RU2294723C2 - Method for carrying out personal laser keratomylesis operation - Google Patents

Abstract

FIELD: medicine.

SUBSTANCE: method involves determining aberration by measuring wave front of optical eye tract. Stroma ablation is carried out. Personal ablation is calculated before the operation and 30% adjustment is applied for increasing ablation on high order aberrations like the fourth and fifth.

EFFECT: enhanced effectiveness in achieving maximum vision improvement with single laser radiation treatment.

Description

The invention relates to medicine, in particular to laser refractive ophthalmic surgery, and can be used to correct refractive errors of varying degrees.

A known method of correcting myopia using laser keratomileusis (RF patent No. 2189209, dated January 29, 2001, dated February 20, 2002, Bi No. 26) based on a single ablation of corneal stroma. There are also known methods involving the correction in 2 stages: sequential execution of radial keratotomy and Lasik (RF patent No. 2147423 from 04/20/2000) and repeated Lasik (RF patent No. 2147854 from 04/27/2004).

In the known methods of treatment, the aberrations of the eye are not determined and are not eliminated - optical errors characteristic of the eye, like any optical system (Fedorov Readings, Moscow, 2002, p. 52-53; ophthalmology, volume 1, number 2 , 2004, S. 27-33, J. Refractive surgery and ophthalmology, 3 No. 1, 2003, S. 5-13).

The presence of aberrations does not allow the surgeon to obtain high vision during the operation.

The closest in technical essence and the achieved result to the proposed method of treatment is a method protected by RF patent No. 2228730, s. 04.16.2003, op. May 20, 2004, Bi No. 14. (prototype). In accordance with the indicated method, the operation is carried out in two stages: multizonal ablation is performed with a decrease in the degree of myopia, then the optical tract is scanned to determine lower and higher order aberrations, after which ablation is repeated taking into account the revealed aberrations. The disadvantages of this method include:

- the need for 2-fold ablation of the cornea with a laser;

- The terms of treatment and final rehabilitation after surgery are lengthened.

The objective of the invention is to develop an effective, gentle way to conduct a personalized Lasik operation that provides the greatest possible visual acuity. The essence of the invention lies in the fact that they carry out preoperative measurement of the wavefront of the optical path of the eye and determine the available aberrations, the values of which calculate the personalized ablation, while making a correction of 30% for aberrations of the 4th and 5th orders that increase with laser keratomileusis.

The technical result achieved by the implementation of the invention:

- one-stage elimination of aberrations, both preoperative and induced as a result of keratomileusis, is carried out;

- the maximum visual acuity possible for a given eye is achieved;

- reduced postoperative rehabilitation;

The method is as follows:

The patient determines the preoperative clinical refraction, measure the maximum possible visual acuity using spectacle correction. Measure the thickness of the cornea using keratopachymetry. Next, aberrometry of the entire optical path of the eye is performed using a Multispot 250 digital scanning aberrometer. The basis of this device is the Shack-Hartmann wavefront sensor. The basic principle of the wavefront sensor is as follows. A low-power laser beam focuses with the eye on the retina and creates a small spot. Scattered laser radiation is reflected back and acquires aberrations caused by the intraocular medium, the lens and the cornea. The radiation received from the eye passes through a confocal lens refraction compensator, which eliminates the spheroequivalent. Then the radiation falls on a polarizing beam splitter, which reduces stray glare from the cornea. Then the radiation enters the microlens raster, which is optically conjugated with the pupil of the studied eye. The raster has a pitch of 200 μm and the total number of its microlenses is 250. The lens raster forms an array of focal spots "Hartmannogram" in the plane of the CCD of the image sensor. Each of the focal spots is an image of a laser spot on the retina. Moreover, for each cell of the raster this image is built by the rays passing through different parts of the pupil. Accordingly, any deviation from the ideal (planar) wavefront causes the hartmannogram spots to shift from the centers of the cells. By recording these displacements, one can reconstruct the wavefront shape and the aberration map using the least squares method. In the multispot - 250 aberrometer, the hartogram is recorded with a frequency of 30 Hz and a resolution of 640 × 480 pixels. The map of aberrations is restored in the form of 36 Zernike polynomials (aberrations up to 6th order inclusive). Zernike polynomials of the first order describe tilt (prism), second-order defocus and astigmatism, third-order coma and trefoil (trifoil), fourth-order spherical aberrations and fourth-order astigmatism. The root mean square (RMS) value of the wavefront errors from the ideal in the pupil plane of the optical system is a quantitative characteristic of the optical image quality. An optical system is considered good if the Zernike coefficients tend to zero. After carrying out aberrometric studies and obtaining a wavefront map, personalized ablation is calculated in the 6.0 mm area of the cornea using the original Analyse - 250 program. Moreover, when calculating, we introduced a 30% correction for increasing ablation for IV and V aberration orders. The value of this correction was established by us experimentally during corneal keratomileusis, which increases (induces) corneal aberrations of the fourth and fifth orders. After the calculations, we carry out the standard procedure M-Lasik using the calculated scan file of personalized ablation for aberrations of the I-V orders.

Example No. 1

Sick Derevenchin S.M., Amb. card number 152689, entered the Tambov branch of GU MNTK "Eye Microsurgery" named. Acad. S.N. Fedorova 11/17/04

Diagnosis: mild myopia, complex myopic astigmatism OU.

Vis OD: 0.1 sph - 1.0 cyl - 2.0 L 85 ° = 0.9

Vis OS: 0.2 sph - 1.0 cyl - 1.5 L 86 ° = 1.0

11/18/04, operation: personalized Lasik on Wavefront on OS.

Aberrometry results before surgery:

Zernike set

PV 15.4

RMS 3.6

II order (defocus): 3,752

Cylinder: 1,762

III order (coma): 0.108

IV order (sphere-like aberration): 0.462

V order: 0.508

The calculation of the operation is carried out according to the original program Analyse 250.

Zernike coefficients by software personification are translated into (μm) ablation and recorded in a scan file of a future operation, and when calculating the ablation for IV and V orders increases from the calculated one by 30%. As a result of the calculations, personalization of ablation in microns was obtained.

II order (defocus): 58.1 microns.

astigmatism: 23.1 microns.

III order (coma): 1.8 microns.

(trifoil): 1.7 μm.

IV and V orders of magnitude ablation increased by 30% of the calculated 2.1 microns (IV), 6.3 microns (V).

The result of the operation after 1 month.

Vis OS: 1.1

Aberrometry:

PV: 7.0

RMS: 1.3

II order - 0.2

Astigmatism - 0.7

III order - 0.06

IV order - 0.02

V order - 0.048

As a result, the aberration operations of the fourth and fifth orders approach 0! The square root of the sum of the squares of all deviations from the ideal wavefront (RMS), giving a qualitative characteristic of the severity of all aberrations, decreased by 2 times.

Example No. 2

Patient Shcherbakova N.E., Amb. card No. 152376, was admitted to the TF GU MNTK "Eye Microsurgery" from 11/13/04 with a diagnosis of weak myopia OU.

Vis OD: 0.06 sph - 2.5 cyl - 0.5 L 170 ° = 1.0

Vis OS: 0.06 sph - 2.0 cyl - 0.5 L 43 ° = 1.0

11.16.04 operation: personalized Lasik on Wavefront on OD.

Aberrometry results before surgery:

Zernike set:

RMS: 3.8

PV: 17.8

II order (defocus): 1.51

(astigmatism): 0.9

III order (coma): 1.0

(trifoil): 0.18

IV order: 0.83

V order: 0.12

The calculation of the operation, taking into account the increase in ablation of IV and V orders of magnitude by 30% in the 6.0 mm ablation zone (in microns).

II order (defocus): 69.4 microns

(astigmatism): 17.3 microns

III order (coma): 1.9 microns

(trifoil): 3.8 μm

IV order taking into account 30% correction - 1.5 microns

V order taking into account 30% correction - 6.2 microns

The results of the operation after 1 month:

Vis OD: 1.25

Aberrometry:

PV: 11.1

PMS: 1.5

Zernike set:

II order (defocus): 0.26

(astigmatism): 0.1

III order (coma): 0,043

(trifoil): 0.03

IV order: 0.23

V order: 0.08

Example No. 3

Patient Leonova V.P., amb. card No. 153129, was admitted to the TF GU MNTK “Eye Microsurgery” on December 1, 04 with a diagnosis of mild myopia, complex myopic astigmatism.

Vis OD: 0.05 sph - 2.5 cyl - 2.5 L 169 ° = 1.0

Vis OS: 0.05 sph - 3.0 cyl - 1.5 L 177 ° = 1.0

2.12.04 operation: personalized Lasik on Wavefront on OS.

Aberrometry results before surgery:

Zernike set:

RMS: 25.6

PV: 5.9

II order (defocus): 2.26

(astigmatism): 1.7

III order (coma): 0.18

(trifoil): 0.218

IV order: 0.334

V order: 0.278

The calculation of the operation, taking into account the increase in ablation of IV and V orders of magnitude by 30% in the 6.0 mm ablation zone (in microns).

II order (defocus): 81.9 μm

(astigmatism): 30.1 μm

III order (coma): 5.2 microns

(trifoil): 4.9 μm

IV order taking into account the 30% amendment - 0.9

V order taking into account the 30% correction - 4.5

The results of the operation after 1 month:

Vis OS: 1.15

Aberrometry:

PV: 8.8

PMS: 2.0

Zernike set:

II order (defocus): 0.13

(astigmatism): 0.33

III order (coma): 0.147

(trifoil): 0.012

IV order: 0.123

V order: 0.0115

Claims (1)

The method of performing the operation of personalized laser keratomileusis in the presence of higher order aberrations, which consists in determining aberrations by measuring the wavefront of the optical tract of the eye and performing ablation of the corneal stroma, characterized in that prior to the operation, personalized ablation is calculated and a 30th correction is introduced to increase the ablation for aberrations higher orders - 4th and 5th.