The effect of physical effort on retinal activity in the human eye: rod and cone flicker electroretinogram studies

Effects of voluntary and forced physical exercise on the retinal health of aging Wistar rats

Aging is accompanied by an increased prevalence of degenerative conditions, including those affecting ocular health, which significantly impact quality of life and increase the burden on healthcare systems. Among these, retinal aging is of particular concern due to its direct link to vision impairment, a leading cause of disability in the elderly. Vision loss in the aging population is associated with heightened risks of cognitive decline, social isolation, and morbidity. This study addresses the critical gap in our understanding of modifiable lifestyle factors, such as physical exercise, that may mitigate retinal aging and its related pathologies. We investigated the effects of different exercise regimens-voluntary (recreational-type) and forced (high-intensity)-on the retinal health of aging Wistar rats (18-month-old), serving as a model for studying the translational potential of exercise interventions in humans. Male Wistar rats were divided into four groups: a young control (3-month-old) for baseline comparison, an aged sedentary control, an aged group engaging in voluntary exercise via a running wheel in their cage, and an aged group subjected to forced exercise on a treadmill for six sessions of 20 min each per week. After a 6-month experimental period, we assessed retinal function via electroretinography (ERG), measured retinal thickness histologically, and analyzed protein expression changes relevant to oxidative stress, inflammation, and anti-aging mechanisms. Our findings reveal that voluntary exercise positively impacts retinal function and morphology, reducing oxidative stress and inflammation markers while enhancing anti-aging protein expression. In contrast, forced exercise showed diminished benefits. These insights underscore the importance of exercise intensity and preference in preserving retinal health during aging. The study highlights the potential of recreational physical activity as a non-invasive strategy to counteract retinal aging, advocating for further research into exercise regimens as preventative therapies for age-related ocular degenerations.

The Use of the RETeval Portable Electroretinography Device for Low-Cost Screening: A Mini-Review

Electroretinography (ERG) provides crucial insights into retinal function and the integrity of the visual pathways. However, ERG assessments classically require a complicated technical background with costly equipment. In addition, the placement of corneal or conjunctival electrodes is not always tolerated by the patients, which restricts the measurement for pediatric evaluations. In this short review, we give an overview of the use of the RETeval portable ERG device (LKC Technologies, Inc., Gaithersburg, MD, USA), a modern portable ERG device that can facilitate screening for diseases involving the retina and the optic nerve. We also review its potential to provide ocular biomarkers in systemic pathologies, such as Alzheimer's disease and central nervous system alterations, within the framework of oculomics.

Electrophysiological Evidence of Stroboscopic Training in Elite Handball Players: Visual Evoked Potentials Study

Stroboscopic training enhances perceptual cognition and motor skills; however, neurophysiological mechanisms underlying this adaptation are not fully understood. This study aimed to investigate the effects of a six-week stroboscopic training program on the conductivity of the visual pathway in elite handball players, specifically related to their visual processing of retinal location and viewing conditions. The study included 22 handball players who were randomly assigned to an experimental or a control group. Both groups performed handball-specific in-situ tasks, but only the experimental group underwent stroboscopic training. Participants were assessed three times using visually evoked potential recordings measured by P100 implicit time and amplitude under three viewing conditions (dominant eye, non-dominant eye, and binocular) and two retinal locations (extra-foveal and foveal vision) before and after the six-week training period, and again four weeks later. The results showed a significant TIME vs. GROUP effect of P100 implicit time for the dominant eye in extra-foveal vision (F2,40 = 5.20, p = 0.010, ηp2 = 0.206), extra-foveal binocular viewing (F2,40 = 3.32, p = 0.046, ηp2 = 0.142), and dominant eye foveal vision (F2,40 = 4.07, p = 0.025, ηp2 = 0.169). Stroboscopic training significantly improved early visual processing by reducing the P100 implicit time for the dominant eye and binocular vision, particularly in extra-foveal vision. The improvements were more noticeable in the short compared to the long term.

Low-Intensity Exercise in Mice Is Sufficient to Protect Retinal Function During Light-Induced Retinal Degeneration

Purpose

We previously reported that a specific treadmill running exercise regimen protects against light-induced retinal degeneration (LIRD) in mice. We hypothesized that this protective effect varies with running intensity. To test this, mice undergoing LIRD were run at different treadmill speeds and retinal function was assessed.

Methods

BALB/c mice were assigned to LIRD groups at varying treadmill speeds-0, 5, 10, or 20 m/min labeled inactive, low, medium, and high, respectively-and compared with naïve mice exposed to standard lighting (50 lux; naïve). Following 2 weeks of exercise, a subset of mice were exposed to toxic light (10,000 lux; LIRD) for 4 hours. After 5 additional days of exercise, retinal function was assessed by ERG. Corticosterone levels in serum and cathepsin B (CTSB) protein levels in muscle, brain, serum, and retina were measured. The retinal gene expression of complement factor 1qa (C1qa) and CTSB were measured.

Results

The low+LIRD and medium+LIRD exercise groups had greater a- and b-wave ERG amplitudes when compared with the inactive+LIRD group (P < 0.02). The high+LIRD mice only differed from the inactive+LIRD mice in their dark-adapted b-waves. Serum corticosterone increased in the high+LIRD mice (P < 0.006). Retinal CTSB protein levels were higher in the low+LIRD versus high+LIRD mice (P < 0.004) but were otherwise unchanged. Exercise of any intensity decreased C1qa gene expression.

Conclusions

Faster running did not additionally protect against LIRD, but it did increase serum corticosterone, suggesting stress-induced limits to exercise benefits. Unexpectedly, exercise did not increase CTSB proteins levels in muscle or serum, suggesting that it may not mediate exercise effects. Our results have implications for the use of low-intensity exercise as a vision loss treatment.

Effect of a maximal treadmill test on intraocular pressure and ocular perfusion pressure: The mediating role of fitness level

Objectives:

We compared the impact of a maximal treadmill test on intraocular pressure and ocular perfusion pressure between trained and untrained individuals.

Methods:

Based on the maximal aerobic capacity (relative VO2 max), 31 military helicopter pilots were divided into groups of trained (n = 16; VO2 max = 57.06 ± 1.66) and untrained (n = 15; VO2 max = 43.42 ± 1.19) individuals. Intraocular pressure and blood pressure were collected before effort, just after volitional exhaustion and after 5 and 15 min of recovery.

Results:

The maximal treadmill test induced significant changes on intraocular pressure (p < 0.001, η2 = 0.52) and ocular perfusion pressure (p < 0.001, η2 = 0.60). Intraocular pressure and ocular perfusion pressure increased just after volitional exhaustion (effect size = 0.88 and 1.59, respectively), and these values returned to baseline levels after 5 (effect size = 0.87 and 1.26, respectively) and 15 (effect size = 1.23 and 1.91, respectively) min of recovery. The untrained group exhibited higher intraocular pressure and ocular perfusion pressure values in comparison with the trained group just after volitional exhaustion (effect size = 1.43 and 0.11 for intraocular pressure and effect size = 2.81 and 0.96 for ocular perfusion pressure). Five minutes of recovery was insufficient to reach baseline intraocular pressure and ocular perfusion pressure values only for the untrained group (effect size = 0.91 and 0.72, respectively).

Conclusion:

Our findings reveal that fitness level modulates the intraocular pressure and ocular perfusion pressure responses to a maximal treadmill test, being high fitness levels desirable in order to attenuate the impact of maximal efforts on these indices. These outcomes may be of clinical relevance for the management of glaucoma patients or those at risk, although future studies are needed to test these results in a clinical population.