RU2514872C1 - Method for surgical correction of presbyopy combined with compound 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 optical surface is formed first at two stages in the form of a hyperbolic paraboloid surface. First, a concave portion of the hyperbolic paraboloid surface is formed by limiting a removable centre. The above portion of the paraboloid surface is formed within the entire optical cornea (OC). A centre of central symmetry matches with the OC centre. That is followed by forming a convex portion of the hyperbolic paraboloid surface by limiting a non-exposed centre. A centre of central symmetry matches with the OC centre. An axis of central 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. The diameter of the second optical surface is related to the diameter of the OC as a value within the range of 0.85 to 0.95. Then, the transitions surfaces (TS) are formed. The first TS is formed as a portion of a convex outer surface of a first O-toroid. A width of the first TS makes 0.04 to 0.2 diameters of the exposure. The first TS is formed so that its outer border is coupled with the non-exposed cornea. The second TS is formed as a portion of a concave inner surface of a second O-toroid having a width of 0.04 to 0.2 diameters of the exposure. The inner border of the second TS shall be coupled with the outer border of the first optical surface, and its outer border - with the inner border of the first TS.EFFECT: high far and near visual functions with no additional spectacle correction with a decreased light cap and minimised spherical aberration.27 dwg, 3 ex

Description

The invention relates to ophthalmology and can be used in the correction of presbyopia in combination with mixed astigmatism. The problem of correcting presbyopia in combination with mixed 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 6% of all presbyopes suffer from presbyopia in combination with mixed astigmatism. All this makes the problem of presbyopia correction in combination with mixed astigmatism one of the urgent problems of ophthalmology.

The well-known "Method of surgical correction of presbyopia in combination with mixed astigmatism" according to patent RU No. 2314073, A61F9 / 01, priority date 25.04.2006

The method includes exposure to the cornea of the eye by the radiation of an excimer laser with the formation of optical surfaces and surfaces of the transition zone (PPZ) by sequential layer-by-layer removal of cornea. The first optical surface in the form of a surface of a hyperbolic paraboloid is formed in two stages. First, a concave part of the surface of the hyperbolic paraboloid is formed, lying within the entire optical zone (OZ), by forming the central zone (CZ) to be removed. The center of symmetry of the central zone is combined with the center of the central zone. Next, a convex part of the surface of the hyperbolic paraboloid is formed by the formation of a centralized zone not subject to influence. The center of symmetry of the central center is combined with the center of the central zone, and its axis of symmetry is combined with the weak axis of astigmatism. The second optical surface is formed in the form of a convex spherical surface, its optical axis coincides with the center of the OZ, and the diameter of the second optical surface is 0.28-0.55 of the diameter of the OZ. The first surface of the transition zone (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 is mated to the outer edge of the first optical surface, and the outer edge of the second PPZ is mated to 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 mixed astigmatism in order to provide 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 light halo, minimize spherical aberration, as well as restore vision both for distance and near. The specified technical result is solved by the fact that in the method of surgical correction of presbyopia in combination with mixed astigmatism, including exposure to excimer laser radiation with a wavelength of 193-222 nanometers, with an pulse energy of 0.8-2.1 millijoules, with a laser spot diameter of 0.5-1.5 mm, duration pulses of 5-8 nanoseconds, the pulse repetition rate from 30 to 500 hertz per cornea of the eye, the optical surface and the surface of the transition zone (PZ) are formed by sequential layer-by-layer removal of corneal sites, initially o form the first optical surface in the form of a hyperbolic paraboloid, first form its concave part lying within the entire optical zone (OZ), by forming a central zone (CZ) to be removed, and two symmetric peripheral zones that cannot be removed, while the CZ bounded by two diametrically opposite circular arcs with the radius of the external impact zone and two curved lines that are sections of two symmetric branches of the first hyperbole, mark the central area to be removed, aligning the center the center of symmetry of the central zone with the center of the optical zone, the axis of symmetry passing through the vertices of the hyperbolas is combined with the strong axis of astigmatism, with each subsequent layer-by-layer exposure the central area is reduced by decreasing the distance between the vertices of the hyperbolas from a value equal to the diameter of the zone of influence to zero, then the formation of the first optical surface by forming the second convex part of the surface of the hyperbolic paraboloid, forming two symmetric peripheral zones to be affected, and the Central zone (CZ), which is subject to action, while the central zone is bounded by two diametrically opposite circular arcs with the radius of the external impact zone and two curved lines that are sections of two symmetric branches of the second hyperbola, mark the central zone that is not to be affected by combining the center of symmetry of the central center with the center of the optical zone, the axis of symmetry, passing through the vertices of the second hyperbole, combine with the weak axis of astigmatism, with each subsequent layered exposure, increase the area of the central area by increasing the distance between the vertices of the erbol from zero to a value equal to the diameter of the impact zone; then form a second optical surface, the optical axis of which coincides with the center of the optical zone; then form the first 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 the diameter of the SV connected by the outer edge of the first PPZ with the cornea section not to be affected, in the form of a part of the convex outer surface (CVP) ) of the first annular toroid formed by the rotation of the first flat segment of a circle turned by the arc of the segment toward the optical axis, around the optical axis without intersecting this axis, while the circular arc of this segment rests on the chord located under glom to the optical axis with the optical axis lying in a plane, wherein the first HAG formed by circles, to be removed, with the center at the center of the optical zone, the outer diameter of which decreases in layers; then a second SCF is formed, within the area of the SC, lying in the range from 0.04 to 0.2 of the diameter of the SC connected by the inner edge of the second SCF with the outer edge of the first optical surface, and the outer edge of the second SCF with the inner edge of the first SCF, as a part of the concave inner surface ( FWM) of the second annular toroid, by rotating the second flat segment of the circle, facing the arc of the segment toward the opposite optical axis, around the optical axis, without intersecting this axis, while the circular arc of this segment is supported a chord, at an angle to the optical axis equal to the angle of inclination CHVNP chords, and with the optical axis lying in a plane, wherein this surface is formed by circles, to be removed, with the center at the center of the optical zone, the outer diameter of which decreases in layers; according to the invention, 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.

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 mixed 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.1-27. 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 is an isometric view of the surface 5.

Figure 5 - the formation of a concave part of the surface 5.

6 is an isometric view of the formation of a concave part of the surface 5.

7 - alignment of the axes of astigmatism.

Fig. 8 is an isometric view of the concave portion of a hyperbolic paraboloid.

Fig.9 - the formation of a concave part of the surface 5.

Figure 10 is an isometric view of the formation of the convex part of the surface 5.

11 is a structure of a second optical surface 6.

Fig - the formation of the second optical surface.

Fig. 13 is an increase in the area of the central zone 30.

Fig - the formation of the first 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 35.

Fig - reduction of the circular zone 36.

Fig - a further decrease in the circular zone 37.

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

Fig is an isometric view of the surface 9.

Fig - frontal section of the surface 9.

Fig.24 - the formation of a circular zone 41.

Fig - reduction of the circular zone 42.

Fig - reduction of the circular zone 43.

Fig.27 is an isometric view of the conjugation of surfaces.

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:

First optical surface 5.

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 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 whose shape 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.

The first optical surface 5, lying within the entire optical zone 7, is formed in the form of a hyperbolic paraboloid. Figure 4 presents the isometry of the surface 5. The saddle-shaped surface of the hyperbolic paraboloid has a concave part 13 and a convex part 14 (Figure 4).

Initially, the first concave part of the optical surface of the hyperbolic paraboloid is formed, lying within the entire optical zone (OZ), by the formation of the central zone (CZ) 15 to be removed, and two symmetric peripheral zones 16 that cannot be removed. In this case, the central lock 15 is limited by two diametrically opposite circular arcs with a radius of the external impact zone 11 and two curved lines that are sections of two symmetric branches of the first hyperbole 17 (Figure 5).

The CZ 15 to be exposed is marked, combining the center of symmetry of the CZ 18 with the center 12 of the optical zone 7, the axis of symmetry 19 passing through the vertices 20 of the hyperbolas 17 is combined with the strong axis of astigmatism 21 (Figure 5).

An isometric view of the formation of the concave part of the surface 5 and the position of the central lock 15 to be exposed, shown in Fig.6.

The peripheral zones 16 during laser irradiation are 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 5.

5, for convenience of presentation, shows the case where the strong axis 21 of the 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 central area 15 is reduced by decreasing the distance 22 between the vertices 20 of the hyperbolas from a value equal to the diameter of the exposure zone to zero (Fig. 7). All first hyperbolas have 23 common asymptotes, with the angle formed by the intersecting asymptotes lying in the range from 6 degrees to 84 degrees.

In FIGS. 5, 7, two symmetrical peripheral zones 16 that cannot be removed are not hatched, and the central lock 15 is hatched.

An isometric view of the concave portion of a hyperbolic paraboloid is shown in FIG.

The formation of the optical surface of the hyperbolic paraboloid is continued by the formation of the second convex part of the surface of the hyperbolic paraboloid.

Two symmetric peripheral zones are formed that are subject to 24 and a central zone (CZ) 25 that is not affected (Fig. 9).

In this case, the central lock 25 is limited by two diametrically opposite circular arcs with a radius of the outer impact zone 11 and two curved lines that are sections of two symmetric branches of the second hyperbola 29 (Fig. 9).

The central axis 25, which is not subject to influence, is marked, combining the center of symmetry of the central center 26 with the center 12 of the optical zone 7, the axis of symmetry 27 passing through the vertices 28 of the second hyperbole 29 is combined with the weak axis of astigmatism 30 (Figure 5).

The central zone 25 during laser exposure 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 5.

With each subsequent layer-by-layer exposure, the area of the central area is increased by increasing the distance 31 between the vertices 28 of the hyperbolas 29 from zero to a value equal to the diameter of the exposure zone (Fig. 9).

All second hyperbolas have 23 common asymptotes that coincide with the asymptotes of the first hyperbolas.

In Fig. 9, two symmetric peripheral zones 24 to be removed are shaded, and the central door 25 is not shaded. The spatial totality of all corneal cortex that cannot be removed, in which the area of the subsequent cep is larger than the area of the previous cus, creates a convex part of the optical surface of a hyperbolic paraboloid.

An isometric view of the formation of the convex part of the surface 5 and the position of the peripheral zones 24 to be affected is shown in FIG. 10.

The successive creation of a concave and convex part of the surface of the hyperbolic paraboloid leads to the formation of the optical surface of the hyperbolic paraboloid 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 with a negative conical constant from -0.1 to -0 , 4 (Fig. 11). The surface 6 includes the center 12 of the optical zone 7.

The surface 6 is obtained by forming concentric rings 32 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 33, not to be removed (Fig.12). 12, zone 33 is not shaded, and the concentric ring 32 is shaded.

Zone 33 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 33 and a reduction in the area of zone 32 are performed (Fig. 13).

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 part of the convex outer (CVP) surface of the first annular toroid (Fig. 14). The surface 8 is formed by rotating the first flat segment 34, convex towards the optical axis, around the axis 12 of surface 8 without intersecting axis 12. The arc of circle 35 of segment 34 is based on the chord 36, located at an angle of 37 to axis 12 and lying with the axis 12 in one plane (Fig. 14). Top view of the surface 8 in Fig.15. The surface 8 in isometric projection is shown in Fig.16.

The surface 8 is formed by the formation of circular zones 38 to be removed, bounded by a circle with the radius of the impact zone 11, with the center 12.

The frontal section of the surface 8, explaining the formation of circular zones 38, is shown in Fig.17. Subsequently, in each layer, the area of the circular zone 38 to be removed is reduced in layers. Positions 39, 40 show a decrease in circular zones 38. Figs. 18, 19, 20 show a layer-by-layer decrease in the area of circular zones 38, 39, 40 (shaded in the figures).

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 in the form of a portion of the concave inner surface (CVP) of the second annular toroid. The surface 9 is formed by the rotation of the second flat segment 41, facing the opposite optical axis, around the optical axis 12 without intersecting this axis (Fig.21). The arc of the circle 42 of the segment 41 is based on the chord 43 located at an angle of 37 to the optical axis 12 of the CVT of the second toroid (Figure 21). The surface 9 in isometric projection is shown in Fig.22.

The surface 9 is formed by forming circular zones 41 to be removed.

The frontal section of the surface 9, explaining the formation of circular zones 44, is shown in Fig.23. Subsequently, in each layer, the area of the circular zone 44 to be removed is reduced in layers. Positions 45, 46 shows the reduction of the circular zones 44 (Fig.24-26). The layer-by-layer reduction in the areas of circular zones 44-46 in Figs. 24-26 is shown by shaded areas.

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

It should be noted that the inner edge of the PVI is combined with the outer edge of the PVI, and the inner edge of the PVI 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 with laser spot diameter 0.5-1.5 mm, 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 O., 54 years old.

Condition before surgery:

Visual acuity in the distance: Vis OS = 0.4 sph + 1.0 D cyl - 1.5 D ax 0 ° = 0.9

Near visual acuity: Vis OS = 0.2 sph + 1.5 D cyl + 1.5 D ax 90 ° = 0.9

Corneal curvature: 43.0 D - 0 °, 40.5 D - 90 °, average - 41.75 D.

Corneal thickness: 567 microns.

Diagnosis: Mixed astigmatism, presbyopia.

The operation LASIK in accordance with the proposed invention.

Condition after surgery:

Visual acuity in the distance: Vis OS = 0.9

Near visual acuity: Vis OS = 0.9

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

Example 2: Patient E., 58 years old.

Condition before surgery:

Visual acuity in the distance: Vis OS = 0.1 sph -1.0 D cyl + 2.5 D ax 90 ° = 0.6

Near visual acuity: Vis OS = 0.2 sph + 1.5 D cyl + 2.5 D ax 90 ° = 0.6

Corneal curvature: 42.0 D - 90 ° 44.5 D - 0 °, average - 43.25 D.

Corneal thickness: 528 microns.

Diagnosis: Mixed astigmatism, presbyopia.

The operation LASIK in accordance with the proposed invention.

Condition after surgery:

Visual acuity in the distance: Vis OS = 0.6

Near visual acuity: Vis OS = 0.6

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

Example 3: Patient K., 56 years old.

Condition before surgery:

Visual acuity into the distance: Vis OS = 0.1 sph + 1.5 D cyl - 3.5 D ax 0 ° = 0.8

Near visual acuity: Vis OS = 0.2 sph + 0.5 D cyl + 3.5 D ax 90 ° = 0.8

Corneal curvature: 42.75 D - 0 ° 39.25 D - 90 °, average - 42.0 D.

Corneal thickness: 563 microns.

Diagnosis: Mixed 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 = 0.6 sph + 0.5 D = 0.8

Corneal curvature: 41.5 D - 0 ° 41.5 D - 90 °, 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 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 in combination with mixed astigmatism while maintaining the asphericity of the corneal surface to ensure high visual functions in the distance and near without additional spectacle correction while reducing the light halo and minimizing spherical aberration .

Claims (1)

A method of surgical correction of presbyopia in combination with mixed 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: initially form the first optical surface in the form of a hyperbolic paraboloid, first form its concave part lying within the entire optical zone (OZ), by the central zone (CZ) to be removed and two symmetrical peripheral zones not to be removed, while the CZ is bounded by two diametrically opposite circular arcs with the radius of the impact zone (CB) and two curved lines that are sections of two symmetric branches of the first hyperbola, the center of symmetry of the CZ is combined with the center of the OZ, the axis of symmetry passing through the vertices of the first hyperbole is combined with the strong axis of astigmatism, with each subsequent layer-by-layer exposure, the area of the ZZ is reduced by decreasing the distance standing between the vertices of the first hyperbola from a value equal to the diameter of the zone of influence to zero, then they continue to form the first optical surface by forming the second convex part of the surface of the hyperbolic paraboloid, thus forming two symmetrical peripheral zones to be removed and a central zone (CZ) not to be removed, in this case, the center is bounded by two diametrically opposite circular arcs with a radius of 3B and two curved lines, which are sections of two symmetric branches of the second hyperb For example, the center of symmetry of the central zone is combined with the center of the central zone, the axis of symmetry passing through the vertices of the second hyperbola is combined with the weak axis of astigmatism, with each subsequent layer-by-layer action, the central zone is increased by increasing the distance between the vertices of the second hyperbola from zero to a value equal to the diameter of the zone of influence, in this case, the asymptotes of the first and second hyperbolas coincide, then form a second optical surface, the optical axis of which coincides with the center of the OZ, then form the surface of the transition zone: the first over the transition zone (PPZ), conjugated by the outer edge with the corneal area not to be affected, 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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