RU2841923C1 - Method for banding therapeutic optical keratoplasty in keratoconus - Google Patents

Abstract

FIELD: medical science.

SUBSTANCE: invention refers to medicine, namely to ophthalmology, and aims at banding therapeutic optical keratoplasty in keratoconus. Intrastromal pocket is formed in the recipient's cornea. Donor layered corneal segment is placed therein. Femtosecond laser is used to dissect a donor corneal annular flap. Corneal segments made of polymethyl methacrylate are implanted therein at an arc length of 90 to 160 degrees depending on an astigmatism value and placed in an intrastromal recipient’s corneal pocket in parallel to a strong axis.

EFFECT: invention provides simultaneous arrest of disease progression and reduced level of corneal astigmatism.

1 cl, 3 ex

Description

The proposed invention relates to medicine, namely to ophthalmology, and is intended for performing bandage therapeutic optical keratoplasty for keratoconus.

Despite the existence of many methods of surgical treatment of keratoconus, improvement of surgical technique to improve refractive indices remains an urgent problem.

Implantation of corneal segments made of polymethylmethacrylate has found wide application in the treatment of initial keratoconus. This method was first proposed by J. Colin in 1997 for the correction of myopia. In 2000, the author implanted semi-rings for the first time in ten patients with keratoconus (Colin J., Cochener B., Savary G., Malet F. Correcting keratoconus with intracorneal rings. // J. Cataract Refract. Surg. - 2000. - Vol.26, №8. - P. 1117-1122). The obtained results indicated an increase in visual acuity. The essence of the operation consists in creating a framework in the weakened area of the cornea. Due to the achievement of flattening of ectasia in this area, corneal astigmatism decreases. This intervention is indicated for keratoconus in cases of the absence of central scars. In this case, the thickness of the cornea should be at least 400 µm at any point of its measurement. Both in the initial and late postoperative period, complications such as ring dislocation and ring eruption may occur. A possible cause of complications is the use of synthetic material that is not capable of forming a biological connection with the surrounding tissues, which, in turn, may be the reason for the lack of stabilization of the keratectasia process.

A method for treating keratoconus by intrastromal implantation of a ring segment is known. It was proposed by a group of authors from the M.M. Krasnov Research Institute of Eye Diseases in 2015 [Patent RU 2565485, 10/20/2015]. It consists in forming an intrastromal pocket in the cornea in the area of greatest thinning and protrusion and implanting a donor corneal ring segment into it with a thickness of 200 to 350 μm in accordance with the amount of astigmatism and a width of 1.5-2.5 mm in accordance with the size of the protrusion and a segment angle of 70-180°. The method strengthens the cornea in the ectasia area by increasing the thickness in the thinning area, which helps stabilize the progression of the disease. At the same time, due to the thickening of the peripheral part of the cornea, its paracentral zone flattens, which leads to improved optical properties and increased visual acuity. The method was called bandage therapeutic optical keratoplasty and was further developed (Patent RU 2742521, 08.02.21). However, despite the reduction in corneal deformation, the corneal surface remains irregular, which causes residual corneal astigmatism. Patent RU 2565485 is accepted as the closest analogue.

The objective of the invention is to develop a modified method of bandage therapeutic optical keratoplasty.

The technical result of the proposed method is the simultaneous stopping of the progression of the disease and the reduction of the level of corneal astigmatism.

The technical result is achieved by implanting a complex of donor cornea and corneal segments made of polymethyl methacrylate.

The method simultaneously strengthens the cornea in the ectasia zone, flattens its paracentral zone and increases its rigidity in the required meridians, which allows stabilizing the keratectasia process and reducing the degree of corneal astigmatism. In this case, the parameters of the thickness of the donor ring-shaped flap, which can vary depending on the degree of refraction of the cornea and the size of the axial length, its internal and external diameter, the diameter of the corneal segments correspond to those in the closest analogue. In this case, the angle of location can vary within 90-160° in accordance with the magnitude of astigmatism. The diameter and height of the corneal segments are standard for BLOCK (5 mm and 150 μm, respectively).

The interlamellar donor corneal flap allows to strengthen the recipient's cornea, and the corneal segments made of polymethyl methacrylate previously implanted in it - to level the surface of the deformed cornea due to their rigidity. Such a comprehensive approach ensures stabilization of the progression process and simultaneously improves visual acuity due to a decrease in the level of corneal astigmatism in comparison with the conventional method of bandage therapeutic optical keratoplasty.

The method was implemented on 12 patients. The observation period ranged from 1 to 12 months. In all cases, it was possible to stabilize the progression of the disease and reduce the level of corneal astigmatism.

The method is carried out as follows.

An intrastromal pocket is formed in the recipient's cornea. The donor corneal layered segment is placed in it. The donor corneal segment is preliminarily stratified using a femtolaser.

annular flap, the donor corneal annular flap is first stratified. Corneal segments made of polymethyl methacrylate with an arc length of 90 to 160 degrees are implanted into it, depending on the magnitude of astigmatism, and it is placed in the intrastromal pocket of the recipient's cornea parallel to the strong axis.

Clinical example 1.

Patient H., 38 years old, came with the diagnosis: OU - Keratoconus stage III. Visual acuity at OD=0.05 with sph. -8.5 D cyl -9.25 D ах 23°=0.3, at OS=0.1 with sph. -7.75 D cyl -8.0 D ах 157°=0.7. Corneal thickness at OD in the thinnest zone was 422 µm, at OS - 424 µm. Refractive indices in the central 3 mm zone at OD: K1 47.2, K2 54.4, Km 50.8, Astig 7.2 D, at OS: K1 47.0, K2 54.0, Km 50.4, Astig 7.0 D.

Bandage therapeutic optical keratoplasty (BOK) was performed on OD using a known method. After 1 week, visual acuity was 0.4 n/corr, and after 1 month - 0.5 n/corr. Keratometric indices 1 month after surgery: K1 43.6, K2 48.8, Km 46.2, Astig 5.2 D, Th 449 μm. Despite the increase in visual acuity after surgery, residual corneal astigmatism of 5.2 D remained. Taking into account the latter, a decision was made to perform a modified BOK on the other eye with implantation of a corneal segment in order to increase the rigidity of the transplant and smooth the corneal surface to reduce astigmatism to an even greater extent.

The operation on OS was performed using the described method. After local instillation anesthesia, an intrastromal pocket with an internal diameter of 3.4 mm and an external diameter of 9 mm was formed using a femtosecond laser. A ring-shaped flap 300 μm thick and 2.75 mm wide was cut out of the donor cornea, in the layers of which a pocket in the form of a ring 5 mm in diameter and 0.8 mm wide was formed. A corneal segment 5 mm in diameter, 150 μm high and 120° arc length was implanted into the resulting pocket. The formed complex of the donor cornea and the corneal segment was implanted into the previously prepared intrastromal pocket.

The postoperative period was uneventful. On the first day after the operation, slight local edema of the cornea and transplant was noted. After 1 week, visual acuity on OS was 0.7 n/corr, after 1 month - 0.8 n/corr. Keratometric data 1 month after the operation: K1 39.2, K2 41.3, Km 40.2, Astig 2.1 D, Th 456 μm, which indicates smoothing of the corneal surface, and therefore a greater reduction in corneal astigmatism compared to BLOCK without implantation of corneal segments.

Clinical example 2.

Patient S., 34 years old, was admitted with the following diagnosis: OD - Keratoconus stage II-III. OS - Keratoconus stage I. Condition after crosslinking. Visual acuity at OD=0.07 with sph. -7.5 D cyl -4.5 D ах 79°=0.3, OS=0.7 with cyl -3.0 D ax 110°=1.0. At OD, the corneal thickness in the thinnest zone was 429 µm, refractive indices in the central 3 mm zone: K1 42.3, K2 47.4, Km 44.8, Astig 5.1 D.

The operation on OD was performed using the described method. After local instillation anesthesia, an intrastromal pocket with an internal diameter of 3.4 mm and an external diameter of 9 mm was formed using a femtosecond laser. A ring-shaped flap 280 μm thick and 2.75 mm wide was cut out of the donor cornea, in the layers of which a pocket in the form of a ring 5 mm in diameter and 0.8 mm wide was formed. A corneal segment 5 mm in diameter and 150 μm high with an arc length of 90° was implanted into the resulting pocket. The formed complex of the donor cornea and the corneal segment was implanted into the previously prepared intrastromal pocket.

The postoperative period was uneventful. After 1 week, visual acuity was 0.65 n/corr, after 1 month - 0.7 n/corr. Keratometric data 1 month after the operation: K1 41.3, K2 44.0, Km 42.6, Astig 2.7 D, Th 463 µm.

Clinical example 3.

Patient P., 29 years old, came with the diagnosis: OD - Keratoconus stage II-III. OS - Suspected keratoconus. Visual acuity at OD=0.1 with sph. -3.5 D cyl -9.5 D ах 88°=0.4, OS=0.9 n/corr. At OD, the corneal thickness in the thinnest zone was 431 μm, refractive indices in the central 3 mm zone: K1 43.9, K2 53.4, Km 48.6, Astig 9.5 diopters.

A modified BLOCK with implantation of a corneal segment was performed at OD. After local instillation anesthesia, an intrastromal pocket with an internal diameter of 3.4 mm and an external diameter of 9 mm was formed using a femtosecond laser. A ring-shaped flap 280 μm thick and 2.75 mm wide was cut out of the donor cornea, in the layers of which a pocket in the form of a ring 5 mm in diameter and 0.8 mm wide was formed. Corneal segments 5 mm in diameter, 150 μm high and 160° arc length were implanted into the resulting pocket. The prepared complex of the donor cornea and corneal segment was implanted into the previously formed intrastromal pocket.

The postoperative period was uneventful. After 1 week, visual acuity was 0.45 n/corr, after 1 month - 0.65 n/corr. Keratometric data 1 month after the operation: K1 38.3, K2 41.5, Km 39.9, Astig 3.2 D, Th 479 µm.

Thus, the method of modified bandage therapeutic optical keratoplasty provides better refractive indices and visual acuity, which allows its use in further clinical practice.

Claims (1)

A method for performing bandage therapeutic optical keratoplasty for keratoconus, including the formation of an intrastromal pocket in the recipient's cornea and the placement of a donor layered corneal ring segment in it, characterized in that a donor corneal ring-shaped flap is preliminarily stratified using a femtolaser, corneal segments made of polymethyl methacrylate with an arc length of 90 to 160 degrees are implanted into it depending on the magnitude of astigmatism and it is placed in the intrastromal pocket of the recipient's cornea parallel to the strong axis.