Search Results (4)

Purpose: This study was conducted to assess retinal responses in myopic and non-myopic participants after exposure to repeated low-level red-light therapy (RLRT) of 3 min and 1 min duration to see if response differs with exposure time and refractive status using global flash multifocal electroretinogram (gf-mfERG). Methods: This was a prospective exploratory pilot study with a convenient sample of 20 participants of mean age of 25.5 years (18 to 39 years) who underwent 3 min therapy, followed by, 1 week after, 1 min therapy in each participant between February to May 2025. However, four participants who did not appear in 1 min therapy for measurements were excluded from the between-group comparison analysis. We measured retinal responses using gf-mfERG ring-wise implicit time (DCT, ICT) and amplitude (DCA, ICA), baseline, post-first and post-second RLRT. Data analysis included descriptives, repeated measures ANOVA, post hoc test, Bonferroni adjusted correction, and correlation with axial length (AL) and choroidal thickness (CT) in each group. The study was conducted at CEORLab, University of Minho, Portugal, and adhered to Ethical Committee approval and the tenets of the Declaration of Helsinki. Results: In 3 min RLRT exposure, no significant within-subject changes were observed across direct (DC) and induced (IC) gf-mfERG components across all rings (p > 0.05). Statistically significant between-group differences in DC implicit time were noted in Ring 2 (p = 0.029) and Ring 3 (p = 0.012). IC amplitude showed significant within-subject changes in myopes (Ring 1: p = 0.030; Ring 4: p = 0.035) and non-myopes (Ring 1: p = 0.042; Ring 3: p = 0.001; Ring 4: p < 0.001; Ring 5: p = 0.034), with no significant between-group differences (p > 0.05). In contrast, 1 min RLRT showed no significant changes in DC, IC time or amplitudes ICA, DCA (all p > 0.05). Correlation analysis after 3 min RLRT showed that in myopes, DCT positively correlated with AL in Ring 3 (r = 0.591, p = 0.006) and Ring 4 (r = 0.615, p = 0.004), ICT positively correlated with CT in Ring 2 (r = 0.601, p = 0.005) and Ring 3 (r = 0.573, p = 0.008), and ICA negatively correlated with AL in Rings 3–5 (all p < 0.01). Non-myopes demonstrated limited correlations, including a negative association between ICT and axial length in Ring 4 (r = −0.619, p = 0.004). Similar but weaker patterns were observed following 1 min RLRT. Conclusions: 3-min RLRT induces localized inner retinal functional changes without significantly altering outer retinal responses, while 1-min exposure shows no measurable effect. Retinal ERG responses are primarily influenced by axial length, particularly in myopic eyes, highlighting a structure–function relationship rather than a robust short-term therapeutic effect of RLRT. Full article

Background: Low-level red-light therapy (RLRT) has emerged as a potential therapy in myopia management. However, its effects on retinal structure and function following repeated exposure remain incompletely understood. Purpose: To evaluate the short-term effects of RLRT on central retinal function in myopes and non-myopes using retinal electrophysiology and structural parameters. Methods: Thirty-six subjects underwent RLRT exposures. Retinal function was assessed using pattern electroretinography (PERG) and photopic full-field electroretinography (Photopic 3.0 ERG). Structural measurements, including axial length (AL), obtained with an optical biometer and choroidal thickness (CT), were measured using MOPTIM 3000. Outcomes were compared between baseline and post-RLRT conditions (single 3 min and single 1 min exposure), across refractive groups, and correlated with AL and CT. This study was conducted at the University of Minho in accordance with the Declaration of Helsinki. Results: In myopic subjects, PERG N35–P50 amplitude significantly increased after 3 min of RLRT (baseline:0.88 ± 0.21 µV; post: 1.40 ± 0.25 µV; p = 0.013), whereas no significant changes were observed in non-myopes (baseline: 1.32 ± 0.19 µV; post: 1.39 ± 0.21 µV; p = 0.47). Latencies remained stable across all groups (p > 0.05). No significant correlations were found between PERG and AL (ρ = −0.18, p = 0.44) or CT (ρ = 0.12, p = 0.52). Photopic 3.0 ERG showed an increase in b-wave amplitude after 3 min of RLRT in myopes (Δ = +2.42 µV, p = 0.06), but not in non-myopes. In myopes, AL was negatively correlated with post-therapy latency (ρ = −0.624, p = 0.060), while CT showed strong correlations with photopic a-wave responses after 1 min RLRT (CT vs. latency: ρ = −0.873, p = 0.010; CT vs. amplitude: ρ = 0.821, p = 0.034). Conclusions: Short-term exposure to RLRT, particularly at 3 min, enhances PERG and Photopic ERG responses in myopic subjects, suggesting transient improvements in retinal function with differential effects between refractive groups. Full article

Spectrum Sensing (SS) is expected to play a crucial role in forthcoming 6G Cognitive Radio Networks (CRNs), where unlicensed users will be able to dynamically access the spectrum and perform opportunistic transmissions without generating interference for licensed users. In this work, we investigate multiple-antenna SS techniques by analyzing the performance of several widely used detection schemes—namely, Roy’s Largest Root Test (RLRT), the Generalized Likelihood Ratio Test (GLRT), the Eigenvalue Ratio Detector (ERD), and the Energy Detector (ED)—under varying false-alarm probabilities and signal-to-noise ratios (SNRs). We assume there are a fixed number of sensors at the secondary-user receiver, namely, four. To evaluate the behavior of these detectors in realistic conditions, we developed a software-defined radio (SDR) testbed using Universal Software Radio Peripherals (USRPs), enabling both primary-user signal transmission and secondary-user data acquisition. The experimental results, illustrated through Receiver Operating Characteristic (ROC) and performance curves, are compared with simulation outcomes. The analysis is complemented by a detailed state-of-the-art listing of the available analytical characterizations of the false-alarm probabilities for the considered SS schemes. In particular, the GLRT false-alarm probability, previously unavailable in explicit form for a four-antenna equipped receiver, is computed as well. These results validate the superior detection capability of RLRT over the other schemes tested, confirming its effectiveness not only in theoretical analysis but also in practical SDR-based implementations. Full article

In cognitive radio (CR) networks, eigenvalue-based detectors (EBDs) have attracted much attention due to their good performance of detecting secondary users (SUs). In order to further improve the detection performance of EBDs with short samples, we propose two new detectors: average circulant matrix-based Roy’s largest root test (ACM-RLRT) and average circulant matrix-based generalized likelihood ratio test (ACM-GLRT). In the proposed method, the circulant matrix of samples at each time instant from SUs is calculated, and then, the covariance matrix of the circulant matrix is averaged over a short period of time. The eigenvalues of the achieved average circulant matrix (ACM) are used to build our proposed detectors. Using a circulant matrix can improve the dominant eigenvalue of covariance matrix of signals and also the detection performance of EBDs even with short samples. The probability distribution functions of the detectors undernull hypothesis are analyzed, and the asymptotic expressions for the false-alarm and thresholds of two proposed detectors are derived, respectively. The simulation results verify the effectiveness of the proposed detectors. Full article