[Current possibilities for the diagnosis and treatment of pterygium]. / Sovremennye vozmozhnosti diagnostiki i lecheniya pterigiuma.

Pterygium is a common inflammatory-proliferative disease characterized by the invasion of degeneratively altered fibrovascular tissue into the cornea. This literature review analyzes the etiological factors and pathogenetic concepts of its development, describes modern methods of diagnostics and surgical treatment of pterygium, and pays particular attention to the assessment of structural and functional changes in the cornea occurring during the growth of pterygium and after its excision.

[Modern techniques and features of selective keratoplasty]. / Sovremennye tekhnologii i vozmozhnosti selektivnoi keratoplastiki.

Selective keratoplasty involves replacing the affected layers of the cornea with similar donor tissue. In case of pathological changes in the middle and posterior stroma, deep anterior lamellar keratoplasty (DALK) is performed. Chronic corneal edema caused by endothelial dysfunction is an indication for endothelial keratoplasty - Descemet membrane endothelial keratoplasty (DMEK) or Descemet Stripping Endothelial Keratoplasty (DSAEK). Compared to penetrating keratoplasty (PK), these operations are characterized by a low risk of damage to intraocular structures and a relatively short rehabilitation period. Complications of selective keratoplasty include the formation of a false chamber between the lamellar graft and the recipient's cornea, ocular hypertension during anterior chamber air tamponade. Persistent epithelial defect can be a sign of primary graft failure in DALK, DSAEK and DMEK. Selective keratoplasty is characterized by a lower incidence of immune rejection than PK. In some cases, DALK can be complicated by corneal changes related to suture fixation of the graft. Long-term postoperative use of topical glucocorticoids can cause ocular hypertension and cataracts.

[Corneal changes in Fuchs endothelial corneal dystrophy and bullous keratopathy]. / Izmeneniya rogovitsy pri endotelial'noi distrofii Fuksa i vtorichnoi bulleznoi keratopatii.

OBJECTIVE: Evaluation of structural and immunohistochemical features of cornea in Fuchs endothelial corneal dystrophy (FECD) and bullous keratopathy (BK). MATERIAL AND METHODS: Group 1 - 44 patients (46 eyes) with FECD, group 2 - 42 patients (42 eyes) with BK. All patients underwent keratoplasty. Preoperative anterior segment optical coherence tomography (AS-OCT, RTVue-100, Optovue, USA) was performed. Endothelium-Descemet membrane (EDM) complexes, corneal buttons were obtained intraoperatively. Morphological (H&E staining) and immunohistochemical (primary antibodies to pancytokeratin, vimentin, fibronectin) studies were performed at the light microscope level (Leica DM-2500, Leica Application Suite V4.8, Leica Microsystems, Switzerland). RESULTS: A direct correlation is found between the results of DM analysis in vivo with OCT and ex vivo with light microscopy. DM thickness (AS-OCT) was significantly greater in FECD (23.0 [19.0; 27.0] µm), than in BK (13.0 [12.0; 14.0] µm). Morphological study of EDM and corneal buttons showed similar difference in DM thickness: 17.9 [16.1; 20.0] µm in FECD and 11.9 [11.3; 13.0] µm in BK. Irregular optical density of stroma is a feature of edema and local fibrosis. In FECD and BK pancytokeratin is expressed in epithelial and endothelial cells, vimentin - in keratocytes, macrophages and vascular endothelium, fibronectin - in DM. In FECD, vimentin is expressed in endothelial cells. CONCLUSION: FECD and BK are associated with different DM' and endothelium' abnormalities, which lead to similar changes of stroma and epithelium. AS-OCT is a useful method of FECD and BK in vivo diagnostics and the selection of treatment option.

[Deep anterior lamellar keratoplasty in extrusion of an incomplete intrastromal corneal ring segment (clinical observation)]. / Glubokaya perednyaya posloinaya keratoplastika pri ekstruzii nepolnogo intrastromal'nogo kol'tsa (klinicheskoe nablyudenie).

Intrastromal corneal ring segments (ICRS) of in various shapes are used to correct structural changes in the cornea and improve visual acuity in keratoconus (KC). The most serious complications of the technology infection, vascular ingrowth, and extrusion. In this study a 44-year-old patient underwent deep anterior lamellar keratoplasty (DALK) 5 years after implantation of ICRS in the shape of an incomplete ring to treat its extrusion of up to 30%, vascular ingrowth into the cornea and corneal syndrome. The following DALK technique was used: excision of the free part of the corneal segment, removal of the remaining part of the corneal segment, excision of 80% of thickness of the corneal block with a 8.5-mm trepan, pneumatic dissection of the stroma down to the Descemet membrane (DM), removal of the remaining stroma on the viscoelastic pillow, laying and suture fixation of the donor graft. There were no complications during the postoperative period, the graft remained transparent for up to 10 months. Uncorrected visual acuity (UCVA) increased from 0.01 to 0.4, best corrected visual acuity (BCVA) increased from 0.3 to 0.7. The number of endothelial cells decreased from 2980 to 2670 cells/mm2 (10.4%). This clinical case demonstrates that DALK surgery can be a reliable method of patient rehabilitation in cases of extrusion of ICRS in the shape of an incomplete ring and vascular ingrowth.

[Salzmann nodular degeneration: pathogenesis, clinical characteristics and treatment]. / Uzelkovaya degeneratsiya Zal'tsmana: osobennosti patogeneza, klinicheskoi kartiny i lecheniya.

Salzmann nodular degeneration (SND) is a rare non-inflammatory disease observed primarily in middle-aged women. The disease generally occurs in patients with chronic inflammation of the anterior ocular surface. Its etiopathogenesis remains poorly investigated. This literature review describes clinical manifestations, risk factors and diagnostic methods, evaluates the effectiveness of different therapeutic and surgical treatment methods. Understanding of the pathogenetic mechanisms, precise diagnosis and identification of the risk factors can help clinical physicians make the optimal choice of treatment strategy and achieve the best clinical outcomes.

[Opto-functional results in keratoconus patients after intrastromal keratoplasty]. / Optiko-funktsional'nye rezul'taty posle intrastromal'noi keratoplastiki pri keratokonuse.

Intrastromal keratoplasty with allograft implantation can stop the progression of keratoconus (KC) and improve visual acuity (VA). Although optimization of keratometric parameters and an increase in VA improve the quality of vision (QoV), there are other indicators that affect the QoV and the quality of life (QoL) of patients and require further study. PURPOSE: Analysis of quantitative and qualitative characteristics of vision in patients with stage II and III keratoconus who underwent intrastromal allokeratoplasty. MATERIAL AND METHODS: The study included 15 patients (15 eyes) with stage II-III KC (Amsler-Krumeich classification) aged 17 to 38 years old (28.8±6.2). All patients underwent intrastromal keratoplasty with implantation of an allograft in the form of a wide incomplete ring. The following parameters were assessed before and 6 months after surgery: distance VA with and without correction, near VA with and without correction, VA with glare effect, high-order aberrations (HOA), thickness of the tear film lipid layer, spatial contrast sensitivity (SCS) under photopic and mesopic conditions with light filters, reading speed. RESULTS: VA without correction increased from 0.15 to 0.7; with correction from 0.35 to 0.7. The glare effect with varying degrees of illumination did not affect VA either before or after surgery. Statistically significant changes were observed when comparing the aberrations «coma¼, «spherical¼, «trefoil¼ before and after the intervention, they became inverted. The thickness of the tear film lipid layer did not change significantly when comparing pre- and postoperative data. The use of light filters (orange, yellow) did not lead to significant changes in the VA and SCS under photopic and mesopic conditions. CONCLUSION: The use of a wide intrastromal allograft to correct deformity and stabilize the cornea in keratoconus improves the patients' quality of vision and visual performance.

[Long-term outcomes of bandage therapeutic-optical keratoplasty in the treatment of keratoconus]. / Otdalennye rezul'taty bandazhnoi lechebno-opticheskoi keratoplastiki pri lechenii progressiruyushchego keratokonusa.

Intrastromal keratoplasty has recently been widely used in the surgical treatment of keratoconus (KC). In 2013, a new type of interlamellar keratoplasty operation was developed - bandage therapeutic-optical keratoplasty (BTOK). PURPOSE: Evaluation of the long-term outcomes of surgical treatment of stages II and III progressive KC with BTOK technique. MATERIAL AND METHODS: The study included 107 patients (126 eyes): group 1 with stage II KC - 78 eyes, 100% of these patients were observed for 1 year, 52 eyes (66%) for 3 years, and 18 eyes (23%) for 5 years; group 2 - 48 eyes with stage III KC, with 100% of them observed for 1 year, 39 eyes (81%) for 3 years, and 12 eyes (25%) - 5 years. All patients received a customized allograft in the form of an intrastromal corneal ring segment (ICRS). RESULTS: During the first year after BTOK surgery, the uncorrected and corrected visual acuity (UCVA and CVA) in the first group increased by 0.5±0.04 (p<0.05) and 0.2±0.02 (p<0.05), respectively, in the second group - by 0.46±0.05 (p<0.05) and 0.47±0.05 (p<0.05) due to a decrease in refractive indices in the central 3.0 mm zone. In the first group, mean refraction in the central 3.0 mm zone (Km) was within 45±3.75 (p<0.05), in the second - 48.63±.2 diopters (p<0.05), while maximum refraction in the central 3.0 mm zone (Kmax) decreased from 50.02±2.20 (p<0.05) to 44.61±1.03 diopters (p<0.05) in the first group, from 58.21±3.43 (p<0.05) to 50.45±3.46 diopters (p<0.05) in the second group. The values of UCVA, CVA and refractive indices of the central corneal zone in the first and second groups did not change statistically significantly after three and five years. Minimum corneal thickness in the first group increased from 476.23±13.35 to 485.08±15.80 µm (p<0.05), in the second - from 412.73±38.63 to 422.00±42.25 µm (p<0.05). CONCLUSION: BTOK surgery can be used in patients with stages II and III KC to improve the visual functions, strengthen the ectatic cornea and stop the progression of the disease.

[Changes in the quality of vision after intrastromal allokeratoplasty for keratoconus (clinical observation)]. / Izmenenie kachestva zreniya posle intrastromal'noi allokeratoplastiki po povodu keratokonusa (klinicheskoe nablyudenie).

Scleral lenses, corneal collagen crosslinking, corneal implants and deep anterior keratoplasty are used to correct deforming changes in the cornea at advanced stages of keratoconus, which improves the quality of vision (QoV). The article presents an analysis of changes in QoV in a 30-year-old patient with stage III keratoconus who underwent intracorneal implantation of an allograft with a width of 2.75 mm and thickness of 300 µm at a depth of 370 µm. The following parameters were measured before and 6 months after the procedure: uncorrected visual acuity (UCVA), best-corrected visual acuity (BCVA), VA with glare, higher order aberrations (HOA), thickness of the lipid layer of the tear film, spatial contrast sensitivity, visual productivity. Observation results show that the Kmax index decreased from 55.9 D to 48.0 D, Kmin - from 39.8 D to 39.4 D, UCVA increased from 0.1 to 0.8 and BCVA - from 0.35 to 0.8. Thickness of the lipid layer of the tear film remained the same. The glare effect with different degrees of brightness did not affect visual acuity. Spatial contrast sensitivity in photopic conditions at medium frequencies increased from 19 to 37 dB, at high frequencies from - 0.5 to 22.5 dB, in mesopic conditions at medium frequencies from 11 to 28 dB, at high frequencies from - 0.5 to 12 dB. The «coma¼ and «spherical¼ aberrations decreased by 2 and 3 times, respectively, while «trefoil¼ increased by 3 times. Visual productivity increased by 36.8%. It may be concluded that the use of a wide intrastromal allograft in keratoconus improves the patient's visual quality and visual productivity. At the same time, the «vignetting¼ effect from the graft side is negligible in photopic conditions and is significant in mesopic conditions.

[On the tactics for surgical treatment of keratoconus in significantly altered corneal thickness]. / K voprosu o taktike khirurgicheskogo lecheniya keratokonusa pri sushchestvennykh izmeneniyakh tolshchiny rogovitsy.

PURPOSE: To evaluate the clinical and functional outcomes of bandage therapeutic-optical keratoplasty (BTOK) surgery in patients with keratoconus (KC) and significant changes in corneal thickness. MATERIAL AND METHODS: Surgical treatment was performed in 15 patients (15 eyes) with stage IV KC aged from 22 to 51 years (mean age - 32.61±7.94 years). The follow-up period lasted 3 years. All patients underwent BTOK surgery using an interlamellar graft with a thickness of 320 to 350 µm. RESULTS: Uncorrected and best corrected visual acuity increased in all patients after BTOK surgery and did not change statistically significantly during the entire follow-up period (3 years), amounting to 0.47±0.12 and 0.53±0.13, respectively. Keratometric parameters also remained stable by that observation time point and amounted to: Kmax - 53.01±2.30 D; Kmin - 41.63±2.24 D; Km - 47.32±1.91 D. CONCLUSION: The BTOK surgery helps achieve long-term (3 years) visual, optical and strengthening outcomes in stage IV KC patients when the use of other known techniques (corneal collagen crosslinking, corneal segments) is technically impossible because of the risk of complications due to significantly thinned cornea (less than 400 µm).

[Experimental studies of the biomechanical properties of the cornea]. / Eksperimental'nye issledovaniya biomekhanicheskikh svoistv rogovitsy.

The review presents the results of experimental studies of the biomechanical properties of the cornea. Selective evaluation of the individual corneal structures (for example, limiting membranes) using classical mechanical tests is to a certain extent limited due to the rather small thickness of these structures and the related difficulties in sample fixation. In real practice, the use of a method better adapted for conducting such studies - atomic force microscopy (AFM) - remains promising, since on the one hand it eliminates the need for mechanical capture and retention of the sample, and on the other - provides the capability for studying its segments separately.

[On the issue of allocating the pre-Descemet's layer in the corneal structure]. / K voprosu o vydelenii predestsemetovogo sloya v strukture rogovitsy.

Selective keratoplasty is known to be based on surgical manipulations aimed at dosed isolation of layered grafts in the corneas of the donor and the recipient. Some technological features of obtaining transplants have served as the basis for expanding the understanding of the corneal structure. Thus, analysis of the process of corneal stroma pneumodissection for isolation of the Descemet's membrane led to a suggestion that there was another layer in the cornea, it was designated as the pre-Descemet's layer. This article discusses the practicability of separating the pre-Descemet's layer from the perspective of structural, functional and surgical anatomy.

[Comparative assessment of the quality of life of keratoconus patients before and after intrastromal keratoplasty]. / Sravnitel'naya otsenka kachestva zhizni do i posle intrastromal'noi keratoplastiki pri keratokonuse.

Surgical treatment of keratectasia, in addition to its cessation, is aimed at increasing the acuity and quality of vision. This can also significantly affect patient's quality of life. The criteria for assessing the quality of life does not always consider the balance between quantitative indicators and subjective perception, which can depend on the psychological aspect of self-esteem.Purpose - to perform comparative assessment of the quality of life of patients with keratoconus (KK) before and after intrastromal keratoplasty by a newly developed method using an original questionnaire. MATERIAL AND METHODS: The study included 20 patients (14 men and 6 women, with mean age of 33 years, from 21 to 45 years old; 20 eyes) diagnosed with degree II-IV KK, with non-corrected visual acuity of 0.3 or lower. The original questionnaire with three blocks of questions about subjective assessment of the severity of discomfort associated with the disease, expectations of treatment results and its effectiveness was used to study the quality of life of KK patients who underwent surgery. The evaluation method used a five-point grading scale. RESULTS: Despite the inability to objectively assess the result of treatment, patients can generally note the trend for improvement. Especially significant are the increase of visual acuity, improvement of general health, feeling of comfort and more optimistic view of one's future. Comparison of the expectations and treatment results has shown that some therapeutic effects are overestimated by the patients, while some others are underestimated. A priori, they overvalue the effects of treatment (actions associated with visual tasks - reading, writing), but at the same time undervalue the characteristics of overall personal and emotional state (except for spatial safety and comfort), i.e. the characteristics that determine the quality of life. CONCLUSION: The aims of writing a valid and reliable questionnaire have been achieved partially, and its further development requires comparison of the obtained results with psychodiagnostic data, which would reveal the nature of psychological factors that form the quality of life perception in patients with various vision disorders.

[Results of confocal microscopy of the cornea after bandage therapeutic-optical keratoplasty in keratoconus]. / Rezul'taty konfokal'noi mikroskopii rogovitsy posle bandazhnoi lechebno-opticheskoi keratoplastiki pri keratokonuse.

Bandage therapeutic-optical keratoplasty (BTOK) is one of the modern methods of surgical treatment of keratoconus (KC) that allows to improve visual functions by changing keratotopographic and pachymetric parameters of the cornea in the zone of ectasia. Long-term results show that changes also affect the central part of the cornea, which tends to flatten. PURPOSE: To compare the light confocal microscopy appearance of the cornea before and after BTOK surgery. MATERIAL AND METHODS: We examined 15 patients (15 eyes) with progressive keratoconus (7 eyes with Amsler stage I KC and 8 eyes with Amsler stage III KC), who subsequently underwent BTOCK surgery. Using the Confoscan-4 confocal light microscope (Nidek, Japan), we studied the structure of central and paracentral cornea. The exact zone of interest was determined individually depending on the location of the graft. RESULTS: In all cases, morphological changes in the cornea characteristic of the stage II and III KC were detected. Twelve months after the operation, there was an increase in the transparency of intercellular substance of the stroma with a clearer visualization of keratocyte nuclei in the optical zone as well as at the site of the graft. In the area of interface, tissue compaction in the form of diffuse fibrosis with local scar formation could be seen. Neither significant changes in the cell structure, nor a decrease in cell density were found in the central part of ectasia and the areas of clear visualization of the endothelium under the graft. Additional postoperative assessment of the level of corneal light scattering indicated a tendency towards restoration of stromal transparency and optical uniformity. CONCLUSION: As a result of interlayer graft implantation in the zone of corneal ectasia, a tendency to structural improvement in its central and paracentral parts was revealed. Local fibrosis in the interface area can indirectly indicate biomechanical «strengthening¼ of this zone.

[Methods of surgical treatment of keratectasia and analysis of postsurgical quality of vision]. / Metody khirurgicheskogo lecheniya keratektazii i analiz posleoperatsionnogo kachestva zreniya.

Keratectasias are non-inflammatory dystrophic diseases of the cornea characterized by progressive bilateral thinning of the cornea that lead to deterioration in the quantitative and qualitative characteristics of vision reducing patient's quality of life. The changes can be asymmetrical and destructive. A number of surgeries have been proposed to reduce the negative effects of keratectasia including penetrating keratoplasty and its modifications, implantation of corneal ring segments, corneal cross-linking - alone and in combination with other methods, intrastromal keratoplasty. These methods can improve visual acuity to a certain degree and help slow the progression of keratectasia. This article studies various surgical methods used for treating keratectasia and analyses possible assessment of the quality of vision before and after the treatment.

[Bandage lamellar-optical keratoplasty for post-excimer laser keratectasia]. / Bandazhnaia lechebno-opticheskaia keratoplastika v lechenii iatrogennoi keratéktazii.

INTRODUCTION: According to various sources, occurrence rate of keratectasia (KE) after Laser in situ Keratomileusis (LASIK) ranges from 0.04 to 0.2%. No known technique for keratorefractive surgery eliminates the probability. Neither corneal cross-linking, nor implantation of polymeric segments can completely prevent its development. PURPOSE: To treat KE after LASIK with bandage lamellar-optical keratoplasty (BLOK) surgery and to evaluate the results. MATERIAL AND METHODS: The study included 22 patients with KE after LASIK divided into two groups. The first group consisted of 6 patients; they underwent BLOK surgery using a segment transplant 1.5 mm in width and 180-220 µm in thickness. The second group included 16 patients who underwent BLOK surgery using 2.75 mm wide, 290-350 µm thick allogeneic transplant of individual length. The follow-up lasted 4 years. RESULTS: In the first group, uncorrected visual acuity (UCVA) improved by 0.4±007, in the second group - by 0.46±0.15. After two years, two patients had their transplant exchanged for a wider one due to ectasia progression. Corneal refraction was stable at 45.36±1.47 Diopters in all other patients of the first group. In the second group, it was consistently between 40.6 and 45.7 Diopters. The main complication of the BLOK surgery was displacement of the edge of the corneal flap formed during LASIK - occurred in 4 patients. CONCLUSION: Bandage lamellar-optical keratoplasty proved effective in treating patients with KE after LASIK, leading to improvement of visual acuity, strengthening of the cornea and normalization of its surface; it slows further progression of ectasia.

[Modern methods of surgical treatment of keratectasias]. / Sovremennye khirurgicheskie metody lecheniia keratéktazii.

Keratectasia (KE) ranks as one of the main causes of impaired vision. The pathology is characterized by progressive thinning of the cornea, which causes its deformation, the appearance of irregular astigmatism, and the reduction of vision acuity. The article reviews modern surgical methods that can be used to prevent the progression and treat various types of KE.

[Bandage keratoplasty therapeutic-optical in treatment of progressing pellucid marginal corneal degeneration (a preliminary report)]. / Bandazhnaia lechebno-opticheskaia keratoplastika pri progressiruiushchei pelliutsidnoi marginal'noi degeneratsii rogovitsy (predvaritel'noe soobshchenie).

PURPOSE: To provide preliminary estimation of the effectiveness of bandage therapeutic-optical keratoplasty (BTOK; previously called inralamellar bandage keratoplasty) in patients with pellucid marginal corneal degeneration (PMD). MATERIAL AND METHODS: The study included 7 patients (8 eyes) with PMD aged 35 to 55 years operated with intralamellar bandage keratoplasty, the follow-up period comprised 3, 6, and 12 months after the surgery. RESULTS: All patients with PMD operated with intralamellar bandage keratoplasty showed increase in visual acuity to an average of 0.55±0.35 a year after the surgery; by that time, the maximum refractive power of the cornea decreased to an average of -44.5±3.0 D. The area of stromal thinning was thickened by donor corneal flap. No signs of rejection were detected over the entire observation period. CONCLUSION: Intralamellar bandage keratoplasty may be the method of choice to stop further progression of PMD with improvement of optical properties of the cornea.

[Comparative analysis of modern methods of preparing donor material for endothelial keratoplasty]. / Sravnitel'naia otsenka sovremennykh sposobov podgotovki donorskogo materiala dlia éndotelial'noi keratoplastiki.

PURPOSE: To evaluate various methods of stripping Descemet's membrane of a donor corneoscleral flap for Descemet's membrane endothelial keratoplasty (DMEK). MATERIAL AND METHODS: The study included 60 corneoscleral flaps (mean donor age was 62.9 years) from the eye bank of Research Institute of Eye Diseases, which were not suitable for clinical use due to positive serological results. Four alternative methods of donor material dissection in preparation for DMEK were compared: SCUBA (group A), our newly suggested method utilizing intracapsular ring (group B), 'liquid bubble' (group C), 'big bubble' (group D). Parameters under evaluation were mean transplant preparation time, density of endothelial cells before and after dissection, presence of complications during detachment of Descemet's membrane. RESULTS: Mean detachment time in group A was 8.5 min, in group B - 7 min, in group C - 8 min, and in group D - 5 min. Loss of endothelial cells as compared with baseline was in average 10.5% in group A, 9.3% in group B, 10.7% in group C, and 10.3% in group D. Group A had two cases with complications occurring during separation of Descemet's membrane, group B had one such case, group C - 2 cases, and group D - 3 cases. Histologic examination confirmed absence of stromal fibers on the detached Descemet's membrane in groups A, B and C. CONCLUSION: Among the described methods of preparing donor material for DMEK surgery, all except 'big bubble' proved equal in terms of resulting transplant quality. The 'big bubble' dissection technique requires more time to complete, while the resulting transplant has stromal fibers. Our newly suggested method of Descemet's membrane stripping that utilizes intracapsular ring proved safe and effective alternative for preparing donor material for DMEK.

[Methods of preserving donor corneas]. / Metody konservatsii donorskikh rogovits.

Corneal transplantation is the most successful and frequently performed allotransplantation procedure. Benign outcome of penetrating and posterior keratoplasty depends on viability of the corneal tissue and presence of the proper endothelial layer, which retaining is one of the main objectives of preservation of donor material. Methods designed to reach this goal may be classified according to storage duration as short-term (storage in a moist chamber), medium-term (hypothermia), long-term (organ cultivation) and unlimited (cryopreservation). While there are reports of successful application of cryo-conserved corneas for penetrating keratoplasty, its use for this type of transplantation is limited due to complexity of the method and very high requirements for the quality of donor material. However, being a method of unlimited storage, it still attracts the attention of researchers. Taking into account the ongoing development of innovative keratoplasty technologies and the tendency for predominant use of layered grafts that in some cases do not need viable endothelium, methods of preservation of such material for anterior lamellar and intralamellar keratoplasties become relevant. In this context, cryopreservation without the use of cryoprotective agents is promising because it allows simple and fast accumulation of large amount of material with long storage time. Further research on the development of preservation methods of the corneal endothelial layer at sub-zero temperatures may allow storing the material by cryopreservation that will be suitable for penetrating and posterior keratoplasty.

[New biophotonics methods for improving efficiency and safety of laser modification of the fibrous tunic of the eye]. / Novye metody biofotoniki dlia povysheniia éffektivnosti i bezopasnosti lazernykh tekhnologii modifikatsii fibroznoi obolochki glaza.

The article describes a newly developed and tested diffractive optical element (DOE) that converts non-uniform radiation of the laser output into a homogeneous ring. The Gerchberg-Saxton algorithm is shown to be well suited for achieving annular intensity distribution. Testing this ring transducer on threshold-plasticity cornea demonstrated the reversibility of axisymmetric changes in the cornea. Atomic-Force microscopy of the area of maximum stresses in the corneal periphery showed no significant changes in the structure of the cornea when irradiated in the selected mode. Measurement of Young's modulus of the corneal surface areas after their irradiation also revealed no changes in the elastic properties, while examination of the corneal structure demonstrated the absence of significant structural changes in irradiated samples compared with intact ones.