[Current view on the pathogenesis of immune-mediated inflammatory diseases associated with ocular manifestations]

This literature review discusses the new concept of pathogenesis of systemic immune-mediated inflammatory diseases (IMIDs), presents their classification and analyzes their association with ocular manifestations.

[Confocal microscopy of the corneal nerve fibers]

This article presents the results of confocal microscopy of the corneal nerve fibers (CNF). The transparency of the cornea provides a unique potential for in vivo visualization of thin unmyelinated nerve fibers at the level close to morphological study. Modern software eliminates the need for manual tracing of the confocal image fragments, allows objectifying the process of assessment of CNF structure based on quantitative indicators characterizing the length, density and tortuosity of the main nerve trunks. Clinical application of structural analysis of the CNF has two potential directions associated with immediate tasks of ophthalmology, as well as with interdisciplinary affairs. In terms of ophthalmology, this primarily concerns various surgical interventions potentially affecting the state of the cornea, and chronic pathological processes in the cornea of different nature. Such studies could analyze the degree of changes in the CNF, or the particularities of corneal reinnervation. The potential for interdisciplinary studies lies in using CNF as biomarkers of systemic polyneuropathies. Relative simplicity, high level of direct visualization of the thin nerve fibers, and the obtained results allow recommending corneal confocal microscopy as a tool for primary screening and consequent monitoring of neuropathies in addition to the conventional methods.

[Morphological evaluation of the results of laser activation of scleral hydropermeability in the treatment of glaucoma]

PURPOSE

The study attempted to experimentally substantiate the possibility of using the laser activation of scleral hydropermeability (LASH) technique in glaucoma treatment by morphological evaluation of treatment outcomes.

MATERIAL AND METHODS

The pulsed-periodic radiation from an Er-glass fiber laser (λ=1.56 μm) was used. The model experiment consisted of evaluating ultrafiltration of fluid through the tissues of human sclera autopsy specimen according to the original technique using neodymium chloride-based labeling agent and scanning electron microscopy. The clinical part of the study consisted of optical coherence tomography (OCT) and laser confocal microscopy of the sclera and conjunctiva (CMSC) performed in vivo immediately after laser treatment in the laser application sites in 5 patients (5 eyes) aged 57 to 68 years with uncompensated advanced (IIIb-c) stage of glaucoma who had previously underwent LASH surgery.

RESULTS

Results of morphological evaluation after LASH revealed structural changes indicating increased transscleral ultrafiltration: increased intrastromal hyporeflective areas in the sclera, thinning of collagen fibers, formation of porous structures. Using an original technique involving neodymium chloride-based labeling agent and scanning electron microscopy, we were able to prove the enhancement of transscleral ultrafiltration. The results of the experiment were confirmed by in vivo OCT images of the sclera and CMSC performed in 5 patients with advanced glaucoma after LASH surgery, in which tissue decompaction in the laser-exposed areas was clearly visualized.

CONCLUSION

The revealed structural changes indicate the possibility of reducing intraocular pressure after LASH by the means of forming scleral porous structures and increasing transscleral ultrafiltration. Experimentally selected optimal mode of laser exposure (0.66 W with total exposure time of 6 seconds) during LASH helps avoid gross destructive changes in the eye tissues, making the proposed intervention a sparing approach to the treatment of glaucoma.

[Correction of refractive disorders after surgical treatment of recurrent pterygium (case study)]

Lamellar keratoplasty is the most effective and safe method of surgical treatment of recurrent pterygium, providing restoration of the corneal frame and optical properties and a high anti-relapse effect due to the barrier properties of the lamellar graft. However, potential postoperative changes in the regularity of the anterior and posterior surfaces of the cornea (especially in case of advanced stage of fibrovascular tissue growth) do not always allow achieving high functional results of treatment. The article presents a clinical case that demonstrates the effectiveness and safety of excimer laser correction of refractive disorders after surgical treatment of pterygium.

[Clinical and morphological characteristics of corneal epithelial dystrophy (clinical observations)]

This paper presents clinical observations that can be regarded as degeneration of the basement membrane of the corneal epithelium. Difficulties in identifying such forms of corneal dystrophies, on the one hand, are associated with limitation and polymorphism of the clinical picture, and, on the other hand, with insufficient information content of the basic diagnostic methods (i.e. the methods used during the initial examination). The presented clinical cases allow singling out the alarming and pathognomonic signs of the disease in the diagnostic algorithm. In the first case, attention should be paid to biomicroscopic changes in the superficial layers of the cornea and the optical defects, which can be regarded as a manifestation of an irregularity of corneal refraction. Identification of pathognomonic signs of the disease is possible on the basis of a detailed, close-to-morphological study of the structure of superficial corneal layers using confocal microscopy and optical coherence tomography. At the same time, the localization of the detected changes at the level of epithelial basement membrane and its basal sections is of crucial significance for substantiating the diagnosis. In addition, according to the literature data, recurrent erosions of the cornea of unclear etiology should be attributed to presumptive signs of degenerative changes in the basement membrane of the epithelium.

[Optical coherence tomography in the diagnosis of pathologies of the horizontal portion of the lacrimal drainage system]

This article reviews literature on the use of optical coherence tomography in studying the anatomical structure of the proximal lacrimal drainage system, as well as in diagnosing its pathological changes. Determining the reference values of the parameters of the lacrimal punctum and the lacrimal canaliculus remains an important issue. The review describes the advantages and disadvantages of this method, as well as the prospects for its application in clinical practice.

[Nerve fiber structure after different types of corneal transplantation]

This review presents basic information about the state of corneal nerve fibers and Langerhans cells before and after keratoplasty. Keratoplasty is a common corneal surgery that carries a risk of graft rejection. The state of corneal nerve fibers can vary after different types of keratoplasty. Corneal confocal microscopy allows in vivo evaluation of the cornea, which can help assess the condition of corneal nerve fibers, as well as reveal the presence of Langerhans cells. Further research in this direction would contribute to identifying the relationship between the state of corneal nerve fibers, the presence of Langerhans cells, and graft rejection.

[Laser-induced damage to the cornea after YAG laser surgery of anterior segment structures]

Laser photodestruction (LPD) of tissues is the basis of modern laser reconstructive surgery in ophthalmology. The most common laser technologies based on LPD mechanisms include YAG laser capsulotomy (discission) (LD) of secondary cataract and YAG laser iridectomy (LIE) for glaucoma. Laser reconstructive interventions for secondary cataract, as well as LIE, have a number of advantages over traditional surgery, but at the same time are associated with the risk of complications, including in the cornea. Corneal endothelium is the most susceptible to laser damage, while Descemet's membrane and corneal stroma are injured less often. This review describes cases of iatrogenic perforation and purulent inflammation of the cornea. In the long-term, laser interventions can lead to bullous keratopathy and corneal graft rejection. At this time, the most popular and available among the methods for assessing the cornea after YAG laser interventions is the method of specular microscopy. Ultrasound biomicroscopy is used less commonly. The modern method of corneal confocal microscopy is practically not used for this purpose, and taking into account the risks of developing laser-induced injuries, it indicates its relevance and the need for further research.

[Role of ultrasound biomicroscopy in assessing the results of laser treatment in capsular contraction syndrome]

The article presents the results of ultrasound biomicroscopy (UBM) measurements of pseudophakic patients with anterior capsular contraction syndrome (CS).

PURPOSE

To analyze the results of UBM in capsular CS before and after laser treatment.

MATERIAL AND METHODS

The study included 42 patients with capsular CS. The HI-scan ultrasound biomicroscope (Optikon, Italy) with 35 MHz UBM probe and the LPULSA SYL-9000 Premio laser (LightMed, Taiwan-USA) were used.

RESULTS

The shrinkage of the capsular bag of the lens was accompanied by a significant decrease in the diameter of the anterior capsulotomy opening, IOL decentration and its displacement towards the posterior pole of the eye, stretching or damage to the ciliary zonule, and an increase in the ciliary body thickness. In 2 cases, ruptures of the ciliary body and its separation from the place of attachment to the iris root were observed. The optimal algorithm of laser treatment was developed to minimize the risk associated with possible aggravation of the clinical manifestations of CS and possible complications during laser treatment.

CONCLUSION

UBM is an effective examination method for CS, which allows assessing the state of the capsular bag of the lens and the ciliary body, evaluating the effectiveness of laser treatment and predicting the risks associated with a high probability of complications.

[State of corneal nerve fibers in systemic amyloidosis]

The term systemic amyloidosis unites a group of diseases with a single pathogenetic mechanism involving diffuse deposition of a pathological fibrillar protein (amyloid) in the intercellular space of various organs. Among the systemic forms of amyloidosis, light chain amyloidosis (AL-amyloidosis) occurs most often in clinical practice, while transthyretin amyloidosis (TTR-amyloidosis) is its most common hereditary form. Laser corneal confocal microscopy (CCM) allows for in vivo and non-invasive assessment of the state of corneal nerve fibers (CNF).

PURPOSE

To assess the state of CNF in systemic amyloidosis by confocal microscopy data obtained in vivo.

MATERIAL AND METHODS

The main study group included 16 patients (6 men and 10 women, mean age 60.5±11.6 years) with morphologically confirmed primary AL-amyloidosis, and 14 patients (5 men and 9 women, mean age 59.4±11.3 years) with genetically and morphologically confirmed hereditary TTR-amyloidosis. The control group included 23 healthy volunteers of the same age range without any neurological pathologies. The state of CNF was assessed by in vivo CCM data recorded on the HRT III system and its consequently processing using authors' self-developed program Liner 1.2. The criteria for neuropathy intensity was the degree of CNF tortuosity characterized by coefficients of anisotropy (K_ΔL) and symmetry (K_sym) of CNF orientation.

RESULTS

According to the NIS scale, the manifestations of neuropathy in the subgroup of patients with TTR-amyloidosis were significantly more pronounced compared to AL-amyloidosis patients. The severity of clinical manifestations of neuropathy did not depend on the duration of TTR-amyloidosis and AL-amyloidosis (Spearman R r_s=0.21, p=0.58 and r_s= -0.49, p=0.055, respectively). Changes in the quantitative indicators (a decrease in the anisotropy coefficient and an increase in the symmetry coefficient of the fibers orientation) confirm increased tortuosity of CNF in systemic amyloidosis.

CONCLUSION

The clinical picture of systemic amyloidosis is characterized by polymorphism of neurological manifestations that include various symptoms of damage to the peripheral somatic and autonomic nervous system. In vivo CCM can be used to reveal qualitative and quantitative changes in CNF in patients with systemic amyloidosis. However, statistical unreliability of the identified quantitative changes allows considering the state of CNF in amyloidosis only as a component of the disease monitoring algorithm, but not as a biomarker of the disease.

[Confocal microscopy in the diagnosis of acanthamoeba keratitis]

Acanthamoeba keratitis (AK) is a dangerous disease of the cornea, its prevalence has increased significantly due to widespread usage of contact lenses. The similarity of the clinical manifestations of AK to other infectious keratitis (especially herpetic keratitis) requires introduction of a rapid diagnosis method into clinical practice.

PURPOSE

To evaluate the capabilities of corneal confocal microscopy (CCM) in the diagnosis of acanthamoeba keratitis.

MATERIAL AND METHODS

We examined 33 patients (35 eyes) with suspected acanthamoeba keratitis using light and laser confocal microscopy of the cornea (ConfoScan and HRT devices, respectively).

RESULTS

CCM was technically feasible in 23 of 35 cases (65.7%). Acanthamoeba cysts were detected in 16 cases (69.6%); trophozoites were visualized in 17.4% of cases; signs of keratoneuritis were detected in 12 eyes (52.2%); in 7 cases (30.4%), hyporeflective honeycomb-like cavities were observed in the stroma; deep stromal striae were observed in 9 cases (39.1%); activated keratocytes were detected in 11 patients (47.8%), and Langerhans cells were detected in 19 cases (82.6%).

CONCLUSIONS

The main diagnostic value of confocal microscopy is the detection of direct markers of AK - cysts and trophozoites of Acanthamoeba. Both light and laser CCM techniques are suitable for the diagnosis of AK, but the resolution of laser confocal microscopy is higher. The non-invasive nature of this method and the possibility of multiple subsequent examinations make it possible to verify the diagnosis of acanthamoeba keratitis and monitor the treatment.

[First results of clinical diagnostic analysis of post-COVID peripheral neuropathy]

This analysis of ocular manifestations of the COVID-19 that can occur both in the acute and the post-COVID period focuses on pathological changes associated with hypercoagulation: thrombosis of the central retinal vein, occlusion of the central retinal artery, and decreased peripapillary perfusion. Potential changes in corneal nerve fibers (CNF) associated with coronavirus infection remain poorly understood. Meanwhile, previous studies have shown the possibility of using CNF as biomarkers of polyneuropathy (PNP).

PURPOSE

To study clinical and diagnostic features of post-COVID PNP.

MATERIAL AND METHODS

We examined 9 female patients aged 32 to 51 years who had suffered an infection caused by SARS-CoV-2 of varying severity. The patients were divided into two groups: the first consisted of 6 patients with clinical manifestations of PNP in the form of neuropathic pain, the second - 3 patients without clinical manifestations. Patients of group 1 underwent comprehensive examination including neurological examination, confocal microscopy of the cornea (in vivo CM), electroneuromyography (ENMG) of the nerves of the upper and lower extremities, quantitative sensory testing in the zone of painful sensations, while patients of group 2 only underwent in vivo CM.

RESULTS

All patients of the first group, within 5-40 days after the onset of infection caused by SARS-CoV-2, exhibited symptoms of damage to various parts of the nervous system (peripheral nerves, thoracic spinal roots, trigeminal nerve). The main - and in most cases the only - symptom of the disease was neuropathic pain syndrome. In Guillain-Barré syndrome, for the first time using in vivo CM, the following changes were revealed: enlargement of in Langerhans cells, shortening of CNF and their processes, presence of neuromas.

CONCLUSION

The standard neurological examination of patients with post-COVID neuropathy should be supplemented with special diagnostic methods for assessment of structural and functional state of the peripheral nerves. The in vivo CM method is capable of non-invasive assessment of changes in thin CNF and, with accumulation of empirical data, can be included in the algorithm for diagnosing post-COVID PNP.

[Experimental investigation of the safety of terahertz radiation in corneal hydration assessment]

Application of terahertz (THz) radiation in novel non-invasive biomedical technologies has recently received considerable attention. However, experimental data about the safety of exposure to THz radiation for biological objects (including eye structures in vivo) are limited. To our knowledge, the safety of THz reflectometry (frequency range of 0.30-0.40 THz) has not been closely examined in an animal model with subsequent morphological assessment of corneal tissues.

PURPOSE

To assess the safety of pulsed THz radiation with various parameters (time, power, and frequency) for the cornea in a rabbit model.

MATERIAL AND METHODS

The sample for the current study consisted of 18 Chinchilla rabbits (18 eyes). Corneal imaging and epithelial cell density before and after the exposure were evaluated using confocal laser scanning microscopy (CLSM). The histological study for objective assessment of the cornea state (day 1 and day 14) was performed after experiment termination.

RESULTS

Single and multiple exposures of laser radiation at a frequency below 0.1 THz and power density below 30 nW/cm² do not cause visible structural changes in any layers of the rabbit cornea. The results obtained in the long-term period showed insignificant reversible morphological changes only within the epithelium.

CONCLUSION

The described parameters of terahertz and subterahertz radiation can be considered safe for assessing changes in corneal epithelium hydration level using non-invasive methods based on THz reflectometry.

[Methods and clinical significance of the condition of corneal nerve fibers]

The review provides basic information about embryology, structural features, biochemical composition, functions and classification of corneal nerve fibers, and describes anatomical, histological and functional diagnostic techniques for corneal nerves. Each method for analyzing the structure of the nerve fiber, its advantages and disadvantages are described in detail, including the history of the development of confocal microscopy (laser and light) and esthesiometry (contact and non-contact). The article also presents the criteria according to which the structure of the nerve fiber is estimated using laser confocal microscopy, and the shortcomings of these criteria. Additionally, the article reports on the futility of the use of modern esthesiometry methods.

State of corneal nerve fibers after laser-assisted in situ keratomileusis

PURPOSE

To assess the state of corneal nerve fibers (CNF) based on quantitative parameters after laser correction of myopia using LASIK.

MATERIAL AND METHODS

The study examined 141 eyes - 80 eyes with myopia and 61 emmetropic eyes. In 47 cases a microkeratome was used to form a corneal flap, and in 33 cases a femtosecond laser was used (LASIK and FemtoLASIK, respectively). Confocal microscopy was performed before, as well as 1, 3, and 6 months after correction. Objective analysis of CNF involved automatic calculation of the anisotropy (K_ΔL) and symmetry (K_sym) coefficients of CNF orientation in the Liner 1.2S software.

RESULTS

Lower values of K_ΔL were revealed in myopia as compared to emmetropia. Regardless of the method of flap formation, no CNF could be detected in the central cornea 1 month after myopia correction. In all cases after FemtoLASIK and in 2 cases after LASIK, CNF in the central cornea were first visualized after 3 months, and after 6 months CNF could be detected in all cases. At a similar observation time, CNF were visualized both after LASIK and after FemtoLASIK in the superior and inferior peripheral portions of the cornea. Analysis of long-term postoperative changes in K_ΔL and K_sym revealed a decrease in the former and an increase in the latter.

CONCLUSION

Evaluation of the state of CNF after corneal refractive correction should take into account the initial changes in CNF in myopia that are possibly associated with an increase in axial eye length. A more dynamic restoration of innervation was noted in cases where the flap was formed with the femtosecond laser, which may be explained by the fact that the mechanism of tissue separation when using this type of coherent radiation is gentler. Considering the changes in the quantitative indicators characterizing the state of CNF, the question of «completeness» of the restored CNF as a result of reinnervation remains open.

[Indications for retinal laser coagulation in the treatment of retinoschisis and rhegmatogenous retinal detachment]

PURPOSE

To determine the indications and assess the effectiveness of laser coagulation of the retina (RLC) after different types of surgeries for retinal detachment (RD), except vitrectomy.

MATERIAL AND METHODS

The study included 160 patients (165 eyes) with various types of retinal detachment and retinoschisis who remained under observation for 11 years.

RESULTS

In case of retinal tear with a slight local RD (less than one quadrant), we recommend the use of RLC as monotherapy. Such patients are indicated to undergo regular examinations (1 month, 3 months, 6 months, 1 year). Due to risk of tractional defects of the retina in the lower quadrants during the introduction of gas-air mixture into the vitreous cavity, in the presence of retinal pathology it is recommended to perform RLC before the pneumatic retinopexy stage. In large retinal tears, despite their upper localization, pneumatic retinopexy is not indicated due to the possibility of gas spilling over the edges of the tear under the retina, leading to an increase in the initial size of the tear and spread of RD. We noted the effectiveness of RLC monotherapy for retinal detachment of various localization. After sealing the sclera, retinal laser coagulation on the shaft along the seal is necessary to limit the tear along the edge, since over time the seal may shift causing a relapse of RD.

CONCLUSION

The study has confirmed the effectiveness of laser coagulation of the retina as an independent method for the treatment of retinoschisis and retinal tears with local detachment.

[The effects of corneal collagen cross-linking on the corneal structure in keratoconus]

The article reviews the key information regarding morphological changes in keratoconic corneas and dramatic alterations of the corneal tissue induced by corneal cross-linking according to data obtained with in vivo corneal confocal microscopy, presents basic information on keratoconus visualization techniques widely used for diagnosis, monitoring of ectasia, as well as efficacy assessment of its treatment, and lists basic principles of corneal cross-linking procedure and confocal microscopy with consideration of morphology specifics of keratoconic corneas. The article also discusses prospective benefits of further research and longitudinal studies aimed to define the origin of keratoconus and to develop advanced corneal cross-linking protocols.

[Changes in corneal nerves fibers in the early stages of Parkinson's disease according to in vivo confocal microscopy (preliminary report)]

One of the research directions of the so-called non-motor manifestations of Parkinson's disease (PD) is associated with the assessment of structural and functional changes in the organ of vision. An assessment of the state of thin non-myelinated corneal nerve fibers (CNF) in Parkinson's disease seems to be promising considering the neurodegenerative nature of the disease, as well as the possibility of objective intravital assessment of both functional and structural changes in CNF.

PURPOSE

To analyze the changes in the course and structure of corneal nerve fibers in the early stages of Parkinson's disease based on an objective algorithm of in vivo corneal confocal microscopy (CCM).

MATERIAL AND METHODS

The study was conducted on a group of 16 patients aged 39 to 66 years with verified diagnosis of PD. In addition to standard neurological and ophthalmological examinations, all patients underwent IVCCM on a Heidelberg Retinal Tomograph device with special Rostock Cornea Module (HRT3 RCM), followed by processing of the obtained images using a uniquely designed analysis algorithm.

RESULTS

A significant decrease in the directional anisotropy coefficient and an increase in the directional symmetry coefficient of the nerve fibers of the cornea were established (average values 3.15±1.08 and 0.92±0.04, respectively); in healthy individuals of the identical age range these indicators are 3.5±0.85 and 0.86±0.11, respectively. In addition, qualitative structural changes were noted, which consisted of an increase in the number of branches from the main nerve trunks, an increase in the tortuosity of CNF, multidirectionality, and "beaded" shape. In 9 cases, the presence of macrophages was revealed - dendritic Langerhans cells, which is an indirect sign of the inflammatory process.

CONCLUSION

The preliminary nature of the results obtained in this study and the need for further research in this area are related, on the one hand, to a small sample of observations and, on the other hand, to the criterion used to assess the status of CNF based on a comparative analysis with conditionally normal indicators. In the future, in order to solve the problem of the uniqueness of changes in CNF and the possibility of using these changes as a marker for PD progression, longitudinal studies are required to reveal the presence or absence of a correlation between the stage of the disease, the results of known monitoring methods (e.g. electromyography) and quantitative indicators of the status of CNF.

[Atomic force microscopy in the study of retinal structure]

The review addresses the current state of atomic force microscopy (AFM) usage in ophthalmology. Briefly presented here are the history of the development of AFM, principles and modes of operation, its advantages, disadvantages, as well as a comparison with other types of microscopy. The review describes the capabilities of AFM in visualization of various structures of the eye. A significant part of the review is devoted to the study of the retina, which arouses great interest among researchers. In particular, the possibilities of AFM for visualization at the submicron level of various structures in the retina, such as the internal limiting membrane, membrane cells, Müller cells, retinal pigment epithelium in their normal state and in the presence of a pathology (age-related macular degeneration, diabetes mellitus) were reviewed. In addition, several study papers were analyzed, providing a base for the judgement of the mechanical properties of said structures. An AFM study of the visual pigment rhodopsin helped identify its dimeric structure. The stability of the rhodopsin molecule was proved to be determined by the degree of strength of its individual segments connected to each other. The AFM method is a highly accurate method that helps solve many fundamental and practical problems, particularly in ophthalmology.

[Antiangiogenic therapy in high-risk keratoplasty]

PURPOSE

To analyze the effectiveness and safety of VEGF inhibitor used to improve keratoconus transplant survival in patients with corneal neovascularization as stand-alone and in combination with laser coagulation of ingrowing vessels before keratoplasty.

MATERIAL AND METHODS

The study included 56 patients (56 eyes) with corneal opacifications of various etiology complicated by corneal neovascularization (CNV). The patients were divided into three groups. The 1st group included 27 patients with diffuse CNV who were undergoing an antiangiogenic therapy using anti-VEGF drug, the 2nd group - 14 patients with stem cell CNV who underwent laser coagulation of major corneal vessels combined with subconjunctival administration of drug before keratoplasty; the control group consisted of 15 patients with mixed type CNV who were undergoing conventional treatment without antiangiogenic therapy.

RESULTS

During the follow-up (24.5±4.84 months, 4 to 25 months), transplant rejection reaction was recorded in 7 (23%) patients of the 1^st group, 5 (35%) patients of the 2^nd group and 9 (60%) patients of the control group.

CONCLUSION

Subconjunctival administration of Aflibercept as a stand-alone measure and in combination with laser coagulation of ingrowing vessels may increase the chances of transparent transplant acceptance in high-risk keratoplasty.

[Changes in corneal nerve fibers after microinvasive cataract surgery (a preliminary report)]

INTRODUCTION

Potential changes in corneal nerve fibers (CNF) induced by cataract phacoemulsification remain insufficiently studied. The need for research in this direction is dictated by a number of circumstances: introduction of corneal confocal microscopy into clinical practice, the need for phaco surgery in the presence of corneal changes of various genesis, the possible negative impact of laser radiation during hybrid (femtosecond laser-assisted) phacoemulsification.

PURPOSE

To assess the changes in CNF after various methods of microinvasive cataract surgery.

MATERIAL AND METHODS

The studies were conducted in patients aged 50 to 60 years who underwent standard ultrasound and hybrid phacoemulsification; the patients were respectively divided into two groups (30 surgeries each). The algorithm for assessing the state of CNF involved laser confocal microscopy using original software. To quantify the state of the nerves, two coefficients were used: CNF orientation anisotropy (KΔL) and CNF orientation symmetry (K_sym).

RESULTS

Regardless of the surgery technique, tendencies were noted for the orientation anisotropy coefficient to decrease and the orientation symmetry coefficient to increase, which are conditionally comparable with previously identified age-related changes in CNF. After hybrid phacoemulsification, a decrease in the orientation anisotropy coefficient 2-2.5 months after the intervention turned out to be statistically less significant compared to the standard ultrasound technique.

CONCLUSION

Further research should be aimed at analyzing the long-term results of both microinvasive phacosurgery techniques and the «classical» extracapsular cataract extraction, which remains the method of choice in a number of clinical situations.

[The effect of the tear film on the results of a direct assessment of the sensitivity of the cornea]

Attempts to find clinical application for esthesiometry are associated with studying sensitivity disorders that occur in various diseases (diabetes mellitus, keratitis of various etiologies, corneal erosion, dry eye syndrome), as well as after surgical interventions.

PURPOSE

To evaluate the influence of the tear film on the results of direct assessment of corneal sensitivity.

MATERIAL AND METHODS

The study was conducted in a group of 20 healthy volunteers. Criteria for inclusion in the group: absence of any ocular and general systemic diseases in the anamnesis, normal indicators of tear production and stability of the tear film according to Schirmer and Norn tests. The process of testing involved a specially designed device that was used to exert a dosed force by jets of air on the frontal corneal surface and the pressure was recorded at the moment of tactile sensations and at the breakup time of tear film, as an indicator of its biomechanical stability.

RESULTS

A strong correlation have been found between the pressure of the air stream at the moment of getting tactile sensations and at the breakup of the tear film (R=0.91, p=0.0094). The obtained data indicate that the biomechanical resistance of the lacrimal film is a significant factor preventing the correct assessment of the results of direct corneal esthesiometry in the range of values close to conditionally normal sensitivity.

CONCLUSION

In this regard, in their current technical implementation, modern esthesiometers can only be used for monitoring (not for diagnosis!) of pathological processes by analyzing relative (compared to each other) - rather than absolute - sensitivity measures (optimally in combination with analysis of the structural changes in the corneal nerves based on laser confocal microscopy).

[Phacosurgery effects on the condition of corneal nerve fibers]

The question of potential changes in the nerve fibers of the cornea induced by phacosurgery remains poorly investigated. This is a review of results of many individual studies aimed at assessing the condition of corneal nerve fibers following different techniques of cataract removal. The authors substantiate the necessity for structural analysis of fiber changes based on in vivo confocal microscopy of the cornea. Functional assessment of corneal sensitivity (esthesiometry) does not allow objective conclusions, for several reasons. Further studies on corneal nerve changes after phacosurgery could be directed at improving software products for objective quantitative assessment of corneal nerve fibers and analyzing long-term results of various phacosurgery techniques.

[Early diagnosis of diabetic polyneuropathy based on the results of corneal nerve fibers examination]

Laser corneal confocal microscopy (CCM) is a method of objective visualization of thin corneal nerve fibers (CNF), the structure of which changes in patients with diabetes mellitus (DM).

PURPOSE

To conduct comparative analysis of the results of CNF assessment using CCM and other known neurological instrumental techniques as well as evaluate their applicability to the early diagnosis of diabetic polyneuropathy (DPN).

MATERIAL AND METHODS

We examined a total of 46 patients (85 eyes) with type 1 DM and either subclinical (24 patients), or clinical-stage DPN (22 patients) and 50 patients (87 eyes) with type 2 DM (subclinical DPN in 27 patients and clinical-stage DPN in 23 patients). The control group consisted of 34 healthy volunteers (68 eyes). All patients underwent standard ophthalmological examination, CCM with nerve tortuosity assessment (including calculation of coefficients of CNF orientation anisotropy, K_ΔL, and symmetry, K_sym) and interocular asymmetry, electroneuromyography (ENMG), and quantitative sensory testing (QST).

RESULTS

Analysis of the CCM results revealed a reliable decrease in the average K_ΔL values in patients with type 1 and type 2 DM compared with the control group. In the group of patients with type 1 DM and subclinical DPN, correlations were revealed between the CNF tortuosity coefficients and a number of ENMG parameters, such as the M-response amplitude of the peroneal nerve (r=0.73, p≤0.02), M-response amplitude of the tibial nerve (r=0.58, p≤0.01), residual latency (r= -0.62, p≤0.05), and peroneal nerve conduction velocity (r=0.57, p≤0.01). K_sym values correlated with the warm sensitivity threshold (r=0.6, p≤0.008). Among patients with type 2 DM and subclinical DPN, the K_ΔL coefficient correlated with the peroneal nerve conduction velocity (r=0.46, p≤0.02), M-response amplitude of the tibial nerve (r=0.6, p≤0.04), and residual latency of the peroneal nerve (r=-0.56, p≤0.05).

CONCLUSION

The state of thin corneal nerves correlates with functional changes in the peripheral nerves. Pathological changes in CNF in patients with DM can be detected at an early (subclinical) stage of DPN using laser CCM and a program for corneal nerve tortuosity analysis.

[Clinical and morphological changes in the eye in Fabry's disease (a clinical case study)]

The article presents a clinical case of Fabry's disease accompanied by changes in the eye and gives detailed description of standard ophthalmological examination and results of some modern methods of assessing macro- and micro-structure of certain ocular tissues. Fabry's disease (also known as Anderson-Fabry disease, diffuse angiokeratoma of the body, hereditary dystonic lipidosis) is a progressive hereditary multi-systemic disease; more specifically, it is a progressive congenital defect in the metabolism of tissues of the human body. It is included in the list of orphan diseases. One of its local manifestations is development of dystrophic changes in the structure of the cornea with tendency to progress. Early diagnosis of Fabry's disease is crucial, but its extensive and 'mixed' symptoms often mask the true causes of pathological changes, which leads to late diagnosis.

[Results of laser confocal microscopy of the cornea in viral uveitis (a preliminary report)]

Herpesviruses involve neurotropic activity (they affect nerve cells) and have the ability to induce an immune response (a special tropism for immune tissue), which provides a valid reason for studying the possibilities of visualizing nerve fibers of the cornea and Langerhans cells (LC) in viral uveitis (with prospective applications in early diagnosis).

PURPOSE

To evaluate the results of laser corneal confocal microscopy (CCM) in viral uveitis of varying localization.

MATERIAL AND METHODS

The main study group included 23 patients (23 eyes) diagnosed with unilateral herpesviral uveitis (chorioretinitis), the patients' age varied from 18 to 79 years. The control group comprised 19 healthy volunteers (38 eyes) aged 20 to 75 years. In addition, the paired eyes of the main group patients were examined. In all patients, standard ophthalmologic examination was complemented with CCM performed on the HRT III device with a corneal module, followed by analysis of the course and structure of corneal nerve fibers (CNF) using copyrighted software Liner 1.2.

CONCLUSION

The preliminary results achieved in this study outline the prospects for further research on the state of cornea (in particular, changes in the course and structure of CNF, and the presence of dendritiform cells of Langerhans) with laser CCM in patients with uveitis of various etiologies. These morphological changes also has potential use as diagnostic markers of inflammation of the uveal tract. The main criteria for assessing the state of cornea in viral uveitis include the following: increased tortuosity of CNF, increase in the number and size of Langerhans cells. Further research - in particular, studying the integrated use of diagnostic methods necessary for the verification of viral uveitis, as well as detailed analysis of the history and clinical picture of the disease - is required to substantiate the inclusion of laser confocal microscopy method in the algorithm for the diagnosis of viral uveitis.

[Condition of corneal nerve fibers after laser keratorefractive surgery]

The article reviews studies dedicated to evaluation of corneal nerve fibers (CNF) after various laser keratorefractive methods of correcting refractive error based on confocal microscopy. The matter of studying the dynamics of the condition of CNF after laser keratorefractive techniques continues to be relevant and requires further research with regard to the prevalence of refractive errors on the one hand, and the future life of patients who undergo these procedures, on the other. Certain heterogeneity of the research results presented in this review can be partially explained by the subjective nature of the study algorithm (in particular, the need for manual tracing of nerve fibers) and the lack of objective quantitative indicators of CNF condition suitable for statistical processing.

[Morphological changes in the cornea of patients with recurrent corneal erosion after diamond burr polishing of Bowman's membrane]

PURPOSE

To evaluate morphological changes in the cornea of patients with recurrent corneal erosion (RCE) using laser confocal microscopy before and after abrasive polishing of Bowman's membrane with a diamond burr (APBMDB).

MATERIAL AND METHODS

The study included 17 patients (20 eyes) with established RCE diagnosis; they underwent laser confocal microscopy on HRT III device with Rostock Cornea module (Heidelberg Engineering GmbH, Germany). Morphological analysis of epithelial cells, nerve fibers, stroma and corneal endothelium was conducted. After that, all patients underwent APBMDB. Patient examination was repeated after 1, 3, 6, and 12 months.

RESULTS

Superficial epithelium was intact before treatment in almost all cases. Islets of hyper-reflective cells, drop-shaped arrangements and stripes characterizing abnormal basal membrane were found in basal epithelium layer. Activated keratocytes and anomalous extracellular matrix were observed in the anterior stroma. No changes could be found in the posterior stroma or endothelium. Subbasal nerve plexus had changes in the form of short and atypically formed corneal nerve fiber funiculi, reduced amount of long corneal nerve fiber funiculi, as well as their tendency for forming closed round shapes. Increase in the amount of Langerhans cells was observed. One month after the procedure, pathological changes in the epithelium and basal membrane were absent, reduction in the amount of Langerhans cells and activated keratocytes was observed. Three months after the polishing, continued reduction of the amount of Langerhans cells was noted. Regeneration of nerves partially restored after 6 months; after 12 months, confocal microscopy results were comparable to healthy volunteers.

CONCLUSION

Confocal laser microscopy of the cornea of patients with RCE showed presence of changes in basal epitheliocytes, basal membrane, anterior stroma and corneal nerve fibers, as well as positive dynamics of these changes after abrasive polishing of Bowman's membrane with a diamond burr.

[Complex morphological assessment of anterior capsule of the lens in patients with capsular contraction syndrome (a clinical case study)]

The anterior capsular contraction syndrome (ACCS) in pseudophakic patients is known to be accompanied by postoperative opacity of anterior lens capsule (ALC) and partial or full closure of anterior capsulotomy opening.

PURPOSE

To perform complex morphological assessment of ALC in patients with ACCS.

MATERIAL AND METHODS

The study involved complex analysis of ALC that was removed due to ACCS in the pseudophakic eye in the setting of diabetes mellitus and past vitreoretinal surgery. The following examination methods were used: light-optical microscopy of ALC samples in the form of polychrome-colored semifine sections using optical microscope Leica DM-2500 (Germany), scanning microscopy of ALC surface with EVO LS10 (Carl Zeiss, Germany) microscope, analysis of chemical element composition and its variation of the ALC sample with energy-dispersive spectrometer Oxford X-Max50 (Oxford, UK).

RESULTS

Light-optical microscopy showed altered state and plication of ALC induced by proliferation from inner surface of the fibrocellular tissue, which gradually thickens (up to 360 µm) towards center and causes reduction of anterior capsulotomy opening. Scanning electron microscopy revealed presence of tissue with uneven micro-relief and a porous three-dimensional structure uncharacteristic for capsule on the surface of ALC. Thickness of the fibrous deposition significantly exceeded the thickness of ALC. Evaluation of elemental composition of the fibrocellular tissue showed elevated concentration of sulfur and phosphorus, which indicates high activity of the regenerative process. In the observed case, the regenerative process was of substitute nature because an attempt to restore the lens was accompanied by formation of connective tissue structurally different from original.

CONCLUSION

Complex assessment of an isolated ALC sample allowed revelation of the chain of pathological processes accompanying the development of ACCS.

[Anatomical and functional features of corneal nerve fibers and methods of their evaluation]

Condition of the ocular surface greatly depends on functional integrity of corneal nerve fibers. Improving the methods used to study corneal nerve fibers allows their condition to be timely evaluated and adequately interpreted. The article reviews the structure, function, chemical composition of corneal nerve fibers, specifics of their innervation, as well as application of modern methods of their evaluation in diagnostics of various pathological conditions.

[Clinical features and diagnosis of diabetic polyneuropathy]

Diabetic polyneuropathy (DPN) is a serious complication of diabetes that leads to early disability in patients if late diagnosed. There has been a lot of research into pathophysiological mechanisms of nerve fiber damage and risk factors for neurological complications of diabetes. Early diagnosis of the latter is quite a challenge and, thus, the problem of finding more reliable diagnostic modalities is rather pressing. In this review, an interdisciplinary approach to the said problem, high-end diagnostic methods, and clinical features of DPN are described.

[New approach to corneal nerve fibers morphometry in diabetes mellitus on the basis of confocal biomicroscopy]

AIM

to develop a new approach to morphometric analysis of corneal nerve fibers (CNF) and to evaluate their age-related changes in type 1 and type 2 diabetes mellitus patients.

MATERIAL AND METHODS

The study enrolled 150 participants (300 eyes) aged from 13 to 83 years, of them 37 type 1 diabetes patients (74 eyes), 51 type 2 diabetes patients (102 eyes), and 62 healthy volunteers (124 eyes). All participants were examined with HRT III Rostock Corneal Module (Heidelberg Engineering GmbH). Digital images thus obtained were analyzed with specially developed original software that automatically computes coefficients of CNF orientation symmetry and anisotropy.

RESULTS

A strong inverse correlation has been found between the coefficient of CNF orientation anisotropy and glycated hemoglobin levels (r = -0.83, p < 0.001 and r = -0.79, p < 0.005 in patients with type 1 and type 2 diabetes respectively) as well as the duration of the disease (r = -0,7, p < 0.005 and r = -0.72, p < 0.001, type 1 and type 2 diabetes respectively). On the contrary, the coefficient of CNF orientation symmetry has been shown to be directly correlated with both glycated hemoglobin levels (r = 0.64, p < 0.005 and r = 0.78, p < 0.05, type 1 and type 2 diabetes respectively) and the duration of the disease (r = 0.62, p < 0.05 and r = 0.73, p < 0.05, type 1 and type 2 diabetes respectively). Interocular asymmetry in both coefficients was found in diabetic patients but not in the controls. On the basis of the proposed coefficients, age-related changes in corneal nerve fibers orientation have been determined. Normally, the degree of CNF tortuosity increases with age. The rate of this increase is the highest before the age of 35-40. As shown, type 1 diabetes is associated with low coefficients of CNF orientation anisotropy and high coefficients of CNF orientation symmetry as compared to type 2 diabetes in the same age group.

CONCLUSION

As suggested by the results, the two proposed coefficients that describe the state of corneal nerve fibers can possibly be used for diagnosis and monitoring of diabetic peripheral neuropathy (DPN). However, to produce enough evidence, further studies should be conducted.

[Opportunities for confocal and laser biomicroscopy of corneal nerves in diabetic polyneuropathy]

The review concerns corneal nerves involvement in diabetes mellitus (DM), a pressing issue for ophthalmology and endocrinology. The history of research in this field along with anatomical, physiological, and biochemical features of corneal nerves is provided. Corneal nerves anatomy is described in accordance with Soviet scientific school and contemporary foreign sources. The most part of the paper is devoted to technical description of a confocal microscope and Heidelberg Retina Tomograph with corneal module as well as the feasibility of corneal nerves visualization. Diabetic neuropathy, a threatening complication of DM that can result in lower limb amputations, is discussed. A number of authors suggest confocal biomicroscopy for early diagnosis of polyneuropathy, yet few relevant publications can be found. If effective, confocal biomicroscopy can be considered as a possible screening tool able to detect early signs of diabetes complications and thus to ensure the treatment initiated in a timely manner. The latter is crucial to prevent DM progression to its terminal stage--diabetic polyneuropathy, which is dangerous of lower limb amputations.

[Potentialities of immunofluorescence in examination of retinal vascular system and epiretinal proliferation (experimental study)]

An immunofluorescent method of examination of retinal vascular system and epiretinal proliferative tissue removed during a transciliary surgery has been developed. The proposed method possesses certain advantages, i.e. high-quality visualization of the vascular system in total mounts, particularly, of the capillary loops and fine vascular terminals, the possibility to use specific immunohistochemical markers to identify all kinds of present cells (glia, endothelium, neurons) and evaluate their proliferative activity.

[Visual fixation features after treatment of exudative age macular degeneration]

Changes of visual fixation in patients with choroidal neovascularitation (CNV) associated with age macular degeneration (AMD) after bevacizumab are studied. 45 patients (45 eyes) with active CNV treated with intravitreal bevacizumab were enrolled into the study. Visual fixation was studied before and 3-6 months after treatment using original method that included fundus foto and fluorescein angiography. Fixation relative to fovea and lesion was evaluated. Foveal fixation beyond lesion was found in 9%, foveal fixation within lesion--in 47%, extrafoveal fixation beyond lesion--in 18%, extrafoveal fixation within lesion--in 26% of patients. Changes of fixation localization after treatment was found in 24% patients. Examination of visual fixation may be useful for prognosis of anti-VEGF treatment efficacy in patients with CNV.