The retinas of many species show regional specialisations that are evident in the differences in the processing of visual input from different parts of the visual field. Regional specialisation is thought to reflect an adaptation to the natural visual environment, optical constraints, and lifestyle of the species. Yet, little is known about regional differences in synaptic circuitry. Here, we were interested in the topographical distribution of connexin-36 (Cx36), the major constituent of electrical synapses in the retina. We compared the retinas of mice, rats, and cats to include species with different patterns of regional specialisations in the analysis. First, we used the density of Prox1-immunoreactive amacrine cells as a marker of any regional specialisation, with higher cell density signifying more central regions. Double-labelling experiments showed that Prox1 is expressed in AII amacrine cells in all three species. Interestingly, large Cx36 plaques were attached to about 8–10% of Prox1-positive amacrine cell somata, suggesting the strong electrical coupling of pairs or small clusters of cell bodies. When analysing the regional changes in the volumetric density of Cx36-immunoreactive plaques, we found a tight correlation with the density of Prox1-expressing amacrine cells in the ON, but not in the OFF sublamina in all three species. The results suggest that the relative contribution of electrical synapses to the ON- and OFF-pathways of the retina changes with retinal location, which may contribute to functional ON/OFF asymmetries across the visual field.

Traumatic brain injury (TBI) induces complex molecular and cellular responses, often leading to vision deterioration and potential mortality. Current objective diagnostic methods are limited, necessitating the development of novel tools to assess disease severity. This review focuses on the retina, a readily approachable part of the central nervous system (CNS), as a potential indicator of TBI. We conduct a targeted database search and employ a blinded scoring system, incorporating both human and artificial intelligence (AI) assessments, to identify relevant articles. We then perform a detailed analysis to elucidate the molecular pathways and cellular changes in the retina following TBI. Recent findings highlight the involvement of key molecular markers, such as ionized calcium-binding adapter molecule 1 (IBA1), phosphorylated tau, glial fibrillary acidic protein (GFAP), and various cytokines (IL-1β, IL-6, and TNF). Additionally, the roles of oxidative stress, reactive oxygen species (ROS), and blood–retina barrier (BRB) disruption are explored. Based on these findings, we hypothesize that alterations in these molecular pathways and cellular components, particularly microglia, can serve as direct indicators of brain health and TBI severity. Recent technological advancements in retinal imaging now allow for a direct assessment of retinal cells, including microglia, and related inflammatory processes, facilitating the translation of these molecular findings into clinical practice. This review underscores the retina’s potential as a non-invasive window into the molecular pathophysiology of TBI.

Traumatic brain injury (TBI) represents a significant medical concern typically resulting from severe or repetitive mild head impacts. It often results in vision deterioration and can cause sudden death after hospitalization as a result of pathologies. The objective identification options are limited or too invasive to be routinely applied; therefore, we need new tools to identify the severity of the disease. The retina is the only part of the central nervous system that is directly approachable by light and easy to access. In this review, we used an aimed database search, together with a blinded human and artificial intelligence (AI) based scoring system to narrow down the number of articles, based on relevance to the topic. The selected articles went through thorough processing to identify the relevant links in them. Based on this, we hypothesize that the retina can be used as a direct indicator of brain health, including the use of microglia to indicate traumatic brain injury. As an outcome, we concluded that recent developments in technology now allow the imaging of the retinal surface and cells directly to allow retinal cellular and inflammatory assessment and translation of the findings into medical practice.

Glucose monitoring (GM) neurons of the hypothalamus are important in the regulation of feeding and metabolism. We have shown recently that streptozotocin (STZ) administration into the ventromedial hypothalamus (VMH) elicits selective destruction of specific GM neurons causing severe deficits of feeding and metabolism. STZ is selectively toxic to cells expressing the type-2 glucose transport protein GLUT2. This transporter was first found in pancreatic b-cells, and it is mainly localized to GM neurons in the brain. In the present study, we were interested whether STZ microinjections into the VMH cause loss of hypothalamic GLUT2 immunolabeling in the rat. Young adult male rats (n=3) were bilaterally microinjected with 0.75 µl 0,0037 M STZ into the VMH. Rats injected with physiological saline and untreated animals served as controls (n=4). Histological sections of brain and pancreas were immunolabeled with GLUT2-specific antibodies after 48h survival. We found a massively reduced GLUT2 immunolabeling in the periventricular hypothalamic nuclei in brains of STZ-microinjected animals without any difference in immunopositivity of pancreatic β-cells against controls. Our preliminary results suggest that the metabolic and behavioral changes following hypothalamic STZ injections can be explained by a selective destruction of GLUT2-expressing neurons of the GM network.

Background and Objectives: Visual impairment and reduced stereovision significantly impact the quality of life and increase fall risk in older adults. While standard clinical assessment of visual functions is essential in this population, its use is often limited by the need for specialized equipment and trained personnel. Tablet-based screening tools offer a practical alternative but require clinical validation. This study aimed to assess the agreement, reliability, and diagnostic performance of a tablet-based screening application (index methods) compared to established clinical reference methods for assessing visual acuity (VA) and stereovision (SV) in adults over 60 years. Materials and Methods: This prospective, non-blinded, cross-sectional, feasibility study included two cohorts: a test–retest group of 24 older adults assessed twice within 7 days, and a clinical cross-sectional group of 135 participants recruited from primary care practices. VA was measured using tablet-based Landolt C test and compared with an ETDRS-style chart, while stereovision was assessed using tablet-based static and dynamic random dot stereograms and compared with the TNO stereotest. Agreement and reliability were evaluated using Bland–Altman analysis, intraclass correlation coefficients (ICC), and receiver operating characteristic (ROC) curves. Results: The index VA method demonstrated good test–retest reliability (ICC = 0.79) with no significant difference between repeated measurements. In the clinical cross-sectional group, visual acuity measurements showed a small mean bias (0.022 logMAR) between the index and reference methods, which remained within clinically acceptable limits, particularly in the intermediate acuity range. For stereovision, the index SV tests showed high test–retest agreement. Using a TNO cutoff of 480 arcsec, the index SV method demonstrated good diagnostic accuracy (AUC 0.87 for static and 0.85 for dynamic stimuli) with high sensitivity for detecting impaired stereovision. Conclusions: The tablet-based index method provided reliable and clinically comparable results for VA and SV assessments in older adults, supporting its potential use as a screening tool in primary care and community-based settings.