RU2314080C1 - Surgical correction method for treating presbiopia cases aggravated with complex myopic astigmatism - Google Patents

Abstract

FIELD: medicine.

SUBSTANCE: method involves treating eye cornea with excimer laser radiation with optical surfaces and transition zone surface being formed by sequentially layer-by-layer removing cornea segments. Action parameters are wavelength of 193-222 nm pulse power of 0.8-2.1 mJ, laser spot diameter of 0.5-1.5 mm, pulse duration of 5-8 ns, frequency of 30-500 Hz. The first optical surface is elliptical concave one arranged within the whole optical zone. When forming it, central elliptical zone that is not to be withdrawn, is traced. Central elliptical zone symmetry center is made coincide with the optical zone center, major axis of the central elliptical zone is aligned with the weak astigmatism axis and the minor axis of the central elliptical zone with the strong astigmatism axis. The second optical surface is formed as spherical convex surface which optical axis coincides with the optical zone center. The second optical surface diameter is 0.28-0.55 times as large as the optical zone diameter. The transition zone surface is formed as a part of convex external surface of annular toroid. Internal transition zone surface edge is coupled with external edge of the first optical surface and external transition zone surface edge is coupled with cornea portion that is not to be withdrawn. Transition zone surface width is 0.04-0.2 times as large as action zone diameter.

EFFECT: improved visual function in long and short distance; reduced luminous halation; minimized volume of withdrawn eye tissues.

17 dwg

Description

The invention relates to ophthalmology and can be used in the correction of presbyopia in combination with complex myopic astigmatism. The problem of presbyopia correction in combination with complex 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. Complex myopic astigmatism is a combination of spherical myopia with simple myopic astigmatism. About 50% of all presbyopes suffer from presbyopia in combination with complex myopic astigmatism. All this makes the problem of presbyopia correction in combination with complex myopic astigmatism one of the urgent problems of ophthalmology:

The well-known "Method of surgical correction of presbyopia with refractive errors" according to patent RU No. 2197209, A61F 91/01 priority of 06/06/2000

A method for surgical correction of presbyopia with refractive errors, including exposure to an excimer laser first on the cornea of the leading eye until emmetropic refraction is achieved, and then on the cornea of the paired eye until mild myopia is achieved. Additionally, the relative accommodation margin, the positive part of the focal zone of the paired eye, the optimal distance necessary for the patient to work professionally close, are determined, and the degree of planned anisometropia to create weak myopia on the paired eye is determined by the formula

D = 1 / h-0.5 · [POS (A-Fpos) + POS ((Y-35) / 10 + 0.6)],

where h is the optimal distance required by the patient for professional activities near.

However, this method has significant disadvantages: it is not possible to achieve high visual functions while minimizing the amount of tissue removed by the eye, the presence of a significant light halo.

The technical result achieved by the invention is the development of a method for surgical correction of presbyopia in combination with complex myopic astigmatism in order to ensure high visual functions in the distance and near while minimizing the volume of removed eye tissue and reducing the light halo.

The specified technical result is solved by the fact that in the method of surgical correction of presbyopia in combination with complex myopic astigmatism, including the effect of radiation of an excimer laser on the cornea of the eye, the optical surfaces and the surfaces of the transition zone (PZ) are formed by sequential layer-by-layer removal of cornea sections, the first ellipsoidal concave is initially formed an optical surface lying within the entire optical zone (OZ), by forming a circular zone of influence not to be removed and mark the central elliptical zone (CEZ) to be removed, while the center of symmetry of the CEZ is combined with the center of the optical zone, the major axis of the CEZ is combined with the weak axis of astigmatism, and the small axis of the CEZ is combined with the strong axis of astigmatism, with each subsequent layering increase the area of the CEZ to be removed by forming a curved, closed figure, bounded by a circle with the radius of the impact zone and a curved line that is the outer part of the CEZ, further increase the area of the CEZ until p the main axis of the CEZ with the value of the diameter of the impact zone (SV), then they continue to form an optical surface by forming two symmetrical curved closed figures that cannot be removed, each of which is limited by an arc of a circle with the radius of the impact zone and a curved line that is the outer part of the CEZ; then a second optical surface 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 0.28 to 0.55 of the diameter of the SC, in the form of a convex spherical surface, by forming concentric rings to be removed, centered at the center of the optical zone containing a central circular zone that cannot be removed and increase the area of the central zone with each layer to be removed; then form the surface of the transition zone (PPZ) within the area of the impact zone (SV), lying in the range from 0.04 to 0.2 of diameter 3 V, connected by the inner edge of the PPZ with the outer edge of the first optical surface, and the outer edge of the PPZ with the cornea, not subject to exposure , in the form of a part of the convex outer surface (CVP) of the annular toroid formed by the rotation of the first flat segment of the circle around the optical axis without intersecting this axis, while the arc of the circle of this segment rests on a chord located at an angle to optical axis and lying with the optical axis in the same plane, this surface being formed by circles to be removed, centered in the center of the optical zone, the outer diameter of which decreases in layers; moreover, the effect on the surface of the cornea is produced by the radiation of an excimer laser with a wavelength of 193-222 nanometers, with an energy per pulse of 0.8-2.1 millijoules, with a laser spot diameter of 0.5-1.5 mm, a pulse duration of 5-8 nanoseconds, and a pulse repetition rate of 30 to 500 hertz .

The set of essential distinguishing features proposed by the authors is necessary and sufficient for an unambiguous positive solution of the technical problem posed: the creation of a method for surgical correction of presbyopia in combination with complex myopic astigmatism in order to ensure high visual functions in the distance and near without additional spectacle correction while minimizing the volume of removed eye tissue and light halo reduction.

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 - alignment of the axes of astigmatism;

5 is an increase in the area of the elliptical zone 14;

6 - equality of the major axis of the elliptical zone to the diameter of the impact zone;

7 is a view of curved closed figures 19;

Fig - the structure of the second optical surface 6;

Fig.9 - the formation of the second optical surface;

Figure 10 - increase in the area of the circular zone 12;

11 - education, surface 8 of the transition zone;

Fig - top view of the surface 8;

Fig is an isometric view of the surface 8;

Fig - frontal section of the surface 8;

Fig - the formation of a circular zone 26;

Fig - reduction of the circular zone;

Fig - reduction of the circular zone.

The method proposed by the authors is as follows.

The method consists in exposing the cornea of the eye 2 to radiation of the excimer laser 1 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;

second optical surface 6;

optical zone 7;

surface 8 of the transition zone;

transition 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 surfaces 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 ellipsoidal concave optical surface 5 is formed that lies within the entire optical zone 7 by forming a zone 12 that cannot be removed.

Mark the central elliptical zone 13 (CEZ) to be removed (Figure 4). In FIGS. 4-7, zone 12 is not shaded, and zone 13 is shaded.

The center of symmetry of the CEZ is combined with the center of the optical zone 7, the major axis 14 of the CEZ is combined with the weak axis of astigmatism 15, and the minor axis 16 of the CEZ is combined with the strong axis of astigmatism 17 (Figure 4).

Zone 13 during laser irradiation is removed during the formation of the first corneal layer of varying shape and each of the subsequent corneal layers of shape required to create the surface 5.

4, for convenience of presentation, shows the case when the weak axis 15 of astigmatism is horizontal and the strong axis 17 is vertical. In practice, cases with a different arrangement of the axes of astigmatism (not shown) are possible.

With each of the subsequent laser actions, the area of the CEZ 13 increases, and the zone 12 decreases. When this zone 12 forms a curved closed figure, bounded by a circle with the radius of the impact zone 10 and a curved line, which is the outer section of the CEZ 18. (Figure 5). With each subsequent layer-by-layer exposure, the area of the CEZ 13 to be removed is increased and the area of the curvilinear figure not to be removed is reduced (Figure 5).

The area of the CEZ to be removed is increased until the major axis 14 of the CEZ is equal to the diameter of the impact zone 10 (Figure 6). In this case, the curvilinear zone to be removed forms two symmetric curvilinear closed figures 19, each of which is bounded by an arc of a circle 10 with the radius of the zone of influence and a curved line 18, which is the outer part of the CEZ 13. In FIG. 6, two symmetrical closed figures 19 are not shaded.

The formation of the optical surface is continued by the formation of a CEZ 13 to be removed and two symmetrical curved closed figures 19 that cannot be removed. With each subsequent layer, the area of the CEZ 13 to be removed is increased, and the area of the curvilinear closed figures 19, not to be removed, is reduced (Fig.6, 7). Each of the curved closed figures 19 is limited by an arc of a circle 10 with the radius of the impact zone and a curved line 18, which is the outer section of the CEZ 13 (Fig.7). Surface 5 allows you to get high visual functions with distance vision.

Then form the second optical surface 6, 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 0.28 to 0.55 of the diameter of the SC, in the form of a convex spherical surface (Fig. 8). The surface 6 includes the center 11 of the optical zone 7.

The surface 6 is obtained by forming concentric rings 20 centered in the center 11 of the optical zone, bounded by a circle with the radius of the impact zone 10, containing a circular central zone 21 that cannot be removed (Fig. 9). 9, zone 21 is not shaded, and the concentric ring 20 is shaded.

Zone 22 during laser irradiation is not removed during the formation of the first corneal layer of varying shape and each of the subsequent corneal layers of shape required to create the surface 6.

With each removed layer, an increase in the area of the central zone 21 and a reduction in the area of zone 20 are performed (Figure 10). 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 a convex spherical optical surface. 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 surface 8 is part of a circular toroid and is formed as part of a convex outer (CVP) surface of the annular toroid (Figure 11). The surface 8 is formed by rotating a flat segment 22, convex towards the optical axis, around the axis 11 of surface 8 without intersecting axis 11. The arc of circle 23 of segment 22 is supported by a chord 24 located at an angle of 25 to axis 11 and lying with axis 11 in the same plane (Fig.11). Top view of the surface 8 in Fig.12. The surface 8 in isometric projection is shown in Fig.13.

The surface 8 is formed by forming circular zones 26 to be removed, bounded by a circle with a radius of the impact zone 10, with a center of 12, in the range from 0.04 to 0.2 of the diameter of the impact zone.

The frontal section of the surface 8, explaining the formation of circular zones 26, is shown in Fig. Subsequently, in each layer, the area of the circular zone 26 to be removed is reduced. Positions 27, 28 show a decrease in circular zones 26. Figs. 15, 16, 17 show a layer-by-layer decrease in the area of circular zones 26, 27, 28 (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.

The excimer laser effect on the cornea according to the invention 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, pulse duration 5-8 nanoseconds, pulse repetition rate 30 to 500 hertz.

The proposed method is characterized by the following clinical examples.

Example 1: Patient T., 62 years old.

Condition before surgery:

Visual acuity into the distance: Vis OS = 0.1 sph - 2.0 D cyl - 1.5 D ax 0 ° = 0.8

Near visual acuity: Vis OS = 0.2 sph - 0.5 D cyl + 1.5 D ax 90 ° = 0.8

Corneal curvature: 44.5 D - 0 °, 43.0 D - 90 °, average - 43.75 D.

Corneal thickness: 527 microns.

Diagnosis: Complicated weak myopic astigmatism, presbyopia. The operation LASIK in accordance with the proposed invention.

Condition after surgery:

Visual acuity in the distance: Vis OS = 0.6 sph - 0.5 D = 0.8

Near visual acuity: Vis OS = 0.8

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

Example 2: Patient K., 64 years old.

Condition before surgery:

Visual acuity in the distance: Vis OS = 0.1 sph - 1.5 D cyl - 1.75 D ax 0 ° = 0.9

Near visual acuity: Vis OS = 0.2 sph - 0.25 D cyl + 1.75 D ax 90 ° = 0.9

Corneal curvature: 44.0 D - 0 °, 42.25 D - 90 °, average - 43.2 D.

Corneal thickness: 541 microns.

Diagnosis: Complicated weak myopic astigmatism, presbyopia. The operation LASIK in accordance with the proposed invention. Condition after surgery:

Visual acuity in the distance: Vis OS = 0.5 sph - 0.75 D = 0.9

Near visual acuity: Vis OS = 0.9

Corneal curvature: 40.75 D - 0 °, 40.75 D - 90 °, average - 40.75 D.

Example 3: Patient C. 63 years. Condition before surgery:

Visual acuity in the distance: Vis OD = 0.1 sph - 1.0 D cyl - 1.5 D ax 0 ° = 1.0

Near visual acuity: Vis OD = 0.2 sph - 0.5 D cyl + 1.5 D ax 90 ° = 1.0

Corneal curvature: 45.0 D - 0 °, 43.5 D - 90 °, average - 44.25 D.

Corneal thickness: 524 microns.

Diagnosis: Complicated weak myopic astigmatism, presbyopia. The operation LASIK in accordance with the proposed invention.

Condition after surgery:

Visual acuity in the distance: Vis OD = 0.7 sph - 0.5 D = 1.0

Near visual acuity: Vis OD = 1.0

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

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

Due to the fact that the edges of the surface 5 form an angle with the surface 4, it is necessary to form a smooth transition between the optical surface 5 and the zone of the cornea 4. This role is played by the surface 8 of the transition zone 10, made in accordance with the claims. The implementation of this surface in this form allows you to form a smooth transition between surfaces 5 and 4 and to prevent the occurrence of the effect of a circular halo.

Minimization of the volume of removed tissue of the eye is achieved by the whole set of technological methods for performing spatial effects on the cornea of the eye by simultaneously combining the techniques of removing and not removing curved shapes in each layer of the cornea with each exposure and the logically necessary combination of these techniques in each subsequent layer to create each of the optical surfaces 5 , 6, the surface of the transition zone 8 and maintaining the integrity of the surface 4 on the periphery of the cornea.

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 Federal State Institution IRTC “Eye Microsurgery” named after 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 in combination with complex myopic astigmatism to ensure high visual functions in the distance and near without additional spectacle correction while minimizing the volume of removed eye tissue.

Claims (1)

The method of surgical correction of presbyopia in combination with complex myopic astigmatism, including the action of excimer laser radiation on the cornea of the eye, characterized in that the optical surfaces and the transition zone surfaces are formed by sequential layer-by-layer removal of corneal portions, the first ellipsoidal concave optical surface is initially formed that lies within the entire optical zone (OZ), by forming a circular zone of influence not to be removed, and mark the central ellie the zone of symmetry (CEZ) to be removed, while the center of symmetry of the CEZ is combined with the center of the optical zone, the major axis of the CEZ is combined with the weak axis of astigmatism, and the small axis of the CEZ is combined with the strong axis of astigmatism, with each subsequent layering, the area of the CEZ to be removed is increased , by forming a curved, closed figure, bounded by a circle with the radius of the impact zone and a curved line that is the outer part of the CEZ, further increase the area of the CEZ until the major axis of the CEZ are equal to the diameter of the impact zone (SV), then they continue to form the optical surface by forming two symmetrical curved closed figures that cannot be removed, each of which is limited by an arc of a circle with the radius of the impact zone and a curved line that is the outer part of the CEZ, then form the second optical surface, 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 0.28 to 0.55 of the diameter of the SC, in the form of a convex spherical surface, by forming concentric rings to be removed, with a center in the center of the optical zone containing a central circular zone that cannot be removed, and increase the area of the central zone with each layer to be removed, then form the surface of the transition zone (PPZ) lying in the interval from 0.04 to 0.2 of diameter 3V, connected by the inner edge of the PPZ with the outer edge of the first optical surface, and the outer edge of the PPZ with the portion of the cornea that is not subject to impact, in the form of a part of the convex outer surface (CVP) of the rings of the toroid formed by rotating an arc of a circle around the optical axis without intersecting this axis, the arc resting on a chord located at an angle to the optical axis and lying on the same plane with the optical axis, and this surface is formed by forming circular zones to be removed, with center in the center of the optical zone, the outer diameter of which decreases in layers, and the effect on the surface of the cornea is produced by the radiation of an excimer laser with a wavelength of 193-222 nm, with an energy per pulse of 0.8-2.1 mJ, with a diameter of l a nuclear spot of 0.5-1.5 mm, a pulse duration of 5-8 ns, a pulse repetition rate of 30 to 500 Hz.

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