RU2314079C1 - Surgical correction method for treating presbiopia cases aggravated with simple 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 concave cylindrical surface arranged within the whole optical zone. When forming it, central internal segment to be withdrawn is traced. Central internal segment symmetry center is made coincide with the optical zone center, and central internal segment symmetry axis is made coincide with the weak 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. The transition zone surface is coupled with its internal edge to external edge of the first optical surface and with its external edge to cornea portion that is not to be subjected to treatment. 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EFFECT: improved visual function in long and short distance; reduced luminous halation; minimized volume of withdrawn eye tissues.

15 dwg

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 with refractive errors" according to patent RU No. 2197209, A61F, 9101 priority from 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 required by the patient for professional work near, and the degree of planned anisometropia to create weak myopia in the paired eye are additionally 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 from 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 simple 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 simple myopic astigmatism, including the effect of excimer laser radiation on the cornea of the eye, optical surfaces and surfaces of the transition zone (PZ) are formed by sequential layer-by-layer removal of cornea sections, the first cylindrical concave is initially formed an optical surface lying within the entire optical zone (OZ), by forming a zone in the form of an inner central segment (B CA), formed by two parallel chords to be removed, and two symmetric external segments that cannot be removed, while the center of symmetry of the HVC is aligned with the center of the optical zone, the axis of symmetry of the HVC lying parallel to the chords of the HVC is combined with the weak axis of astigmatism, with each subsequent by layer-by-layer exposure, the area of the CCV is increased until the distance between the chords is equal to the diameter of the zone of influence; 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 the Central circular zone, not subject to removal, and increase the area of the Central zone with each removed layer; then form the surface of the transition zone (PPZ) within the area of the exposure zone (SV), lying in the range from 0.04 to 0.2 of the diameter of the SV 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 corneal area, not subject to 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, and this surface is formed by circles to be removed, with a center 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 simple 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 - 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 (FIG. 2).

Figure 2 presents:

The first optical surface 5;

The 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 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 the chords 13 is equal to the diameter of the impact zone 10. In FIG. 5, two symmetrical outer segments 14 that cannot be removed. not shaded, and the VCC 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 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 (Figure 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 18 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 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 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.

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

The proposed method is characterized by the following clinical examples.

Example 1: Patient T., 66 years old. Condition before surgery:

Far visual acuity: Vis OD = 0.2 cyl-1.75 D ax 0 ° = 1.0

Near visual acuity: Vis OD = 0.3 sph + 1.25 D cyl + 1.75 D ax 90 ° = 1.0

Corneal curvature: 44.5 D - 0 °, 42.75 D - 90 °, average - 43.6 D.

Corneal thickness: 516 microns.

Diagnosis: Simple mild myopic astigmatism, presbyopia.

The operation LASIK in accordance with the proposed invention.

Condition after surgery:

Distance Visual Acuity: Vis OD = 1.0

Near visual acuity: Vis OD = 0.8 sph + 0.5 D = 1.0

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

Example 2: Patient N., 60 years old.

Condition before surgery:

Visual acuity in the distance: Vis OD = 0.3 cyl-1,5 D ax 0 ° = 1,0

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

Corneal curvature: 43.0 D - 0 °, 41.5 D - 90 °, average - 42.25 D.

Corneal thickness: 525 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

Visual acuity in the vicinity: Vis OD = 0.7 sph + 0.75 D = 1.0

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

Example 3: Patient P., 51 years old. Condition before surgery:

Distance Visual Acuity: Vis OD = 0.4cyl-1.5 D ax 0 ° = 1.0

Near visual acuity: Vis OD = 0.4 cyl + 1.5 D ax 90 ° = 1.0

Corneal curvature: 42.5 D - 0 °, 41.0 D - 90 °, average - 41.75 D.

Corneal thickness: 532 microns.

Diagnosis: Simple mild myopic astigmatism, presbyopia.

The operation LASIK in accordance with the proposed invention.

Condition after surgery:

Distance Visual Acuity: Vis OD = 1.0

Near visual acuity: Vis OD = 1.0

Corneal curvature: 40.75 D - 0 °, 40.75 D - 90 °, average - 40.75 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 implementing a spatial effect on the cornea of the eye by simultaneously combining the methods 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, provides 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 simple 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 simple 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, initially forming the first cylindrical concave optical surface lying throughout optical zone (OZ), by forming a zone in the form of an internal central segment (VCC), formed by two parallel chords and a circle with the radius of the zone of influence to be removed, and two symmetric external segments that cannot be removed, while the center of symmetry of the HVC is combined with the center of the optical zone, the axis of symmetry of the HVC lying parallel to the chords of the HVC is combined with a weak axis of astigmatism, with each by subsequent layer-by-layer exposure, the area of the CCS is increased until the distance between the chords is equal to the diameter of the zone of influence, then a second optical surface is formed, the optical axis of which coincides with the center 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 in the center of the optical zone containing a central circular zone which 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 range from 0.04 to 0.2 of the diameter of the impact zone connected by the inner edge of the PPZ with an external the edge of the first optical surface, and the outer edge of the PPZ with the corneal portion not to be affected, in the form of a part of the convex outer surface (CVP) of the annular toroid formed by the rotation of the circular arc around the optical axis without intersecting this axis, while the arc rests on the chord located under angle to the optical axis and lying with the optical axis in the same plane, this surface being formed by circular zones to be removed, centered at 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 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 laser spot diameter of 0.5-1.5 mm, and pulse durations of 5-8 ns , pulse repetition rate from 30 to 500 Hz.

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