RU2427357C1 - Method of treating post-operation induced astigmatism after implantation of intrastromal corneal segments in case of keratoconus - Google Patents

Abstract

FIELD: medicine. ^ SUBSTANCE: invention relates to medicine, in particular to ophthalmology, and can be used for treatment of keratoconus. 6 months after implantation of intrastromal corneal segments determined is optic axis of anterior surface of cornea with induces astigmatism, in 8-9 millimetre zone of cornea realised is non-through radial cut in two perpendicular meridians to the depth of implantation of intrastromal segments, layers of cornea stroma are separated in layers clockwise and counterclockwise, after which microsegments are installed, in region of cuts applied are sutures 10.0. Corneal microsegments with arch length 80-90 are installed. Thickness of microsegments is selected depending on value of spherical equivalent of refraction. ^ EFFECT: application of invention ensures correction of post-operation induced astigmatism from 2,5 to 10,0 D, prevents disease progressing. ^ 7 dwg, 1 ex

Description

The invention relates to medicine, in particular to ophthalmology, and can be used to treat keratoconus.

A known method of treating keratoconus in the initial and advanced stages of the disease by implantation of intrastromal corneal segments (Colin J, Velou S. Current surgical options for keratoconus. J. Cataract. Refract. Surgery 2003 Feb; No. 29. - Vol. - 2. - P: 379-386). The essence of the method lies in the fact that when implanting intrastromal corneal segments (IRS) into the peripheral part of the stroma, the radius of curvature of the front surface of the cornea changes, as a result of which the cornea is flattened from the periphery to the center. The achieved flattening is proportional to the thickness of the inserted implant, with increasing thickness of the segment, the distance between the layers of the cornea and the resulting flattening in the center increase.

The disadvantages of the method are the unpredictability of the refractive effect and, as a consequence, the development of postoperative induced astigmatism from 1.5 D to 11.00 D. This is due to the fact that the cornea is flattened precisely in the meridians where the segments are installed, and in the meridians where the segments absent, induced astigmatism of various degrees develops, which is not amenable to contact correction, which tends to increase during the postoperative period and leads to a significant decrease in patients' vision.

There is a method of surgical correction of induced astigmatism by the method of tangential keratotomy after cataract extraction, which allows to reduce the degree of astigmatism on average from 1.2 to 4.0 D (Fedorov I.S. Surgical correction of postoperative astigmatism in patients with IOLs. Diss. Ph.D. Medical Sciences . M., 1984, 123 S.), adopted as a prototype.

There are reports in the available literature (Miller K.M. Limbal arcuate keratotomy reduces up to 3 D of astigmatism. Ocular surgery News 1997; 15. - P.24) that such a technique is not effective enough and gives hypocorrection in 75% of cases. This is due to the fact that the authors' main operational access was projected in the weak meridian of the cornea and, therefore, a partial neutralization of the refractive effect of keratotomy incisions occurred. In accordance with published data, cases of under-correction during anterior keratotomy are 27.4 + 3.6%.

Keratotomy is an invasive operation in which the flattening of a small central area is achieved at too high cost through the stroma. Scars formed in their place remain the place of least resistance and cause a significant decrease in the strength of the outer capsule of the eye.

The predictability of the results of the operation was also insufficient due to the objective difficulties of drawing up an accurate program and the unpredictability of the scarring process. As a result of uneven scarring of the incisions, the cornea experiences uneven deformations leading to optical irregularities.

The objective of the invention is to develop an effective method for the treatment of induced astigmatism after implantation of intrastromal corneal segments with keratoconus.

EFFECT: correction of postoperative induced astigmatism from 2.5 to 10.0 D, prevention of disease progression.

The proposed method is as follows: 6 months after the standard implantation technique of the intrastromal corneal segments, using a keratotopograph (OPD-scan Nidek, Japan), refraction, keratometry, and corneal topography are determined. Then determine the optical axis of the anterior surface of the cornea with induced astigmatism. The thickness of each microsegment is selected depending on the spherical equivalent (SE) of refraction, calculated as the arithmetic average of the refraction of the two main meridians, namely: with SE from -2 to -4, the thickness of the segments is 150 μm, with SE from -4.1 to -6 the thickness of the segments is 200 microns, with SE from -6.1 to -8 the thickness of segments is 250 microns, with SE from -8.1 to -10 the thickness of segments is 300 microns, with SE from -10.1 to -12 the thickness of segments - 350 microns. The length of the arc of microsegments is 80-90 °. Then, in the 8-9 mm zone of the cornea (the microsegment implantation zone should be twice as large as the width of the installed segments, due to the fact that during implantation closer to the segments, stratification of the corneal stroma is possible, and closer to the limb the proper refractive effect will be insufficient) keratotomy knife carry out a non-through radial incision of the cornea in 2 perpendicular meridians to a given depth (depending on the previous implantation depth of the intrastromal segments). The layers of the corneal stroma are stratified clockwise and counterclockwise, then microsegments are installed in the formed bed, 10.0 sutures are applied in the incision area. Under the conjunctiva, 0.5 ml of a 0.1% dexazone solution is administered, a pressure dressing is applied.

The invention is illustrated by the following figures: figure 1 schematically shows a cornea with intrastromal corneal segments 1-2, axis 3, which often develops postoperative astigmatism; figure 2 - cornea with segments and implanted microsegments 4-5; figure 3 is a topographic map of a rabbit before implantation of intrastromal corneal segments; figure 4 is a topographic map of a rabbit with developed induced astigmatism; figure 5 is a topographic map of a rabbit after implantation of microsegments, and alignment of the front surface of the cornea; figure 6 - intrastromal segments established by the generally accepted standard method in the stroma of the rabbit cornea; Fig.7 - microsegment 6, installed by the proposed method, in the stroma of the rabbit cornea.

The advantage of this method in comparison with the prototype is that to compensate for induced astigmatism, the implementation of the plus-tissue technique is proposed, when implanting microsegments, induced astigmatism from 2.5 to 10.0 D is corrected. In addition, there are no non-perforating incisions that under the action of intraocular pressure can lead to the progression of the disease.

To compensate for pathological changes, it is proposed to carry out concentric partial stratification of the cornea in order to form plus tissue in the intervention zone.

Thus, the implantation of microsegments in the stroma of the cornea along the optical axis, in which postoperative induced astigmatism appeared, allows to achieve the indicated technical result, namely, to reduce its values, improve the visual functions of the eye, and reduce the risk of progression in the future disease.

Example: experimentally, implantation of intrastromal corneal segments of 160 ° and 200 μm in rabbit eyes was carried out according to the standard method (Dvali M.L., Tsintsadze N.A., Sirbiladze B.V., Gibradze K.A. Implantation of intrastromal corneal segments with keratoconus. Ophthalmology. 2006. No. 2, p. 5-8).

Data refractokeratometry before surgery:

OD sph cyl Oh 2.0 -1.25 3 ° R1 7.16 47.25 1 ° R2 7.05 47.75 91 ° ave 7.10 47.50 cyl -0.5 1 °

Data refractokeratometry after implantation of intrastromal corneal segments:

OD sph cyl ax -0.75 -10.25 163 ° R1 8.45 40.00 66 ° R2 6.72 50.25 156 ° ave 7.58 44.50 cyl -10.25 50 °

Thus, there is an increase in the values of induced astigmatism to 10.25 D along the 50 ° axis.

According to the proposed method, two intrastromal microsegments were implanted into an 8-9 mm zone of the cornea with a thickness of 200 μm and an arc length of 80 ° (the arc length of these microsegments is obtained by dividing the standard intrastromal corneal segment by an arc length of 160 ° into two parts, grinding its edge and the subsequent disinfection).

Refractokeratometry data after microsegmet implantation:

OD sph cyl ax -0.25 -2.50 163 ° R1 9.27 36.50 15 ° R2 8.59 39.25 105 ° ave 8.93 37.75 cyl -2.75 50 °

As can be seen from keratometry, induced astigmatism decreased from 10.25 D to 2.75 D, keratometry data decreased from 50.25 D to 39.25 D, which indicates a flattening and leveling of the front surface of the cornea.

Claims (1)

A method of treating induced astigmatism, characterized in that 6 months after implantation of the intrastromal corneal segments, the optical axis of the anterior surface of the cornea with induced astigmatism is determined, in the 8-9 mm area of the cornea, a non-through radial incision is made in two perpendicular meridians to form the depth of implantation of the intrastromal segments, bed, in which microsegments are installed, the arc length of which is 80-90 °, and the thickness of each is selected depending on the value of the spherical equivalent refractive index (SE), namely: with SE from -2 to -4, the thickness of the segments is 150 microns, with SE from -4.1 to -6 the thickness of segments is 200 microns, with SE from -6.1 to -8 the thickness of the segments is 250 microns, with SE from -8.1 to -10 the thickness of the segments is 300 microns, with SE from -10.1 to -12 the thickness of the segments is 350 microns.

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