RU2526476C1 - Method of surgical correction of presbyopia in combination with simple hypermetropic astigmatism with preservation of cornea surface asphericity - Google Patents

Abstract

FIELD: medicine.

SUBSTANCE: eye cornea is exposed to eximer laser irradiation with a wavelength of 193-222 nm, energy in a pulse 0.8-2.1 mJ, a diameter of the laser spot of 0.5-1.5 mm, the pulse duration of 5-8 ns, the pulse repetition frequency of 30-500 Hz. Optic surfaces and surfaces of the transitional zone are formed under such an impact, which ensures the successive layer-by-layer removal of the cornea sections. The first ellipsoidal convex optic surface is formed within the entire optic zone (OZ) of the cornea. In the process of its formation a zone in the form of an internal central segment (ICS) is created, which is not subjected to ablation. The ICS is formed by two parallel chords and a circumference with a diameter of the impact zone (IZ). The centre of the ICS symmetry is superposed with the centre of the optic zone. The axis of the ICS symmetry, located parallel to the chords, is superposed with the strong axis of astigmatism. After that, the second optic surface in the form of a convex rotation ellipsoid with a negative conic constant from -0.1 to -0.4 is formed. A ratio of a diameter of the second optic surface to the OZ diameter is within the interval from 0.85 to 0.95 of the OZ diameter. After that, transitional zone surfaces (TZS) are formed. The first TZS is formed in the form of a part of the convex external surface of the first circular toroid. The first TZS is formed in such a way that its external edge is conjugated with the section of the cornea which is not subjected to an impact. The second TZS is formed in the form of a part of the convex internal surface of the second circular toroid. The internal edge of the second TZS must be conjugated with the external edge of the first optic surface and the external edge - with the internal edge of the first TZS.

EFFECT: method makes it possible to minimise the volume of ablated tissue of the eye, ensures high visual functions at far and close distance without additional correction by means of glasses, and reduction of the light halo.

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Description

The invention relates to ophthalmology and can be used in the correction of presbyopia in combination with simple hyperopic astigmatism. The problem of presbyopia correction in combination with simple hyperopic 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 12% of all presbyopes suffer from presbyopia in combination with simple hyperopic astigmatism. All this makes the problem of presbyopia correction in combination with simple hyperopic astigmatism one of the urgent problems of ophthalmology.

The well-known "Method of surgical correction of presbyopia in combination with simple hyperopic astigmatism" according to patent RU No. 2306913, A61F, 9/01, priority from 04.25.2011.

The method of surgical correction of presbyopia in combination with simple hyperopic astigmatism involves the action of excimer laser radiation 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 convex 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, 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 hyperopic astigmatism in order to ensure high visual functions in the distance and near, as well as reduce the light halo and minimize spherical aberration.

The technical result achieved by the invention is to reduce the light halo, minimize spherical aberration, as well as restore vision both for distance and near.

The specified technical result is achieved by the fact that in the method of surgical correction of presbyopia in combination with simple hyperopic 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 optical surface lying within the entire optic zone (OZ), form in the form of a convex cylindrical surface, while forming a zone in the form of not removable inner Central segment (VVS), formed by two parallel chords and a circle with the diameter of the impact zone (SV), the center of symmetry of the VVS is combined with the center of the optical zones, and the axis of symmetry of the VCC lying parallel to the chords is combined with the strong axis of astigmatism, then a second optical surface is formed, then the surfaces of the transition zone are formed: the first surface of the transition zone (PPZ), with spliced with an outer edge with a cornea that is not subject to impact is formed as part of a 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 -0.1 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 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 of revolution, 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 hyperopic 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. 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.

Figure 3 is a top view of the area of the cornea.

Figure 4 - alignment of the axes of astigmatism.

5 is an increase in the area of the inner segment 13.

6 is a structure of a second optical surface 6.

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

Fig. 8 is an increase in the area of the central zone 20.

Fig.9 - the formation of the first 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.

12 is a frontal section through a surface 8.

Fig - the formation of a circular zone 25.

Fig - reduction of the circular zone 26.

Fig - reduction of the circular zone 27.

Fig - the formation of the second surface 9 of the transition zone.

17 is an isometric view of a surface 9.

Fig. 18 is a frontal section through a surface 9.

Fig - the formation of a circular zone 31.

Fig. 20 is a reduction in the circular zone 32.

Fig - reduction of the circular zone 33.

Fig is an isometric view of the mating surfaces 8 and 9.

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;

The first surface 8 of the transition zone;

The second surface 9 of the transition zone;

Transition Zone 10.

Figure 2 dots show the boundaries of the surfaces 5, 6, 8, 9, 4.

By 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, 9 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 11 refers to the zone in which the optical surfaces and the surfaces of the transition zone are formed.

The optical axis 12 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 surfaces of the transition zone 8, 9 are formed by sequential layer-by-layer removal of corneal regions. 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 convex optical surface 5 is formed that lies within the entire optical zone 7 by forming an inner central segment 13 (VCC) bounded by two parallel chords 14 and a circle with a radius of the irradiation zone 11 that cannot be removed and two symmetric outer segments 15 to be removed (Figure 4).

Mark up the VCC not subject to removal (Figure 4). The center of symmetry of the HVC is combined with the center 12 of the optical zone 7, the longitudinal axis 16 of the HVC is combined with the strong axis of astigmatism 17 (Figure 4).

Figure 4 shows, for convenience of presentation, the case where the strong axis 17 of astigmatism is vertical and the weak axis 18 is horizontal. In practice, cases with a different arrangement of the axes of astigmatism (not shown) are possible.

With each subsequent layered exposure, the area of the VCC 13 is increased (Figure 5). It increases until the distance between the chords 14 is equal to the diameter of the impact zone 11. In FIG. 5, the two symmetric outer segments 15 to be removed are shaded, and the HVC is not shaded. The spatial totality of all non-removable corneal HVCs, in which the area of the subsequent HVC is larger than the area of the previous HVC, creates a convex cylindrical optical surface 5, which allows one 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. 8). The surface 6 includes the center 12 of the optical zone 7.

The surface 6 is obtained by the formation of concentric rings 21 centered in the center of the optical zone, bounded by a circle with the radius of the impact zone 11, containing a circular central zone 22, not to be removed (Fig.9). 9, zone 22 is not shaded, and the concentric ring 21 is shaded.

Zone 22 during laser irradiation is not removed during the formation of the first corneal layer that changes in shape and each of the subsequent cornea that changes in shape to create a surface 6.

With each removed layer, an increase in the area of the central zone 22 and a reduction in the area of zone 21 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 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, 9 of the transition zone, which are the surfaces of the annular toroids. 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, surfaces 8, 9 are parts of a circular toroid and are formed by rotating segments of a circle around an optical axis without intersecting this axis.

The first surface 8 of the transition zone is formed as a part of the convex outer (CVP) surface of the first annular toroid (Figure 9). The surface 8 is formed by rotating the first flat segment 17 of the circle, convex towards the optical axis, around the axis 12 of surface 8 without intersecting axis 12. The arc of circle 18 of segment 17 is supported by a chord 19 located at an angle of 20 to axis 12 and lying with an axis of 12 one 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 21 to be removed, bounded by a circle with a radius of the impact zone 11, with a center 12 in the range from 0.04 to 0.2 of the diameter of the impact zone.

Frontal section of the surface 8, explaining the formation of circular zones 21, is shown in Fig.12. Subsequently, in each layer, the area of the circular zone 21 to be removed is reduced. Positions 22, 23 show the reduction of the circular zones 21. Figs. 13, 14, 15 show a layer-by-layer decrease in the area of the circular zones 21, 22, 23 (shaded in the drawings).

The surface of the transition zone 8 is mated with a portion of the cornea 4, not subject to laser exposure.

Then form the second surface 9 of the transition zone as a part of the concave inner surface of the second annular toroid. The surface 9 is formed by rotating the second flat segment 24 of the circle, convex in the direction opposite to the optical axis, around the optical axis 12 without intersecting this axis (Fig. 16). The arc of a circle 25 of segment 24 is based on a chord 26 located at an angle of 20 to axis 12 and lying with axis 12 in the same plane (Fig. 16). The surface 9 in isometric projection is shown in Fig.17.

The surface 9 is formed by the formation of circular zones 27 to be removed in the range from 0.04 to 0.2 of the diameter of the impact zone.

The frontal section of the surface 9, explaining the formation of circular zones 27, is shown in Fig. 18. Subsequently, in each layer, the area of the circular zone 27 to be removed is reduced (FIG. 19). Positions 28, 29 shows the reduction of circular zones 27 (Fig.20-21). Layer-by-layer reduction in the area of circular zones 27-29 in Figs. 19-21 is shown by shaded areas.

The second surface of the transition zone 9 is mated with the first surface 8 of the transition zone. An isometric view of this interface is shown in FIG.

It should be noted that the inner edge of the CVPI is combined with the outer edge of the CVPP, and the inner edge of the CVPN 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 with an energy per pulse 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, pulse repetition rate from 30 to 500 hertz.

Example 1: Patient A., 52 years old.

Condition before surgery:

Visual acuity in the distance: Vis OS = 0.4 cyl + 1.5 D ax 70 ° = 0.8

Near visual acuity: Vis OS = 0.3 sph + 1.75 D cyl + 1.5 D ax 70 ° = 0.8

Corneal curvature: 42.0 D - 70 °, 40.5 D - 160 °, average - 41.25 D.

Corneal thickness: 539 microns.

Diagnosis: Simple mild hyperopic astigmatism, presbyopia. The operation LASIK in accordance with the proposed invention.

Condition after surgery:

Visual acuity in the distance: Vis OS = 0.8

Near visual acuity: Vis OS = 0.8

Corneal curvature: 43.0 D - 70 °, 43.0 D - 160 °, average - 43.0 D.

Example 2: Patient E., 57 years old.

Condition before surgery:

Visual acuity in the distance: Vis OD = 0.4 cyl + 3.5 D ax 90 ° = 0.7

Near visual acuity: Vis OD = 0.1 sph + 2.0 D cyl + 3.5 D ax 90 ° = 0.7

Corneal curvature: 43.5 D - 90 °, 40.0 D - 0 °, average - 41.75 D.

Corneal thickness: 559 microns.

Diagnosis: Simple moderate hyperopic astigmatism, presbyopia. The operation LASIK in accordance with the proposed invention.

Condition after surgery:

Visual acuity in the distance: Vis OD = 0.5 cyl + 0.5 D ax 90 ° = 0.7

Near visual acuity: Vis OD = 0.6 cyl + 0.5 D ax 90 ° = 0.7

Corneal curvature: 43.5 D - 90 °, 43.0 D - 0 °, average - 43.0 D.

Example 3: Patient B., 53 years old. Condition before surgery:

Far visual acuity: Vis OD = 0.1 cyl + 4.0 D ax 15 ° = 0.6

Near visual acuity: Vis OD = 0.1 sph + 1.5 D cyl + 4.0 D ax 15 ° = 0.6

Corneal curvature: 44.0 D - 15 °, 40.0 D - 165 °, average - 41.5 D.

Corneal thickness: 564 microns.

Diagnosis: Simple hyperopic astigmatism of a high degree, presbyopia. The operation LASIK in accordance with the proposed invention. Condition after surgery:

Visual acuity in the distance: Vis OD = 0.5 cyl + 1.0 D ax 15 ° = 0.6

Near visual acuity: Vis OD = 0.6

Corneal curvature: 44.0 D - 15 °, 43.0 D - 165 °, average - 43.5 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 the diameter of the OZ; 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 hyperopic 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 hyperopic 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 convex cylindrical surface, while forming a zone in the form of by The center of symmetry of the central center of alignment is aligned with the center of the optical zone, and the axis of symmetry of the central circuit of parallel alignment with the strong chord axis is aligned with the strong axis of astigmatism, after which the transition surfaces are formed zone: the first surface of the transition zone (PPZ), conjugated by the outer edge with a portion of the cornea, not subject to exposure, is formed as part of a convex outer surface (CVP) of the first annular roida; 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 (CVT) of the second annular toroid, characterized in that the second optical surface is formed as a convex rotation ellipsoid 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 of the SC.

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