Neuroprotection in glaucoma-electrophysiology

Visual Neuroprosthesis - Stimulation of Visual Cortical Centers in The Brain. Design of Non-Invasive Transcranial Stimulation of Functional Neurons

PURPOSE

The purpose of the article is to present the history and current status of visual cortical neuroprostheses, and to present a new method of stimulating intact visual cortex cells.

METHODS

This paper contains an overview of the history and current status of visual cortex stimulation in severe visual impairment, but also highlights its shortcomings. These include mainly the stimulation of currently damaged cortical cells over a small area and, from a morphological point of view, possible damage to the stimulated neurons by the electrodes and their encapsulation by gliotic tissue.

RESULTS

The paper also presents a proposal for a new technology of image processing and its transformation into a form of non-invasive transcranial stimulation of undamaged parts of the brain, which is protected by a national and international patent.

CONCLUSION

The paper presents a comprehensive review of the current options for compensating for lost vision at the level of the cerebral cortex and a proposal for a new non-invasive method of stimulating the functional neurons of the visual cortex.

OCT angiography, RNFL and the visual field at different values of intraocular pressure

The aim of the present study was to investigate the relationship between intraocular pressure (IOP), vessel density (VD), retinal nerve fiber layer (RNFL) parameters and overall defect (OD) of the visual field in eyes where antiglaucoma treatment had not yet been initiated. A total of 61 subjects (122 eyes) who had an IOP of >20 mmHg on several occasions, in at least one eye, in routine outpatient care were included. These were subjects who had never been treated for hypertension glaucoma. The cohort was divided into four subgroups. In the first group, there were 18 eyes with an IOP value of <20 mmHg. In the second group, there were 39 eyes with IOP values of 20-22 mmHg. The third group consisted of 32 eyes with IOP values of 22-24 mmHg and the final group consisted of 33 eyes with IOP values of >24 mmHg. The IOP results were compared with VD, RNFL and OD using Pearson's correlation coefficient to assess the relationship between the selected parameters. RNFL and OD were moderately correlated only in the group of eyes with an IOP value >24 (r=0.48); in the other groups the correlation was very weak. However, changes in visual field were already observed in eyes with IOP 20-22 mmHg (r=-0.27). There was a moderate correlation in eyes with an IOP value >24 mmHg (r=-0.53). The most significant result observed was the relationship between VD and RNFL. In eyes with an IOP value ≤20, a moderate to strong correlation between these parameters was observed. This relationship increased with increasing IOP values up to a very strong correlation in the group with an IOP value >24 mmHg. A moderate to strong dependence between VD and RNFL in eyes with an IOP value ≤20 mmHg was observed, and this dependence was very strongly correlated in the eyes with an IOP value >24 mmHg.

HIGHLIGHTS OF HYPERTENSIVE AND NORMOTENSIVE GLAUCOMA

The paper presents the up-to-date overview of pathogenesis, functional and structural changes in normotensive glaucoma (NTG) and its differences from hypertensive glaucoma (HTG). The autors point out new facts that distinguish both diagnostic groups. In the first place are the results of OCT angiography, which verify the pathology of NTG to the anterior part of optic nerve. Our findings confirmed that vascular component (VD) is more involved in changes of visual field than in perfusion parameters, especially in arteria ophtalmica (AO). Perfusion in arteria centralis retinae (ACR) does not play a significant role in NTG changes in the visual field. VD has very little effect on changes in visual field in HTG. Similarly, the retinal nerve fiber layer (RNFL) for changes in the visual field. Howerver, VD is moderately influenced by changes in RNFL. It should be emphasized that we compared the sum of sensitivity in the central part of the visual field (0-22 degrees) with RNFL and VD. In NTG, the anterior part of the optic nerve is altered. Mainly VD contributes to visual filed changes in NTG. It is also important to note that when the intraocular pressure (IOP) increased above 20 mm Hg, the macular and papillary VD was significantly reduced. Antiglaucomatous treatment with prostaglandins and beta-blockers is essential for the reduction of IOP in HTG. This reduction shoud be bellow 20 mm Hg, in eyes with thinner cornea the decrease in IOP should be more pronounced. It does not matter which antiglaucoma treatment was used. However, it should be noted that prostaglandins have a greater effect on disease progression, but the greater protective effect on the visual field have beta-blockers. Neuroprotectives should be recommended systemically in patients with HTG. When treating NTG, it is important to maintain blood flow of the posterior pole of the eye, but mainly of the anterior part of the optic nerve. Prostaglandins are not suitable in NTG patients, although their effect on IOL reduction is high. Beta-blockers (betaxolol and carteol) and brimonidine are most suitable. Corneal thickness has no effect on disease progression.

OCT ANGIOGRAPHY, VISUAL FIELD AND RNFL WITH VARIOUS MEDICATIONS IN HYPERTENSIVE GLAUCOMAS

AIM

The aim of the study was to determine whether hypertensive glaucoma (HTG) with different types of treatment leads to significant damage in any of the evaluated parameters.

SAMPLE AND METHODOLOGY

The sample, consisting of 36 HTG patients (72 eyes), was divided into three subgroups: In the first group, patients were treated with combination therapy (latanoprost + timolol, latanoprost + dorzolamide + timolol, dorzolamide + timolol). The group consisted of seven women and five men, with an average age of 64 years (49-81). In the second group, patients were treated with beta-blockers (carteolol, betaxolol, timolol). The group consisted of five women and five men, with an average age of 62 years (27-77). In the third group, patients were treated with prostaglandins (latanoprost, bimatoprost). The group consisted of eleven women and three men, with an average age of 61 years (61-78). Criteria for inclusion in the study were visual acuity of 1.0 with a possible correction of less than ±3 dioptres, approximately the same changes in the visual fields of all patients, an intraocular pressure (IOP) of less than 18 mmHg, and no other ocular or neurological disease. The retinal nerve fibre layer (RNFL) on the optic nerve target and vessel density (VD) was measured using an Avanti RTVue XR from Optovue. We determined the values of VD in whole image (WI) and VD of peripapillary (PP). In both cases, we then measured all vessels (VDa) and small vessels (VDs). The visual field was examined by means of a fast threshold glaucoma program with a Medmont M 700 instrument. In addition to the sum of sensitivities in apostilbs (asb) in the range of 0-22 degrees, the overall visual field defect (OD) was also evaluated. The statistical analysis was carried out using a multivariate regression model with adjustment for age and gender. The measured values of the third group were taken as baseline.

RESULTS

In the statistical analysis, we have found differences in visual field in the combination treatment group (p = 0.0006) and differences were recorded for RNFL in the beta-blocker group (p = 0.04).

OCT ANGIOGRAPHY AND DOPPLER ULTRASOUND IN HYPERTENSION GLAUCOMA

AIMS

The main aim of this work was to find out if there is a correlation between vessel density (VD) and results of measured perfusion values in ophthalmic artery and in central retinal artery of the same eye in a group with hypertension glaucoma (HTG).

MATERIALS AND METHODS

The file included 20 patients with HTG, thereof 13 women of average age 68.7 years (49-80 years) and 7 men of average age 58.4 years (27-81 years). Criteria for inclusion in the study: visual acuity 1,0 with possible correction less than ±3 diopters, approximately the same changes in visual fields in every patient, intraocular pressure (IOP) less than 18 mmHg, no other ocular or neurological diseases. VD was measured by Avanti RTVue XR by Optovue firm, perfusion parameters were measured using Doppler ultrasound with Affinity 70G machine by Philips firm. The peak systolic velocity (PSV) and end diastolic velocity (EDV) and resistance index (RI) were measured both in ophthalmic artery (AO) and in central retinal artery (CRA). Visual field (VF) was examined by quick threshold glaucoma program by Medmont M 700 machine. The sum of sensitivities in apostilbs (abs) was evaluated in the range 0-22 degrees of visual field. The results of sensitivities in visual field were compared to VD and perfusion parameters in CRA and AO of the same eye.

RESULTS

Pearsons correlation coefficient (p = 0,05) was used to assess the dependency between chosen parameters. By comparing VF and VD from measured areas, strong correlation (r = 0.64, resp. 0.65) was revealed. It was then proved that VD (WI-VDs) correlates with RICRA weakly (r = -0.35) and moderately strongly (WI-VDa r = -0.4, PP-VDs r = -0.43 and PP-VDa r = -0.45). This means that with increasing resistance index in CRA the density in VD decreases. The other correlations between VD and perfusion parameters (PSV and EDV) in CRA and AO were not significant.

CONCLUSION

Measured values showed that the vascular component of VD has a huge impact on the changes in visual fields in HTG. Weak to moderate influence exists between VD and RI in CRA. OCTA has proven to be more suitable than Doppler ultrasound for determining the condition of blood circulation in the eye.