with an intact cornea. A TS width makes 0.04 to 0.2 diameters of the exposure.

EFFECT: method enables minimising the amount of the resected eye tissue, provides the high far and near visual functions with no additional spectacle correction with a decreased light cap.

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Description

The invention relates to ophthalmology and can be used in the correction of presbyopia in combination with simple myopic astigmatism. The problem of presbyopia correction in combination with simple myopic astigmatism is one of the urgent in ophthalmology. Presbyopia is a visual impairment due to old age, is a consequence of the loss of the elastic properties of the lens, which causes a decrease in accommodation and visual impairment near. About 7% of all presbyopes suffer from presbyopia in combination with simple myopic astigmatism. All this makes the problem of presbyopia correction in combination with simple myopic astigmatism one of the urgent problems of ophthalmology.

The well-known "Method of surgical correction of presbyopia in combination with simple myopic astigmatism" according to patent RU No. 2314079, A61F, 9101 priority from 04.25.2006

The method of surgical correction of presbyopia in combination with simple myopic astigmatism involves the action of radiation of an excimer laser on the cornea of the eye with the formation of optical surfaces and the surface of the transition zone (PZ) in several stages by layer-by-layer removal of cornea.

The first optical surface has the form of a concave cylindrical surface centered in the center of the optical zone (OZ). The second optical surface has the form of a convex spherical surface, its diameter is 0.28-0.55 diameter of the OZ, and its optical axis coincides with the center of the OZ. The first surface of the PPZ is formed as part of the convex outer surface of the first annular toroid with a width of 0.04-0.2 diameter of the impact zone. The outer edge of the first PPA is mated with a section of the cornea that is not subject to exposure. The second PPZ is formed as part of the concave inner surface of the second annular toroid of the same width. The inner edge of the second PPZ mate with the outer edge of the first optical surface, and the outer edge with the inner edge of the first PPZ.

However, this method has some drawbacks: the presence of a significant light halo of spherical aberration, as well as the restoration of visual acuity for more than close.

The objective of the invention is to develop a method for surgical correction of presbyopia in combination with simple myopic astigmatism in order to ensure high visual functions in the distance and near, as well as to reduce the light halo and minimize spherical aberration.

The technical result achieved by the invention is to reduce the halo of light, minimize spherical aberration, and also restore vision for both far and near.

The specified technical result is achieved by the fact that in the method of surgical correction of presbyopia in combination with simple myopic astigmatism while maintaining the asphericity of the corneal surface, including exposure to excimer laser radiation with a wavelength of 193-222 nm, pulse energy of 0.8-2.1 mJ, diameter a laser spot of 0.5-1.5 mm, a pulse duration of 5-8 ns, a pulse repetition rate of 30 to 500 Hz on the cornea of the eye with the formation of two optical surfaces: the first cylindrical concave optical surface lying in within the entire optical zone (OZ), form by forming a zone in the form of an inner central segment (HSC) formed by two parallel chords to be removed and two symmetric external segments not to be removed, while the center of symmetry of the HCC is combined with the center of the optical zone, the axis of symmetry of the VCC, lying parallel to the chords of the VCC, combine with the weak axis of astigmatism; then form a second optical surface, the optical axis of which coincides with the center of the optical zone; after that, the surfaces of the transition zone are formed: the first surface of the transition zone (PPZ) conjugated by the outer edge with a portion of the cornea not subject to impact is formed as part of the convex outer surface (CVP) of the first annular toroid; the second PPZ, conjugated by the inner edge with the outer edge of the first optical surface, and the outer edge with the inner edge of the first PPZ, is formed as part of the concave inner surface (CVP) of the second annular toroid; according to the invention, the second optical surface is formed in the form of a convex ellipsoid of revolution with a negative conical constant from -0.10 to -0.4, and the ratio of the diameter of the second optical surface to the diameter of the SC lies in the range from 0.85 to 0.95 of the diameter of the SC.

The decrease in the halo of light occurs due to the fact that the second optical surface has the form of a convex ellipsoid of revolution and the ratio of its diameter to the diameter of the SC lies in the range of 0.85 to 0.95 of the diameter of the SC; restoration of vision both far and near is provided by the formation of two optical surfaces, the second of which is in the form of an ellipsoid, minimization of spherical aberration is achieved by the fact that the surface of the second optical zone has a negative conical constant from -0.1 to -0.4.

The set of essential distinguishing features proposed by the authors is necessary and sufficient for an unambiguous positive solution of the technical problem posed: creating a method for surgical correction of presbyopia in combination with simple myopic astigmatism in order to ensure high visual functions in the distance and near without additional spectacle correction, reducing the light halo, while minimizing spherical aberration.

The invention is illustrated by drawings Fig.1-15. They show:

Figure 1 is a frontal section of a radiation exposure zone;

Figure 2 is a frontal section of the location of the optical and transition zones, reduced to a plane;

Figure 3 is a top view of the corneal exposure zone;

Figure 4 - surface formation 5;

5 is an increase in the area of the inner segment 12;

6 is a structure of a second optical surface 6;

Fig.7 - the formation of the second optical surface;

Fig - increase the area of the circular zone 19;

Fig.9 - the formation of the surface 8 of the transition zone;

Figure 10 is a top view of the surface 8;

11 is an isometric view of the surface 8;

Fig - frontal section of the surface 8;

Fig - the formation of a circular zone 24;

Fig - reduction of the circular zone 25;

Fig - further reduction of the circular zone 26.

The method proposed by the authors is as follows.

The method consists in exposing an excimer laser 1 to the cornea of the eye 2 by sequential layer-by-layer removal of sections 3 (FIG. 1) of the cornea 2. On the cornea 2, sections 4 that cannot be removed are formed (Figure 2).

Figure 2 presents:

The first optical surface 5;

The second optical surface 6;

Optical zone 7;

Surface 8 of the transition zone;

Transitional Zone 9.

In figure 2, the dots show the boundaries of the surfaces 5, 6, 8, 4.

By a part of the surface of the cornea 2 to be removed is meant a portion of the cornea of a certain shape that is exposed to laser radiation 1 and removed as a result of this effect.

By a part of the surface of the cornea that cannot be removed is meant a portion of the cornea of a certain shape that is not exposed to laser radiation and cannot be removed.

By optical surface is meant the interface between two media with different refractive indices, which serves to change the path of the rays when creating a high-quality optical image on the retina of the eye.

By a layer of the cornea is meant a portion of the cornea, the shape of which changes upon a single exposure to a spatially ordered series of laser radiation pulses.

A top view of the exposure zone is shown in FIG. 3.

Surfaces 5, 6, 8 are shown in FIGS. 2, 3.

By the optical zone 7 is meant the zone in which the optical surfaces 5, 6 are formed (FIG. 3).

The impact zone 10 refers to the zone in which the optical surfaces and the surface of the transition zone are formed.

The optical axis 11 is the axis of symmetry of all formed optical surfaces and the surfaces of the transition zones (Fig.2, 3).

The optical surfaces 5, 6 and the surface of the transition zone 8 are formed by sequential layer-by-layer removal of corneal patches. There are also sections 4 of the cornea 2, not to be removed, located on the periphery of the cornea.

The implementation of the method should be divided into several stages.

Initially, a first cylindrical concave optical surface 5 is formed that lies within the entire optical zone 7 by forming an inner central segment 12 (VCC) bounded by two parallel chords 13 and a circle with a radius of the impact zone 10 to be removed and two symmetric outer segments 14, not subject to removal (Figure 4). Mark the VCC to be removed (Figure 4).

The center of symmetry of the HVC is combined with the center 11 of the optical zone 8, the longitudinal axis 15 of the HVC is combined with the weak axis of astigmatism 16 (Figure 4).

4, for convenience of presentation, the case is shown where the weak axis 16 is horizontal and the strong axis 17 of astigmatism is vertical. In practice, cases with a different arrangement of the axes of astigmatism are possible (not shown in the figure).

With each subsequent layer-by-layer exposure, the area of the HCV 12 is increased (Figure 5). It increases until the distance between chords 13 is equal to the diameter of the impact zone 10. In FIG. 5, two symmetric outer segments 14 that cannot be removed are not shaded, and the HVC is shaded. The spatial totality of all the VCC of the cornea to be removed, in which the area of the subsequent VVC is larger than the area of the previous VVC, creates a concave cylindrical optical surface 5, which allows to obtain high visual functions with distance vision.

Then, a second optical surface 6 is formed, the optical axis of which coincides with the center of the optical zone, the ratio of the diameter of the second optical surface to the diameter of the SC lies in the range from 0.85 to 0.95 of the diameter of the SC, in the form of a convex ellipsoid of revolution with a negative conical constant from -0 , 1 to −0.4 (FIG. 6). The surface 6 includes the center 11 of the optical zone 7.

The surface 6 is obtained by forming concentric rings 18 with a center in the center 11 of the optical zone, bounded by a circle with a radius of the impact zone 10, containing a circular central zone 19, not to be removed (Fig.7). In FIG. 7, zone 19 is not shaded, and the concentric ring 15 is shaded.

Zone 19 during laser irradiation is not removed during the formation of the first corneal layer that changes in shape and each of the subsequent corneal layers that are required to create a surface 6.

With each removed layer, an increase in the area of the central zone 19 and a reduction in the area of zone 18 is performed (Fig. 8). The spatial combination of all circular layers of the cornea that cannot be removed, in which the diameter of the subsequent layer of the cornea is larger than the diameter of the previous one, creates an optical surface in the form of a convex ellipsoid of revolution. Surface 6 allows you to get high visual functions with near vision.

Then form the surface 8 of the transition zone, which is the surface of the annular toroid. An annular toroid means a surface formed by the rotation of a circle around an optical axis without intersecting this axis. In the present invention, the surfaces 8 are part of a circular toroid and are formed as part of the convex external (CVP) surface of the annular toroid (Figure 9). The surface 8 is formed by rotating a flat segment 21, convex towards the optical axis, around the axis 11 of the surface 8 without intersecting the axis 11. The arc of the circle 21 of the segment 20 is based on the chord 22 located at an angle 23 to the axis 11 and lying with the axis 11 in the same plane (Fig.9). Top view of surface 8 in FIG. 10. The surface 8 in isometric projection is shown in Fig.11.

The surface 8 is formed by forming circular zones 24 to be removed, bounded by a circle with a radius of the impact zone 10, with a center of 11, in the range from 0.04 to 0.2 of the diameter of the impact zone.

A frontal section of the surface 8, explaining the formation of the circular zones 24, is shown in FIG. 12. Subsequently, in each layer, the area of the circular zone 24 to be removed is reduced in layers. Positions 25, 26 show a decrease in the circular zone 20. FIGS. 13, 14, 15 show a layered decrease in the area of the circular zones 24, 25, 26 (shaded in the figures).

The outer edge of the surface of the transition zone 8 is mated with the portion of the cornea 4, not subject to laser exposure, and the inner edge of the surface of the transition zone 8 is combined with the outer edge of the optical surface 5.

Excimer laser action on the cornea is carried out with the following parameters: excimer laser radiation wavelength of 193-222 nanometers, pulse energy 0.8-2.1 millijoules, laser spot diameter 0.5-1.5 mm, 1 pulse duration 5-8 nanoseconds, pulse repetition rate from 30 to 500 hertz.

The proposed method is characterized by the following clinical examples.

Example 1: Patient B., 54 years old.

Condition before surgery:

Visual acuity in the distance: Vis OD = 0.5 cyl-1,0 D ax 10 ° = 1,0.

Near visual acuity: Vis OD = 0.4 sph + 1.25 D cyl-1.0 D ax 10 ° = 1.0.

Corneal curvature: 44.5 D - 10 °, 42.5 D - 100 °, average - 43.5 D.

Corneal thickness: 556 microns.

Diagnosis: Simple mild myopic astigmatism, presbyopia.

The operation LASIK in accordance with the proposed invention.

Condition after surgery:

Visual acuity in the distance: Vis OD = 1.0.

Near visual acuity: Vis OD = 0.9 sph + 0.25 D = 1.0.

Corneal curvature: 43.0 D - 10 °, 43.0 D - 100 °, average - 43.0 D.

Example 2: Patient E., 51 years old.

Condition before surgery:

Visual acuity in the distance: Vis OD = 0.5 cyl-2.0 D ax 0 ° = 1.0.

Near visual acuity: Vis OD = 0.6 sph + 1.0 D cyl-2.0 D ax 0 ° = 1.0.

Corneal curvature: 43.0 D - 0 °, 41.0 D - 90 °, average - 42.0 D.

Corneal thickness: 544 microns.

Diagnosis: Simple mild myopic astigmatism, presbyopia.

The operation LASIK in accordance with the proposed invention.

Condition after surgery:

Visual acuity in the distance: Vis OD = 0.8 cyl-0.5D ax 0 ° = 1.0.

Visual acuity in the vicinity: Vis OD = 0.7 sph + 0.25 D -0.5 ax 0 ° = 1.0.

Corneal curvature: 41.0 D - 0 °, 41.0 D - 90 °, average - 41.0 D.

Example 3: Patient K., 55 years old.

Condition before surgery:

Visual acuity in the distance: Vis OD = 0.3 cyl-4.0 D ax 40 ° = 0.7.

Near visual acuity: Vis OD = 0.3 sph + 0.5 cyl-4.0 D ax 40 ° = 0.7.

Corneal curvature: 45.0 D - 40 °, 41.0 D - 130 °, average - 43.0 D.

Corneal thickness: 547 microns.

Diagnosis: Simple moderate myopic astigmatism, presbyopia.

The operation LASIK in accordance with the proposed invention.

Condition after surgery:

Visual acuity in the distance: Vis OD = 0.8 cyl-0.75 D ax 40 ° = 1.0.

Near visual acuity: Vis OD = 0.9.

Corneal curvature: 42.0 D - 40 °, 41.0 D - 130 °, average - 41.5 D.

The presence of surfaces 5, 6 provides high visual functions with near and far vision.

Features of the second optical surface: its shape in the form of a convex ellipsoid of revolution and a sufficiently wide diameter from 0.85 to 0.95 of diameter 03; reduce the effect of a circular halo.

Parameters of the conical constant from -0.1 to -0.4 of the second optical surface allow minimizing spherical aberration.

The whole set of essential distinguishing features of the invention indicated in the claims, including radiation parameters, provide an unambiguous positive solution to the claimed technical problem.

The use of the invention in the FSBI MNTK "Eye Microsurgery" them. Acad. S.N. Fedorova made it possible to confirm an unambiguous positive solution to the stated technical problem, the development of a method for surgical correction of presbyopia combined with simple myopic astigmatism to ensure high visual functions in the distance and near without additional spectacle correction, while minimizing spherical aberration.

Claims (1)

A method of surgical correction of presbyopia in combination with simple myopic astigmatism, including exposure to excimer laser radiation with a wavelength of 193-222 nm, pulse energy of 0.8-2.1 mJ, laser spot diameter of 0.5-1.5 mm, pulse duration 5-8 ns, the pulse repetition rate from 30 to 500 Hz on the cornea of the eye with the formation of two optical surfaces: the first optical surface lying within the entire optical zone (OZ) is formed in the form of a concave cylindrical surface by forming a zone in the form of an internal ENTRAL segment (DSV) formed by two parallel chords to be deleted, and two symmetrical outer segments are not to be removed, with the center of symmetry of the DSV is aligned with the optical zone center axis of symmetry DSV lying parallel chords DSV aligned with astigmatism weak axis; then form a second optical surface, the optical axis of which coincides with the center of the optical zone; after that, the surfaces of the transition zone are formed: the first surface of the transition zone (PPZ), conjugated by the outer edge with a portion of the cornea not subject to impact, is formed as part of the convex outer surface (CVP) of the first annular toroid; the second PPZ, conjugated by the inner edge with the outer edge of the first optical surface, and the outer edge with the inner edge of the first PPZ, is formed as part of the concave inner surface (CVP) of the second annular toroid; characterized in that the second optical surface is formed in the form of a convex ellipsoid of revolution with a negative conical constant from -0.1 to -0.4, while the ratio of the diameter of the second optical surface to the diameter of the SC lies in the range from 0.85 to 0.95 of the diameter OZ.

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