RU2366393C1 - Corneal flap formation technique in ametropia correction - Google Patents

Abstract

FIELD: medicine.

SUBSTANCE: invention concerns ophthalmology and can be used for formation of corneal flap in refractive surgical correction of ametropia. With using a femtosecond laser, intrastromal blind incisions are performed by three-stage resection. The operation procedure starts with an oblique incision with a corneal pedicle positioned at depth 100-300 mcm. The incision lies outside of perimetre of a prospected lateral incision. It is followed with a horizontal incision at depth 90 to 120 mcm, herewith forming a corneal flap of diametre 8.0 to 10.5 mm. Further, a partial vertical lateral incision is made at the angle 30-90 degrees to cornea surface herewith forming a flap pedicle of width 2.5-5 mm in upper, temporal or nasal position. The technical effect of the invention consists in maximally precise corneal position of the corneal flap of totally controlled diametre, thickness and morphology.

EFFECT: method allows reducing risk of postoperative complications, providing the minimum injuries of corneal biomechanics and enabling high functional results.

2 ex, 4 dwg

Description

The invention relates to medicine, and more specifically to ophthalmology, and can be used to form a corneal flap in refractive surgery to correct ametropia.

Ametropia is the most common cause of decreased vision in people of a young, working age. The medical and social problem of myopia, hyperopia and astigmatism is to limit the choice of profession, sports, military service. Therefore, the problem of improving vision with refractive errors for many years remains one of the relevant topics in ophthalmology.

A known method of forming a corneal flap for the correction of ametropia using a microkeratome followed by laser ablation of the corneal stroma (Kurenkov V.V. Guide to excimer laser surgery of the cornea. - M .: Publishing House of the Russian Academy of Medical Sciences, 2002. - p.203-206). The method allows for excimer laser exposure to correct refractive disorders within the stroma of the cornea, and the creation of a corneal flap provides a short rehabilitation period.

The disadvantage of this method is the formation of a thick corneal flap with a microkeratome within 130-160 μm, the uneven thickness of the formed corneal flap with a deviation of 20-40 μm, violation of the architecture of the stroma and biomechanics of the cornea, the possibility of surgical complications in the form of too thin a flap of small diameter, incomplete flap, full flap a cut of the flap or its half, an eccentrically located flap, receiving a hole in the center of the flap. All this leads to the induction of postoperative aberrations of higher order, which may cause a decrease in possible functional results and quality of vision.

The objective of the invention is to develop a safe, highly predictable and effective method of forming a corneal flap.

The technical result of the invention is to achieve the most accurate location of the corneal flap on the cornea with full control of the diameter, thickness, morphology of the flap and a decrease in the risk of postoperative complications, which leads to minimal disturbances in the biomechanics of the cornea and helps to achieve high functional results.

The technical result is achieved by the fact that in the method of forming a corneal flap according to the invention, intrastromal non-through incisions are performed by a femtosecond laser by means of a three-stage resection, first, an incision is made in the position of the corneal flap leg located outside the perimeter of the planned lateral incision at a depth of 100-300 μm, then a horizontal incision at a depth of 90 to 120 microns, and then an incomplete lateral incision at an angle of 30-90 degrees to the surface of the cornea with the formation of a flap leg 2.5-5 mm with a loop angle of 45 -90 degrees in the upper, temporal or nasal position with a variation in the diameter of the corneal flap from 8.0 to 10.5 mm, while the incision begins in the loop position and ends on the opposite side of the cornea on the periphery.

The invention is illustrated by drawings (figures 1-4).

Figure 1-3 shows a diagram of the formation of a corneal flap using a femtosecond laser: figure 1 is a top view, figure 2 is a side view in section, figure 3 is a view a from figure 2 (enlarged). Position 1 indicates the diameter of the corneal flap, 2 - the corneal flap, 3 - the corner of the loop, 4 - pocket, 5 - the leg of the flap, 6 - the thickness of the flap, 7 - vertical section, 8 - horizontal section, 9 - angle of the lateral incision.

Figure 4 - diagram of the scanning program Raster, according to which the incision begins in the position of the loop on the periphery of the lid, the laser pulses create a linear chord across the field of the incision with the intersection of the perimeter of the flap, which moves according to the scheme from one edge of the cornea to the other, filling a circular disk, and ends on the opposite side of the cornea.

The treatment method according to the invention is as follows.

The IntraLasik operation is performed using an IntraLase FS femtosecond laser using infrared neodymium laser laser with a wavelength of 1053 nm, a pulse repetition rate of 60 kHz, a pulse duration of 600-800 f / s, and a maximum laser pulse power of 12 mV.

The formation of corneal flap 2 is performed under local anesthesia using a femtosecond laser, controlling its formation using the IntraLasik control computer program, and the IntraLase sterile disposable interface containing a collection aspiration ring, applanation lens, vacuum tube and disposable syringe. A vacuum system consisting of pre-sterilized suction rings connected by means of a vacuum tube with a disposable syringe is applied to the eye, the applanation lens connected to the laser system is lowered, non-through incisions are made using a laser beam under the control of a computer program through a three-stage resection. In this case, a pocket 4 is first formed for evacuating the gas mixture generated during the creation of the corneal flap 2, for which an inclined incision is made at the position of the leg 5, which is outside the perimeter of the planned vertical section 7 at a depth of 100-300 μm. Then a horizontal incision 8 is performed at a depth of 90-120 μm according to the Raster scanning scheme, according to which the incision begins in the position of the leg of loop 3 on the periphery of the lid, laser pulses create a linear chord across the incision field with the intersection of the perimeter of the corneal flap 2, which moves according to the scheme from one the edges of the cornea to another, filling a round disc and ending on the opposite side of the cornea at the periphery. Next, an incomplete vertical incision 7 is performed, extending from the horizontal plane of incision 8 to the corneal surface at an angle of 30-90 degrees to the corneal surface with the formation of the flap leg 5 with a width of 2.5-5 mm and a loop angle 3 of 45-90 degrees, which determines the width legs of the corneal flap in the upper, temporal or nasal position. As a result of this, a corneal flap 2 is formed with a thickness of 90-120 μm, a diameter of 1 from 8.0 to 10.5 mm and a cut-in angle of 9 from 30 to 90 degrees with a loop angle of 3 from 45 to 90 degrees, followed by an applanation lens and a vacuum system removed from the eye. Corneal flap 2, formed using a femtosecond laser, is separated with a spatula, it has a leg for 12 hours, then excimer laser ablation of the corneal stroma is performed according to a predetermined algorithm, the bed of corneal flap 2 is cleaned with a balanced saline solution, the flap 2 is put in place, the conjunctival cavity is placed in place. antibiotic.

The method allows you to fully control the diameter from 8.0 to 10.5 mm with a deviation from the planned no more than ± 0.09 mm, a thickness of 90-120 μm with an average forecast accuracy of ± 10 μm, centering and morphology of the flap due to strict resolution criteria laser control program, forms a uniformly thin ("flat") corneal flap, which helps to increase functional results, reduces the risk of postoperative complications, and reduces the possibility of inducing postoperative aberrations.

The induction of higher order aberrations using a femtosecond laser is insignificant in comparison with the operation of a mechanical microkeratome and does not affect the acuity and quality of vision after refractive surgery, which is confirmed by the study of spatial contrast sensitivity.

In the postoperative period, corticosteroids are instilled during the first week 3 times a day, during the second week - 2 times a day, during the third - 1 time per day, as well as drops with an antibiotic or antiseptic 3 times a day for 7 days.

The choice of laser exposure parameters was confirmed by experimental studies on donor eyes, electron microscopy, and computer analysis of the quantitative and qualitative state of corneal cells.

The proposed method is illustrated by the following examples.

Example 1. Patient M., 32 years old, diagnosis: high degree myopia of the right eye, complex myopic astigmatism, weak amblyopia, moderate myopia of the left eye. Visual acuity of the right eye OD = 0.04 sph - 6.0 cyl - 1.0 ax 109 = 1.0; keratometry: 45.5 ax 42 degrees, 44.25, refractometry under conditions of cyclophlegia sph -6.25 cyl -1.5 ax 113 degrees, the length of the right eye is 26.2 mm, pachymetry in the central zone is 506 microns. Visual acuity of the left eye is 0.05 sph -4.25 = 1.0, refractometry under conditions of cyclophlegia sph -4.5, keratometry: 45.00 ax 113 degrees, 44.25, eye length 24.98 mm, central pachymetry zone 509 microns. Spatial contrast sensitivity for 6 frequencies before surgery is an average of 41 centigrade / deg. RMS wavefront error for higher order aberrations (RMS HO) 0.297 microns.

The patient under local anesthesia with the IntraLase FS femtosecond laser performed the procedure of forming a corneal flap with the following parameters: thickness 120 μm, diameter 8.8 mm and angle of incision 45 degrees. The flap was separated with a spatula and had a leg at 12 o’clock, then photoablation was carried out with the corresponding operation algorithm for myopia. The residual corneal thickness after ablation on the right eye is 276 microns, on the left - 282 microns. The postoperative period was uneventful. After the operation, tobrex, indocollyr, and balarpan were applied locally; on the day after the operation, 0.01% of dexamethasone solution was prescribed according to the 4-week schedule.

At discharge, visual acuity of the right eye of 0.7; keratometry 39.5 ax 74 / 38.5, visual acuity of the left eye 1.0; keratometry 40.5 ax 100 / 40.0. An increase in uncorrected visual acuity was obtained from 0.05 to 0.7 in the right eye and from 0.05 to 1.0 in the left eye.

OST data of the anterior segment at discharge: corneal flap thickness 121 ± 5 μm, diameter - 8.8 mm, RMS HO 0.56 μm, spatial contrast sensitivity for 6 frequencies on average 46 c / deg.

Example 2. Patient B., 45 years old, diagnosis: OD - mild hyperopia, presbyopia, mild hyperopia, weak amblyopia of the left eye.

Visual acuity of the right eye 0.7 sph + 1.0 = 1.0.

Visual acuity of the left eye 0.1 sph + 4.5 = 0.4; keratometry: 42.0 ax 107 degrees / 41.25, refractometry under conditions of cyclophlegia sph + 4.75, pachymetry in the center of the cornea 530 microns, paracentral zone 3 mm - 543 microns, 7 mm from the center - 614 microns, RMS HO 0.345 microns, spatial contrast sensitivity for 6 frequencies an average of 38 c / deg.

The patient under local anesthesia with the IntraLase FS femtosecond laser performed the procedure of forming a corneal flap with the following parameters: thickness 120 μm, diameter 9.5 mm and cut angle 45 degrees. The flap was separated with a spatula and had a leg at 12 o’clock, then photoablation was performed with the corresponding operation algorithm for hyperopia. The residual corneal thickness after ablation is 292 microns.

The postoperative period was uneventful. After the operation, tobrex, indocollyr, and balarpan were applied locally; on the day after the operation, 0.01% of dexamethasone solution was prescribed according to the 4-week schedule.

At discharge, the visual acuity of the left eye is 0.4; keratometry 48.25 ax 100 / 47.5. An increase in uncorrected visual acuity was obtained from 0.1 to 0.4 in the left eye.

OST data of the anterior segment: corneal flap thickness 123 ± 4 μm, diameter 9.5 mm. RMS HO 0.419 μm, spatial contrast sensitivity for 6 frequencies on average 42 c / deg.

According to the proposed method, 80 patients were operated on. In all cases, the most accurate location of the corneal flap on the cornea was achieved, and high functional results were obtained.

Thus, the proposed method of forming a corneal flap for correcting ametropia using a femtosecond laser is highly accurate, safe and effective. Compared with the prototype, the method contributes to a significant increase in functional results and the quality of vision after refractive surgery due to full control over the parameters of a flat and thin corneal flap. Using the proposed method of treatment contributes to the social and professional rehabilitation of patients.

Claims (1)

A method of forming a corneal flap for correcting ametropia followed by excimer laser ablation of the stroma of the cornea, characterized in that intrastromal non-through incisions are performed with a femtosecond laser by means of a three-stage resection, while an oblique incision is first made at the position of the corneal flap at a depth of 100-300 μm, which is outside the perimeter side cut; then a horizontal incision is made at a depth of 90 to 120 μm, forming a corneal flap with a diameter of 8.0 to 10.5 mm; then an incomplete vertical lateral incision is made at an angle of 30-90 ° to the surface of the cornea with the formation of a flap leg 2.5-5 mm wide in the upper, temporal or nasal position.

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