[Current state of ophthalmic tonometry]

[Role of point-by-point light sensitivity in the assessment of glaucoma progression]

PURPOSE

This study analyzes changes in light sensitivity in each test point of the visual field in patients with different stages of glaucoma.

MATERIAL AND METHODS

The data of a prospective analytical case-control study were analyzed. All patients underwent assessment of retinal light sensitivity and its variability in 54 points corresponding to the 24-2 program. Mean light sensitivity values were calculated in each point. Intergroup analysis was performed to evaluate changes in light sensitivity in each point.

RESULTS

The range of light sensitivity decrease in the early glaucoma group compared to the control group was from 1.5 to 3.6 dB. The range of light sensitivity decrease in the moderate glaucoma group compared to the control group was from 2.1 to 11.5 dB, and compared to the early glaucoma group - from -0.9 to 7.9 dB. The most frequent decrease in light sensitivity was detected in the nasal sector and along the horizontal line in the upper half of the visual field. This trend persisted within the central 10 degrees of the visual field. The range of light sensitivity decrease in the advanced glaucoma group compared to the control group was from 14.1 to 28.0 dB, and compared to the early glaucoma group - from 11.35 to 26.08 dB, compared to the moderate glaucoma group - from 9.1 to 23.5 dB. The most frequent and severe decrease in light sensitivity was detected in the paracentral zone in the lower half of the visual field.

CONCLUSION

The study analyzed the trends in the development of glaucoma from the early to the advanced stage. The most frequent and severe defect in light sensitivity in cases of verified advanced glaucoma was found in the lower half of the visual field. Points No. 32, 33 and 40 can be indicated as the area of interest in assessing the progression of glaucoma, as they were found to have the most profound changes in light sensitivity as glaucoma progressed.

[Modern achievements in the diagnosis and treatment of glaucoma]

Glaucoma is one of the most difficult and significant ocular conditions. The chronic asymptomatic course of glaucoma progression leads to irreversible deterioration of visual functions. Many aspects of its pathogenesis, the features of its clinical presentation, diagnosis and treatment have been identified in recent years. The results of diagnostic methods: tonometry, perimetry, optical coherence tomography - with glaucoma do not have high specificity due to the large diversity of the population. When determining the target intraocular pressure (IOP), we look at the indicators of the choroidal blood flow and biomechanical stress of the cornea and sclera (fibrous membrane of the eye). Studying visual functions is important in the diagnosis and monitoring of glaucoma. The creation of a modern portable device based on a virtual reality helmet allows examination of patients with low central vision. Structural changes in glaucoma affect the optic disc and the inner retinal layers. The proposed classification of atypical discs allows determining the earliest characteristic changes in the neuroretinal rim for glaucoma in cases of difficult diagnosis. The complexity of the diagnosis of glaucoma is also associated with concomitant pathologies in elderly patients. In cases with comorbidity of primary glaucoma and Alzheimer's disease the structural and functional changes revealed by modern research methods for glaucoma are explained by both the process of secondary transsynaptic degeneration and the death of neurons as a result of an increased IOP. The starting treatment is and its type are fundamentally important for preserving visual functions. Drug therapy with prostaglandin analogues contributes to a significant and persistent decrease in the level of IOP, and mainly by utilizing the uveoscleral outflow pathway. Surgical treatment of glaucoma is an effective way to achieve the target IOP values. However, postoperative hypotension affects the bloodstream both in the central and peripapillary retina. Optical coherence tomography angiography helped establishe that the strongest factor that determines postoperative changes is the difference in IOP, not its absolute level.

Perimetry Criteria For Assessing The Effectiveness Of Retinoprotective Therapy

Objective — To evaluate the effect of the frequency of retinoprotective therapy courses on perimetry parameters, to compare Octopus 900 perimeter with Octopus 600 perimeter, and to assess threshold perimetry results of G-dynamic versus 24-2 programs. Material and Methods — The study involved 17 patients (34 eyes) diagnosed with primary open-angle glaucoma of advanced stage. Group 1 included subjects receiving a course of Retinalamin every 3 months. Group 2 comprised patients undergoing Retinalamin therapeutics every 6 months. Results — At the onset of the study via G-dynamic and 24-2 programs, we did not observe any statistically significant differences between the groups in mean deviation of retinal photosensitivity (MD) and pattern standard deviation of mean retinal photosensitivity (PSD). However, the absolute values differed between groups and between programs. On average, the differences in MD and PSD values obtained in the photosensitivity study with G-dynamic vs. 24-2 programs were -0.36 dB (CI 95%: -4.27; 3.54) and 0.63 dB (CI 95%: 2.37; -1.11), respectively. Hence, studies performed via 24-2 and G-dynamic programs yielded comparable results (no statistically significant differences). However, they could not be identical due to different spatial arrangement of points in different programs. Conclusion — As a result of conducted treatment, retinal photosensitivity did not exhibit statistically significant changes; however, we observed positive dynamics in both groups in MD and PSD parameters of mean retinal photosensitivity. Different devices (Octopus 600 and Octopus 900 perimeters) and different programs (24-2, G-dynamic) yielded different outcomes due to their technical features and capabilities of reproducibility; however, these differences were not statistically significant.

[Modern capabilities of ophthalmic tonometry in pathologically altered corneas]

Changes in intraocular pressure have great influence on the course of various processes in ocular tissues. Presently, the scientific discussion has returned to the theoretical issues of tonometry and the creation of models that would allow assessing the influence of various ocular parameters on IOP values. Some of the modern tonometers (Icare, Tono-Pen) are convenient and effective when measuring IOP in eyes with damaged, uneven or edematous cornea. It is necessary to analyze the results of ophthalmic tonometry by modern methods in accordance with the data of direct intracameral manometry in pathological conditions of the cornea and after keratoplasty.

[Coefficient of biomechanical stress in assessment of the degree of intraocular pressure compensation]

Intraocular pressure is the one modifiable factor, which correct assessment and normalization initiates the treatment of glaucoma. The accuracy of its measurement by traditional methods depends on biomechanical properties of the fibrous tunic of the eye, which in modern clinical practice are most successfully studied by the method of bidirectional applanation of the cornea using the Ocular Response Analyzer (ORA). Mathematical integration of the parameters it measures makes it possible to calculate the coefficient of biomechanical stress (K_bs) that characterizes changes in the fibrous tunic of the eye induced by intraocular pressure, and serves as a criterion for intraocular pressure compensation.

PURPOSE

To determine the range of normal values of the K_bs coefficient, and to evaluate its specificity and sensitivity as a criterion for the degree of intraocular pressure compensation.

MATERIAL AND METHODS

Two consecutive studies on representative clinical material were used to determine the range of normal K_bs values in patients without significant ophthalmic pathologies (400 patients, 800 eyes) and establish the sensitivity and specificity of the coefficient in the diagnosis of glaucoma in patients with newly diagnosed glaucoma (673 patients, 1346 eyes). The age and gender composition of patients in both study groups was similar.

RESULTS

The cut-off value for K_bs is 1.0. In the range of values from 1.0 to 1.09, additional risk factors for glaucoma progression must be taken into account to assess intraocular pressure compensation. In cases when K_bs is equal to or exceeds 1.1, the intraocular pressure is considered elevated and a high risk of disease development or progression is predicted. In glaucoma patients with uncompensated intraocular pressure, the specificity of K_bs is 81.5%, the relative specificity (including the borderline range) is 98%. With K_bs values over 1.1, its specificity reaches 100%.

CONCLUSION

The performed clinical and statistical analysis demonstrates high sensitivity and specificity of the biomechanical stress coefficient in the diagnosis and treatment of glaucoma.

[Effect of retinal protective therapy on optical coherence tomography angiography (pilot study)]

PURPOSE

To assess the influence of the frequency of retinal protective therapy courses on the indicators of regional hemodynamics of the eye.

MATERIAL AND METHODS

The study included 17 patients (34 eyes) with a diagnosis of primary open-angle glaucoma (POAG), advanced stage. The patients were divided into 2 groups: the first group received a course of retinal protective therapy with Retinalamin every 3 months, the second group received a course of retinal protective therapy with Retinalamin every 6 months. All patients underwent standard ophthalmological examination including standard automatic perimetry according to the 24-2 program, optical coherence tomography angiography (OCT-A) of the macular area and optic disc.

RESULTS

The comparison of hemodynamic parameters of all vascular plexuses of the retina at the beginning and at the end of the study, as well as intergroup comparison did not reveal any statistically significant differences (p>0.05). However, when studying the density and fractal dimension of the vascular bed, multidirectional trends were observed. Specifically, in the peripapillary region, there was a decrease in the length from 19.8 (1/mm) to 19.0 (1/mm) (p=0.37) and the density from 36.6% to 35.7% (p=0.63) of the vascular bed of the peripapillary capillary plexus of the retina in patients of the first group. In the superficial vascular plexus, the trend in the density of the vascular bed in both groups slightly changed (in group 1 - 38.1% and 38.3%, p=0.97; group 2 - 37.8% and 38.7%, p=0.46). The fractal dimension of the vascular bed in the first group tended to increase during treatment from 18.8 (1/mm) to 19.1 (1/mm) (p=0.5), while in the second group, on the contrary, it had tendency to decrease from 18.6 (1/mm) to 17.9 (1/mm) (p=0.63). In the deep vascular plexus, the density of the vascular bed trended to decrease in both groups, but in group 2 (42.5% and 42.4%, p=1.0) it was more pronounced than in the first group (42.5% and 42.6%, p=0.82). However, the fractal dimension of the vascular bed increased in group 1 (21.0 (1/mm) and 21.3 (1/mm), p=0.43) and showed a slight tendency to decrease in group 2 (21.5 (1/mm) and 21.0 (1/mm), p=0.86).

CONCLUSION

The general trend of changes in hemodynamic parameters demonstrates a potential positive effect, especially in the data related to the deep vascular plexus.