Mathematical modeling of the refractive effect of SMILE surgery in high degree myopia correction

The aim of the study. To develop a mathematical model of changes in corneal refraction during femtosecond laser-assisted lenticule extraction through a small surgical incision and, on this basis, to propose a technology for modified calculation of surgical parameters and to prove its effectiveness. Material and methods. The study included 191 patients with high myopia. They were divided into two groups: group  1 consisted of 55  patients who  were  had  SMILE (SMall Incision Lenticule Extraction) surgery with standard calculations; group  2 included 136 patients who had SMILE surgery with a modified calculation of surgical parameters based on the developed mathematical model of the refractive effect of the surgery. Results. When assessing the refractive effect of patients who were operated using standard technology, it was found that it was possible to achieve a refraction different from emmetropia for ± 0.5 D only in 51 % of cases; in the remaining patients, the planned residual refractive effect was obtained and averaged –1.96 ± 0.29 D. In patients operated using the modified technology, a statistically significantly better refractive result was achieved already on the first day. A refractive error of more than ± 1.0 D was obtained in only 1 % of cases; a deviation from the calculated refraction of ± 0.5 D was achieved in 82 % of cases, with the average values by 1 year –0.24 ± 0.57 D. Conclusions. The developed technology of a modified calculation of the parameters of the SMILE surgery for high myopia correction makes it possible to obtain an optimal refractive effect in compliance with safety rules when the structural and functional parameters of the eye are initially unfavorable for refractive surgery

Features of Femtosecond Correction of High Myopia through Small Access

Aim. To modify the calculated parameters of the lenticle extraction refractive surgery through a small access (SMILE), evaluate its safety and clinical efficacy in correcting high myopia.Materials and methods. 34 patients (68 eyes) underwent surgery by a modified SMILE technology under local anesthesia. In all cases, the patients had a high degree of myopia, in 37 % in combination with astigmatism.Uncorrected visual acuity before surgery averaged 0.05 ± 0.11, best corrected visual acuity of 0.94 ± 0.1, the pre-operative spherical refraction component was –7.23 ± 0.75, the cylindrical component was –0.48 ± 0.59.During the operation, to obtain the maximum possible refraction result using the proposed method, the standard operation parameters were changed: the corneal flap thickness was reduced to 100 μm, the neural optical layer by 5 μm, the diameter of the optical zone depended on the residual cornea thickness, which should exceed 280–290 μm. Corneal access was increased by 15–20 degrees.Results. The next day after surgery, monocular uncorrected visual acuity in distance in 73 % of patients was 0.8 or higher, and in 41 % of cases it was equal to or exceeded 1.0. The spherical equivalent on the first day after surgery had a slight hypermetropic shift, which was completely leveled by the year of follow-up. During the surgical intervention and in the postoperative period, no complications were noted.Conclusion. Using the proposed algorithm for calculating the refractive effect of the operation SMILE with a high degree of myopia allows obtaining a high refractive effect and avoiding possible complications

CHARACTERISTICS OF PROLIFERATION AND INTERCELLULAR ADHESION IN PRE-CANCEROUS AND MALIGNANT EPITHELIAL SKIN TUMORS

Background: Differential diagnostics between actinic keratosis which is one of pre-cancerous skin diseases, and intra-epidermal squamous cell skin cancer (or Bowen's disease) could be difficult in some cases even with morphological examination. The study on molecular characteristics of pre-cancerous skin disorders would allow for more accurate diagnostics and assessment of prognosis. Aim: To study proliferative activity of keratinocytes and E-cadherin expression on cell membranes in actinic keratosis and in Bowen's disease, with identification of differential diagnostic criteria. Materials and methods: We performed an immunohistochemistry study with anti-Ki-67 and anti-Е-cadherin monoclonal antibodies in skin bioptates of 23 patients with actinic keratosis and 10 patients with Bowen's disease. Results: The mean proliferation index in actinic keratosis without the bowen-like loci was 30.9 ± 11.4% (range, from 11.5 to 48.4%), and in actinic keratosis with the bowen-like loci, 40.3 ± 8.6% (range, from 31 to 57.6%). In both groups, E-cadherin expression in all cases (100%) was located in cell membranes. The mean proliferation index in Bowen's disease was 44.7 ± 8.2% (range, from 33.3 to 60%). In 48.2% of Bowen cells, abnormal type of E-cadherin expression (reduced membranous, membranous and cytoplasmatic and cytoplasmatic only). Conclusion: Actinic keratosis and Bowen's disease represent different stages of one and the same malignant process that have different proliferative cell activity and E-cadherin expression, which could be used as differential diagnostic markers

PREOPERATIVE ASSESSMENT OF THE INITIAL CONDITION OF THE EYE SURFACE IN PATIENTS WITH MYOPIA

The purpose is to assess the structural state of the cornea and pre-corneal lacrimal film in patients with myopia before refractive surgery, to identify the relationship with changes in cytokine concentration in the tear. Material and methods. 62 patients (124 eyes) with myopia were examined. The first group included 26 patients, only glasses were used for the correction of myopia, and in the 2nd group, 36 patients who used soft contact lenses during 5 to 15 years. Methods of examination: determination of the thickness of the corneal epithelium, height and width of the lacrimal meniscus, assessment of the biomechanical properties of the cornea, the Norn and Schirmer tests. Content of cytokines in the tear – interleukin 10 and tumor necrosis factor α – was measured using the test set «BEST» by enzyme immunoassay. Results. The decrease in the thickness of the epithelium of the cornea, the height and width of the lacrimal meniscus, the stability of the tear film, and the ratio of interleukin-10 to the tumor-α necrosis factor in patients who use contact lenses for a long time are revealed. The conclusion. Prolonged wearing of contact lenses for correction of myopia is accompanied by signs of symptomatic dry eye syndrome against a background of moderate oppression of the anti-inflammatory activity of tears

An integrated approach to the second correction of residual myopia after extraction of lenticula through a small access

Purpose. To develop a new method for correction of residual myopia after the Smile surgery, to evaluate a functional effect of this type of surgical intervention. Material and methods. The study included patients with mild residual myopia after the Smile surgery, who were corrected for insufficient refractive effect using photorefractive keratectomy (PRK), CIRCLE and the original SPS technique (Smile post Smile). In order to assess changes in the parameters of the cornea and visual functions, a profound ophthalmological examination was performed before and after the operation with a multiplicity of 1 day and 6 months. Results. All patients had a good refractive and functional effect by six months after surgery, and the maximum increase in visual acuity was achieved already on the first day after CIRCLE and SPS. The highest satisfaction with the quality of vision was revealed in patients after SPS surgery. Conclusion. The results obtained after the correction of residual myopia by the SPS method (Smile post Smile) indicate that the developed technology is highly effective, safe and can be recommended for application in the clinical practice

Relex Smile and its features for the correction of high degree myopia

Purpose: to modify the calculated parameters of the refractive operation - extraction of the lenticle through small access (Smile), evaluate its safety and clinical effectiveness in correcting high-grade myopia. Material and methods. 34 patients (68 eyes) were operated by the modified Smile technology under local anesthesia. In all cases, patients had a high degree of myopia, in 37 % - in combination with astigmatism. Uncorrected visual acuity before surgery was on average 0.05 ± 0.11, Best corrected visual acuity was 0.94 ± 0.1, preoperative spherical refractive component -7.23 ± 0.75, cylindrical component -0.48 ± 0.59. During the surgery, in order to obtain the maximum possible refractive result according to the proposed method (patent No. 2018113414 of April 13, 2013), the standard parameters of the operation were changed: the thickness of the corneal flap was reduced to 100 μm, the neutral optical layer was 5 μm, the diameter of the optical zone depended on the residual thickness of the cornea, which should exceed 290 microns. The increase in corneal access was 15-20 degrees. Results. During the surgical intervention and in the postoperative period there were no complications. The next day after surgery, monocular uncorrected visual acuity in the distance in 73 % of patients was 0.8 and above, and in 41 % of cases it was equal to or exceeded 1.0. The spherical equivalent in the first day after the operation had a small hypermetropic shift, which was completely leveled by the year of observation. Conclusion. Using the proposed algorithm for calculating the refractive effect of the SMILE operation in high degree myopia allows obtaining a high refractive effect and avoiding possible complications