Method and device for shaping cornea

This invention relates to a method and apparatus for correcting a refractive error in an eye. The method and method of the present invention can modify the shape of individual parts of the eye and, in particular, produce permanent changes in corneal curvature.

- 2 Deviations from the normal shape of the corneal surface cause refractive errors in the visual process. Without resting, the eye focuses on the retina and focuses on distant objects. Such an eye can see distant objects without effort. Any deviation from this normal state is ametropia. This is a condition in which the resting eye cannot focus the image of a distant object on the retina. Hypermetropia or farsightedness is a refractive error in which, when the eye is at rest, parallel rays from distant objects are focused behind the retina. The scattering rays from nearby objects are further focused. In hypermetropia, the surface of the peritoneum is flattened and thus the angle of refraction of the rays of light as they pass through the refractive surfaces of the peritoneum is reduced. As a result, the light rays converge or focus at the point behind the retina. The retina is partly made up of nerve fibers that extend the optic nerve. The light waves on the retina are transformed into nerve impulses that are transmitted to the brain by the optic nerve, creating a sense of light there. In order to focus the parallel rays of light on the retina, the far-sighted eye must either adjust, i.e., increase the convexity of the eyepiece, or place a convex lens of sufficient intensity to focus the light rays on the retina.

Myopia or nearsightedness is a refractive state in which, with proper relaxation, parallel rays of light are focused in front of the retina. One of the reasons that usually causes myopia is the steeper curvature of the eyelid • · · · · · · · · · · · · · · ·

- 3 divorces. Thus, through the refractive surface of the cornea, the refraction of light rays converges or focuses on the larger and more refracted rays of light before the retina in the vitreous of the eye. When the rays of light reach this retina, they become divergent, forming a diffusion circle, resulting in a blurred image. For short-sightedness, a concave lens is used to correct eye focus.

The normal treatment of these classic shapes of the eye's refractive error is to wear glasses or contact lenses. Both have disadvantages for the user that are well known. Recent research focuses on a surgical modality designed to alter the refractive conditions of the eye. These are commonly referred to as keratorefractive methods. Such methods are keratophakia and keratomileusis. During keratomileusis, the peritoneal lamella is polished to form a meniscus or hypermetropic lens to correct myopia or nearsightedness. An optical corneal lathe has been specifically developed for this process. This lathe is also used in the keratophakia procedure, where interlamellar tissue is cut into a convex lens to correct aphakic hypermetropia. Transplanted tissue (corneal lamella) is frozen with carbon dioxide. The transplanted self-tissue is cut like a contact lens, which optically produces the desired optical correction of the peritoneum. In keratomileusis, the anterior cornea is formed with the lathe, and in keratophobia the corneal stroma of a donor's eye is formed with the lathe. These methods are widely used to correct large hypermetropic and myopic errors. In these procedures, the cornea is cut radially around the circumference of the tissue to be transplanted. This narrows the cornea and, as a result, the pressure of the fluids under the incisions penetrates the incisions and flattens the corneal curvature. This corneal collapse produces refractive errors in the eye that are not compensated for by the transplanted tissue. During these operations, suturing leads to radial asymmetry of the cornea, which contributes to astigmatic error. The sutures also cause scarring in the corneal tissue and the transparency of the scar tissue is removed. During surgical correction of astigmatism, the corneal curves are changed asymmetrically. A circumferential distortion force is easily illustrated; imagine a balloon inflated balloon that we squeeze between our palms. The surface area remains constant because the volume of air in the balloon is constant. The previously spherical anterior surface is distorted meridianly, as due to the compression of the diameter between the hands, the curvature changes without changing the circumference of the surface. The meridian of the balloon passing between the extended fingers becomes steeper, while the non-compressed meridian at right angles flattens as its diameter increases proportionally as the compressed diameter shortens. This illustrates the effect that small deviations from symmetrical patterns or intentional asymmetric patterns may have on surgical procedures and associated sutures. It can be seen that the current procedures of keratefraction methods should be used only in situations where other, conventional correction · · ··· {_φ· · · · · · · · · · · · · · · Proved to be ineffective. The limiting factor of these surgical techniques is thus the complexity of the leaves, which is caused both by the many incisions in the corneal tissue and by the complicated suture patterns. This leads to gross restructuring of the eye . It is thus a difficult task for the eye to adjust to this trauma.

In the last few years, the use of lasers to improve the shape of the cornea has been improved to eliminate refractive errors. These procedures involve the use of pulsed lasers to remove tissue from the cornea. The most commonly used type is an Exemer laser. Such a laser primarily acts on the tissue photochemically. It breaks down molecular bonds with such energy that tissue debris flies off the surface at a supersonic rate and leaves a discrete space. This method is called photodecomposition or photoablation (photoablation).

When using Exemer lasers, the beam must be applied to the eye in a controlled manner. For this purpose, the homogeneous (coherent) beam must be appropriately directed and controlled, since the optical elements must stand high energy photons and because the beam must be rendered non-uniform to form a new non-uniform optical surface of the cornea. Such a beam control system includes a variety of elements, including lenses for expanding or focusing the beam, mirrors for guiding the beam, modulators for beam homogenization, masking for beam shaping, and detector ♦♦ • · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · Current laser types range from simple lens and mask sets to sophisticated robots. In the latter, there are components that control not only the parameters of the laser but also the optical and mechanical elements. Because the process operates with submicron accuracy (less than 0.00001 meter), the requirements for the stability of such systems are stringent, even if the laser and the tissue interact only for microseconds.

Application of the system requires a high level of technical and biological control to modulate the corneal healing.

It is therefore an object of the present invention to provide a new and improved keratefraction method comprising a method and apparatus for changing the shape of the corneal optical zone. The purpose of the reshaping is to correct refractive errors - hypermetropia or farsightedness, myopia or nearsightedness and astigmatism - that cause minimal ophthalmic distortion and, through the simplicity of the method, virtually the possibility of error and the possibility of further complications from ocular disruption.

For this purpose, the method and apparatus of the present invention serve to carve or scarify the cornea to correct a refractive error.

It is a further object of the present invention to provide a mechanical device that can be used by a surgeon in a simple manner to carve or scarify the cornea to correct hypermetropia, myopia and astigmatism. This unit contains items that • · · · · ** ····························•

- Ί ensure depth and shape consistency of the surface.

It is a further object of the present invention to provide a plurality of incisions, carving and scarification of the outer frontal surface of the cornea to reshape the cornea and thereby correct refractive error so that inflammation does not occur or is minimized and the corneal epithelial layer re-grows in a minimum amount of time.

♦

It is a further object of the present invention to provide a re-profiled cornea of ​​the prior art such that the epithelial layer is re-grown from the unformed corneal portions without returning to its original curvature.

In accordance with the present invention, this object is achieved by applying a sharpened knife blade tangentially to the cornea and its top in the central geometric axis of the cornea, and then manually rotating or vibrating the blade about the geometric axis. the blade is scraped so late that the refractive error is essentially eliminated.

In a preferred embodiment of the method, a sharpened knife blade is tangentially pressed against the anterior surface of the cornea and its top. The sharpened knife blade is rotated or oscillated about a vertical axis substantially perpendicular to the corneal vertical axis to scrape the cornea. The blade is incrementally advanced axially to the cornea until the refractive error is limited.

In a further preferred embodiment of the method, the refractive error value is determined. A visual topographic keratogram is obtained from the cornea of ​​the eye. The visual keratogram is compared with a visual imaging device showing a corneal ray corrected for a given refractive error. A sharpened knife blade and a scraper are placed in a holding sleeve adjacent to and axial to the vertical axis of the cornea. Press the sharpened blade tangentially to the cornea. The scraper is rotated about the vertical axis and maintained. The keratogram is monitored until the refractive error is corrected.

The object with respect to the apparatus is solved by providing the apparatus with a profiling tool which includes a sharpened knife blade and with which the blade can be scraped to the desired radius. A device holds the knife blade tangentially to the cornea about its geometric axis. The tool is rotated or vibrated by a handpiece around the geometric axis and the blade is then scraped off by the blade so that the refractive error is substantially corrected.

Preferably, the device further comprises a means for incrementally advancing the blade to the cornea.

Preferably, the apparatus further comprises a display means for indicating the axial position of the profiling tool relative to the cornea.

Preferably, the knife blade comprises a plurality of radial blades having a lower, sharpened end which crosses the geometry axis of the profiling tool. Preferably, the blades are concave with respect to the geometry axis of the profiling tool.

• · · ·

Another preferred embodiment of the apparatus comprises a cylindrical positioning ring, a sliding sleeve, a profile tool and a means for moving the blade. On the underside of the cylindrical locating ring is an elastic vacuum ring, which is temporarily attached to the inhalation part of the eye and which surrounds the profuse cornea to be delivered. There are locating pins on the upper side of the seat ring. At the bottom of the support sleeve are elements that engage with the locking pins. The holder has an internal thread. The guide sleeve has an external thread for swivel engagement with the support sleeve. The profiling tool is pivotally and axially engaged in the holding sleeve and guide sleeve.

The profiling tool has a flange that rotates the tool on the guide sleeve. The blade moving device rotates or vibrates the blade relative to the eye's axis of vision.

The invention will now be described in more detail with reference to the accompanying drawings, in which:

First Figure 2 is a schematic horizontal sectional view of the eye;

Second Figure 3B is a schematic representation of a hypermetropic eye showing corneal application to reduce radius of curvature;

Third Figure 3B is a schematic representation of a myopic eye showing corneal adaptation to increase radius of curvature and thus flattening corneal slope;

4th Figure A detailed, schematic sectional view of the anterior part of the eye, with different layers of the cornea, showing the 'IQ _';

5th Fig. 6 is an exploded view of the main components of the apparatus of the invention;

6th Fig. 5 is a bottom view of the profHow tool according to Fig. 5

6-6 along line a

7th Fig. 4A is a plan view of the positioning ring according to the invention;

8th Figure 3 is a partial sectional view of another version of the profiling tool, a

9th Fig. 3A is a side view of another version of a scraping tool

10th Figure 10 is a longitudinal sectional view taken along line 10-10 of Figure 9;

11th Figure 3 is an installation diagram of an apparatus according to the invention with an electrical display device;

12th Figure 3 is a partial sectional view of another embodiment;

13th Figure 12 is a bottom view according to line 13-13 in Figure 12;

14th Fig. 3A is an enlarged sectional view of a locating ring on an eye.

Before describing the invention in detail, it is to be understood that the invention is not limited to the construction and arrangement details of the parts depicted in the accompanying drawings. There may be other embodiments of the invention and the invention may be practiced or implemented in various ways. The phraseology and terminology used herein are for purposes of illustration and are not limiting.

Figure 1 is a horizontal sectional view of the eye showing that the eyeball 11 is like a sphere having a frontal, protruding spherical portion, the cornea 12. so the eye actually consists of two slightly modified spheres, surrounded by one sphere ·

t · «· * · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · The smaller sphere in front of the two parts is the curved cornea.

The eyeball consists of three concentric sheaths that surround the various transparent media that light must pass through before reaching the photosensitive retina. The outermost casing is a wide protective part, the back five-fifths of which is white and opaque and is called 13 inhalations or - where the eyes are visible from the front. One-sixth of this outer layer in front is the transparent cornea 12.

The middle sheath is mainly vascular and has a function of nourishment. This envelope consists of the vascular 14, the radial body 16 and the iris 17. The function of the choroid is essentially retention of the retina. The role of radiation is to suspend and adjust the lens. The pasture part of the middle lining of the eye is the iris, which is located in a forehead. The iris is a thin, circular disc that corresponds to the camera aperture (blend) and has a circular aperture called 19 pupils near its center. The size of the pupil varies and this regulates the amount of light per retina. It also contracts the pupil to adjust, which sharpens focus by reducing spherical aberration. The iris is the 12 corneas and one in the back, 23 halls. The innermost part of the casing is the 18 retinas, which consist of nerve elements. These are the actual receptor part for visual impressions.

The retina is part of the brain like an outgrowth of the forebrain. One portion of the retina is connected to the forebrain as a nerve pathway by the optic nerve 24. On the anterior wall of the retina, directly on the dye

Under 12 epithelial tissue there is a layer of chopsticks and pins. The pins and sticks act as visual cells or photoreceptors that convert physical energy (light) into nerve impulses.

The vitreous 26 is a transparent, gelatinous mass that fills the back four-fifths of the eyeball. Its sides carry the 16 radial bodies and the 18 retinas. A front, cup-shaped recess includes the eyepieces 21.

The lens 21 is a transparent, crystalline refractive, double-convex body located between the iris 17 and the vitreous 26. Its axial diameter changes noticeably with adaptation. The radiation zone 27, consisting of transparent fibers between the body 16 and the lens 21, holds the lens in position and allows the radiation to act on the lens.

Returning to the cornea 12, this outermost fibrous transparent casing resembles a watch glass. It has a slightly greater curvature than the rest of the eyeball and is ideally spherical in nature. However, it is often more curved than one meridian, leading to astigmatism. The middle third of the cornea is the optic zone and has a slight flush outward as the cornea thickens towards its periphery. Refraction in the eye occurs mainly on the surface of the cornea.

Figure 2 shows an eyeball in which a normal curve 12 is depicted by a continuous line 39. When parallel rays of light 41 pass through the corneal surface 39 shown in Figure 2, these corneal surfaces are

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breaking to converge near the 18 retinas of the eye.

In Figure 2, the refractive effect of the lens or other parts of the eye is not considered for the purpose of the present disclosure. The eye of FIG. 2 is a hypermetropic eye and thus the rays of light 41 are refracted to converge at a point 42 behind the retina. When pressure is applied to the corneal rib 43, in the form of a circumferential rib, the corneal walls become steeper as the volume of the anterior chamber saline water 22 remains constant. Thus, the slope of the anterior cornea, including the optic zone (inner third of the cornea), increases and adopts the curvature of the dashed line 44 (increased distortion in the representation). The light rays 41 are then interrupted by the steeper surface 44 at a greater angle. Thus, the broken rays of light are focused at a smaller distance, for example directly on the retina 18.

Figure 3 shows an ophthalmic system similar to Figure 2, except that the so-called normal corneal curve of Figure 3 breaks the rays of light 41 so that they are focused at a point 46 in the vitreous, before the surface of the retina 18. This is typical of myopic eye. When the ribbon 43 of the cornea expands evenly outwardly as indicated by the arrows, the corneal walls become flatter. The corneal surface thus flattened breaks the light rays 41 at a smaller angle and converges to a more distant point, such as directly onto the retina 18.

Figure 4, a more detailed drawing of the anterior part of the eyeball, shows various layers of the cornea, including the epithelium 31

X or epithelium. The epithelial cells on its surface maintain the transparency of the cornea. Activation of these epithelial cells regulates the corneal bodies as well as the transport of water and electrolytes through the lamellae of the supporting tissue or stroma of the cornea. An anterior flanking plate 33, called the Bowman membrane, is located between the corneal epithelium 31 and the supporting tissue 32 or substania propria. The cornea is made up of lamellae which have parallel strips of fibrous material that frame the cornea as a whole. Most fibrous tapes are parallel to the surface, but some tapes - especially oblique to the front. The strips of fibers in each lamella are approximately perpendicular to the strips in the adjacent lamellae. The rear delimiter blades 34 are called Descemet membranes. It is a strong membrane firmly separated from the supporting tissue and resistant to the harmful processes of the cornea.

The posterior layer of the cornea is the 36 endothelium or endothelium, which consists of a single cell layer. The limbus 37 forms a transition zone between the conjunctiva 38 and the inhalation 13, and the cornea 12.

Fig. 5 is an exploded view of the assembly of the main components of the apparatus. Among the main components is a cylindrical locating ring 50. An elastic vacuum ring 52 protrudes from the underside of this locating ring and is applied to the eyes of the patient to be treated. The inside of the elastic vacuum ring 52 is connected by a vacuum hose 54 to the vacuum pump 56. Thus, the assembled parts remain in the eye for subsequent surgical procedures and the vacuum removes the scratched cornea

4 '····. The upper part of the positioning ring 50 has a plurality of positioning pins 58. These cylindrical pins are provided with a cylindrical retaining sleeve 60 such that the pivot pins fit into the holes 62 in the flange portion 64. The viewing opening 66 is used by the surgeon. On the outside of the cylindrical holding sleeve 60, there are longitudinal threads 68. The thread pitch is very small, for example 1.6 threads / mm (40 threads / inch). The body of the cylindrical sleeve has a pointer 70 which provides the surgeon with a visual measuring point for determining the position of rotation of a micrometer-like guide sleeve 72. The guide sleeve 72 has internal threads that engage the threads of the cylindrical holding sleeve. The guide sleeve has an outer button portion 74 and a scale 76 on its underside, for example millimeter or micrometer markings. The inner part 78 of the cylinder holding sleeve 78 is configured to rotatably receive a profiling tool 80. The profiling tool has a collar 82 that rests on the upper surface 83 of the guide sleeve 72 and moves up or down therewith. At the upper end of the profiling tool there may be a knurled knob 84 which is rotated and / or vibrated by the surgeon. At the bottom of the profiling tool there are a plurality of scraping, surgically sharp, blade blades 86 and 88 held in the body of the profiling tool 80 by pins 87, 89 and 91. Blades 86b and 88 are retained in the quad direction of the longitudinal axis of the profiling tool 80. The blades 86 and 88 of the present invention are made of surgical steel.

Figure 5 shows a profiling tool 80 for scraping or carving! surgery can be performed on the cornea, in the upper center, in case of myopic refraction, or in the case of myopia. This ································································································································································································································•

Third is shown. '

For correcting hypermetropia (vision) you can use the touch profiling tool shown in Figure 8. The tool has a 90 shank. Its construction is similar to that of the tool 80 of Fig. 5, except that a plurality of surgical steel knife blades 92, 94, and 96 at the lower end of the tool are transverse to the geometric axis of the tool and approximately 30 ° to the horizontal axis. is at an angle of 60 ° to the axis. The blades are configured to contact the outer frontal portion of the cornea to reduce its effective radius, i.e., the blades contact and scrape with the corneal area A of Figure 2, while the tool 80 of Figure 5 is the B of Figure 3. corneal area is carved or scraped.

During the operation of the device and during the surgical procedure, the first step is to measure the eye optically to determine the shape of the cornea for optically correct operation of the eye, i.e. to correct refractive errors. Typically, a keratographic photograph using a placido-ring target is used. The photograph reflects light reflected from placido rings on a regular spherical surface of the same size as the cornea in question, producing the same image as a topographic contour map. It is then followed by a topographic survey of the eye to be corrected for comparative purposes and that the surgeon receives the necessary diopter information to correct the refractive errors to correct the refractive errors. After that, the ···· * * ···························································

- Positioning ring 17 50 as shown in FIG. The size of this ring may be different for different surgeries, but preferably, the elastic vacuum ring 52 is concentric to the inhalation of the eye around the cornea. After inserting the ring 50, the cylindrical retaining sleeve 60 is placed there so that the pins 58 are inserted into the holes 62. The profile molding tool 80 is then inserted into the cylindrical support sleeve 60 in a position where the bottom of the blade blades 86 and 88 is in direct contact with the cornea. The surgeon may incrementally rotate the guide sleeve 71 by rotating the indicator arrow 70 and scale 76! operation depth. The cornea is scraped or carved by rotating or moving the profiling tool, although other mechanical or motor-operated tools may be used within the scope of the invention.

For myopia, the profiling tool 80 of Figure 5 is used. During the operation, the blade blades press on the corneal surface, which presses into contact with the blades on a larger surface. This increases the diameter of the carved surface. The effect of scraping or carving increases as the pressure between the cornea and the blade increases. The result is an increase in the radius of refraction of the cornea under the blade. When the tool is removed, the cornea regains its normal contour, except that the radius in the center is now longer than it originally was. As a result, the corneal refractive light is now focused on the retina. The surgeon achieves the scraping effect by rotating or moving the guide sleeve 72 in an incremental motion relative to the cylindrical holding sleeve 60, using the position of this incremental measuring scale 76 relative to the arrow 70 or other mark. The guide sleeve is typically provided with a pitch of 25 or 50 micrometers, so that each marked rotational pitch has one hundred millimeter adjustment. During use, the surgeon begins to determine the degree of downward movement required to change the cornea by rotating and / or vibrating the blades. Rotation for a few seconds removes a small amount of corneal material from the cornea. The tool may be removed and / or keratographic photographs may be taken to determine whether the refractive error has been corrected. Since the equipment and the surgical procedure are very small increments of motion in the process of corneal profiling, it is essential that the first contact be accurate. In many cases, the surgeon does this visually. In other cases, there may be electrical sensing elements between the cornea and the tool blade for fine adjustment of the tool. This allows a repeat amount of corneal detachment.

9 and 10 illustrate another embodiment of the apparatus. It has a 90 body, a recessed 192 handle and a knurled 194 button. In this embodiment, there is an inner gripper consisting of the scissor elements 196 and 198. The scissors rotate about the pin 100. The outer ends of the members have grooves 99 and 101 that engage the inner diameter of the retaining sleeve 60. A spring 102 expands the blades 104 and 106 of the blade at rest. When the blade shank 104 and 106 are clamped together, the shears 196 and 198 retract so that they can be inserted into the cylindrical holding sleeve 60. When the blade shafts are released, the shears 196 and 198 engage in frictional engagement with the inner circumference of the retaining sleeve 60. As shown in FIG.

Figure 11 shows an electrical display device whereby the surgeon determines the initial contact of the tool blades. A first contact electrode 110 is extensively coupled to the conductive body 190. The second electrode at ground 112 is grounded to the patient. The wires are connected to a low voltage power supply 114 having a signaling lamp 116. When the blade reaches the cornea, the lamp lights up and indicates the starting point of contact from which the downward movement measurement begins. Typically, a predetermined amount of corneal material is introduced into the tool by rotating the guide sleeve 72 downward. At this point, the rotation or vibration of the profiling tool 80 begins to alter the corneal contour. At this point, a measurement is made to determine whether corneal material still needs to be removed. If so, they set a new depth and repeat the procedure. The profiling tool is designed to be removable and replaceable without depth adjustment of the guide sleeve 72. The removal depth is typically 0.05 mm (0.002). In many cases, several cycles of surgery are required and measurements should be taken after each cycle. A computer-generated text of a nomogram and the corneal curves before and after each profiling process allows the surgeon to constantly monitor the amount of material removed from the epithelial layer and / or in some cases from the Bowman mucosa. The epithelial tissue was found to be restored to the profiled surface within 24 to 48 hours.

However, the Bowman membrane does not grow again and thus the modified beam remains. The epithelium restores and regains its original thickness and transparency, but with modified radius.

We performed a series of experiments on the eyes of rabbits. These resulted in consistent, repeatable changes in corneal shape. In these experiments, the apparatus of Fig. 5 and the profiling tool of Fig. 8 were used. The rabbits were anesthetized and the procedure described above was performed on the cornea of ​​the animals. The following table shows the corneal changes received in the cutting tool setup

<td colspan="3">the forebrain curvature relative to depth</td>

<td>change</td><td colspan="2">expressed.</td>

<td>Cornea</td><td>Radius mm</td><td>blade Depth</td>

<td>number</td><td>Forward curve After curve</td><td></td>

<td> 1</td><td> 7,05 7,70</td><td> 0,05</td>

<td> 2</td><td> 7,40 7,90</td><td> 0,05</td>

<td> 3</td><td> 8,00 8,70</td><td> 0,05</td>

<td> 4</td><td> 8,00 8,60</td><td> 0,025</td>

<td> 5</td><td> 7,22 7,70</td><td> 0,025</td>

<td> 6</td><td> 7,10 7,60</td><td> 0,026</td>

Figures 12 and 13 show a modified shape of the blade of the profiling tool. The blade shown in the figure is used to correct hypermetropia, but the same principle can be applied to miocomparative tools. More than 120 radially intersecting bodies • · ·

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122 there is a blade. The outer tip 124 of the sharpened end of each blade is bent, preferably at an angle of 120 °. The edges of the blades are alternately bent, as shown by the arrows in Figure 13.

Fig. 14 is an enlarged view of a placement ring 50 placed on one eye with a small vacuum gap holding the ring to the eye during surgery.