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

[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.

[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.

[Association of polymorphic markers rs7947461 of the TRIM21 gene and rs33996649 of the PTPN22 gene with the risk of developing exogenous dry eye syndrome]

In this age of technological advancement, an increasing number of people is being exposed to external risk factors of damaging their ocular surface (wearing contact lenses, electromagnetic radiation from computers, mobile devices, etc.). However, the presence of external factors does not lead to a 100% risk of developing the dry eye disease (DED). The trigger mechanism in the development of autoimmune lesions of the ocular environment in some systemic diseases is known to be associated with molecular genetic factors. The search for molecular genetic disorders is based on the analysis of polymorphic markers of a number of genes responsible for the state of the eye surface.

PURPOSE

To study the relationship of polymorphic markers rs7947461 of the TRIM21 gene and rs33996649 of the PTPN22 gene with the risk of developing dry eye syndrome of exogenous etiology.

MATERIAL AND METHODS

The study included 57 people with exogenous risk factors for DED development. The control group included volunteers without a history of ophthalmic pathologies (n=75). Genotyping was done by real-time polymerase chain reaction followed by melting curve analysis. Statistical processing of data was done using the Statistica 6.1 RUS software for statistical analysis.

RESULTS

In the course of the study, 31 patients of the main group were diagnosed with DED and separated into the 1st subgroup; DED diagnosis was not confirmed in 26 patients, who were put into the 2nd subgroup. The 1st subgroup showed a significant increase in the frequency of predisposing genotypes of the TRIM21 and PTPN22 genes. The relative risk of developing DED turned out to be 2.5 and 4.86 times higher, respectively. In the 2nd subgroup, no statistically significant data was found on the presence of predisposing genotypes of polymorphic markers of the TRIM21 and PTPN22 genes (p=0.3).

CONCLUSION

The revealed association of polymorphic markers rs7947461 of the TRIM21 gene and rs33996649 of the PTPN22 gene with the risk of developing DED of exogenous etiology puts these loci as possible markers for diagnosing this pathology.

[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.

[Results of enzyme-linked immunoassay of the blood serum in patients with infectious and inflammatory diseases of the anterior segment of the eye]

PURPOSE

To evaluate the clinical significance of the data obtained during enzyme-linked immunosorbent assay (ELISA) of the blood serum of patients with inflammatory diseases of the anterior eye segment compared to a group of healthy volunteers.

MATERIAL AND METHODS

A retrospective analysis of the results of serum ELISA of 200 patients with chronic keratoconjunctivitis and keratouveitis was performed using the solid-phase IFA method in order to detect the presence of antibodies to herpes simplex viruses of 1 and 2 types (HSV 1, 2), cytomegalovirus (CMV), Chlamydia trachomatis and Toxoplasma gondii. The control group consisted of 34 healthy volunteers with no signs of inflammation of the eye tissue.

RESULTS

There were no significant differences in the frequency of detection of both «acute-phase» IgM and «chronic» IgG to HSV and CMV between patients of the main group and healthy volunteers (ρ≥0.05). The levels of IgG to Toxoplasma gondii in the study group were three times higher than in the control group (ρ≤0.05). A comparative analysis of the frequency of detection of antibodies to Chlamydia trachomatis showed statistically significant differences between the groups and more frequent detection of immunoglobulins classes A, G and M in patients with inflammatory eye diseases (ρ≤0.05).

CONCLUSIONS

The absence of statistical differences with the control group in the frequency of detection of active HSV and CMV infections in patients with inflammatory diseases of the anterior eye segment when using ELISA allows to recommend the use of additional methods of examination such as polymerase chain reaction (PCR) and real-time PCR (RT-PCR) with identification of pathogen genetic material in the available biological secretions. The increase in IgG titers to toxoplasma in patients of the main group apparently indicates a cross-stimulation of antibody synthesis against the background of a chronic inflammatory process. Significant differences in the frequency of detection of all types of antibodies to chlamydiae suggests a significant etiological role of this pathogen in the development and maintenance of chronic inflammation in the anterior eye segment.