A NEW METHOD OF TREATING PROGRESSIVE KERATOCONUS BY FEMTOSECOND KERATOTOMY

The purpose of this study is to evaluate the results of experimental femtosecond radial keratotomy using Russian laser "Femto Visum" on the cadaver eye. The technical feasibility of this method, the quality of this procedure, and the histological structure of the preparation obtained from the cornea of the cadaveric eye were evaluated.

A method for the treatment of keratoconus I-III grade has been developed, the essence of which consists in applying 4-12 stromal corneal incisions using a femtosecond laser in the annular corneal zone with an external diameter of 8-11 mm, an internal diameter of 5-6. 5 mm; the length of the incisions is equal to the width of the annular zone, the depth of the incision is 75% of the thickness of the cornea in the incision application zone, with a distance from the anterior surface of the cornea of 60 microns. 

A femtosecond laser FemtoVisum was used to perform 8 radial incisions in the annular area of the cornea with an external diameter of 9.5 mm, internal 5.0 mm for the following parameters: wavelength 1030-1040 nm, pulse duration 300-400 fs, pulse repetition rate 1 MHz, pulse energy 0.75 mJ, focus spot size < 2 µm. The thickness of the cornea of the cadaveric eye was 900 µm. The distance from the anterior surface of the cornea was 60 µm. The depth of the incisions was 675 µm. Departure from the anterior corneal surface was necessary to assess the possibility of precise laser incision in the anterior corneal layers, which is necessary for future dissection of the Bowden's membrane with preservation of the epithelial layer integrity. The necessity of this step is due to the fact that until now, none of the foreign companies involved in the production of femtosecond lasers has been able to create software for conducting metered-dose, different in location, number and depth for the treatment of patients with keratoconus, as well as any other refractive operations, including in patients with myopia and thin cornea. After radial incisions were made on the eyes, a pentacam device was used to examine them. A total of 10 cadaveric eyes were operated on. 5 with an indentation of 60 µm from the surface. 5 without indentation with damage to the epithelium. 

Radially symmetrical equidistant incisions were successfully performed. The central and limbal corneal areas remained intact. There were no gas bubbles in the anterior chamber, which indirectly indicated the integrity of the descemet membrane.

According to the results of histology, the success of surgical intervention was revealed. The stroma was dissected to a predetermined depth, all the incisions remained an indent from the anterior surface of the cornea, and no corneal incision was observed in any of the incisions.

A new promising method for treating progressive keratoconus using a femtosecond laser, which has no analogues in the world, has been developed. The technical feasibility of this procedure is confirmed by experimental results and histological examination data.