International Ophthalmology · 8 authors, 5 centres
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This study in rats found that 28 days of white LED exposure impaired spatial learning and caused degeneration of visual cortex pyramidal neurons. Blue-light-blocking lenses provided partial protection against these functional and structural changes. The findings suggest that chronic LED exposure may harm visual processing and that blue-blocking lenses could offer some mitigation.
**Background:** Light-emitting diodes (LEDs) are increasingly used due to their efficiency, but they emit high-energy blue wavelengths (400–455 nm) that can cause photochemical retinal damage. Such damage may affect retinal ganglion cells and, through retrograde pathways, alter neurons in the primary visual cortex (V1). Blue-light-blocking lenses (BBLs) are marketed to protect against blue light, but evidence on their efficacy in preventing cortical changes is limited. This study investigated the impact of white LED exposure on behavior and V1 layer 5 pyramidal neurons (V1L5PNs) in rats and the potential protective effect of two commercially available BBLs.
**Methods:** Twenty-four adult male 8-week-old Wistar rats were randomly divided into four groups (n=6 each): normal control (NC), white LED exposure (LE), LE with Crizal Prevencia BBL (CP), and LE with Duravision Blue BBL (DB). The LE, CP, and DB groups were exposed to white LEDs at 450–500 lx for 28 days on a 12:12-h dark/light cycle. BBLs were fixed to the LEDs in the treatment groups. After exposure, spatial learning and memory were assessed using the Morris water maze (MWM) over four training days and a memory retention test on day 5. Latency to reach the hidden platform was recorded. Following behavioral testing, brains were harvested and processed with Golgi-Cox stain. A total of 846 V1L5PNs (36 neurons per animal) were imaged, and apical and basal dendritic branching and intersections were quantified using Sholl analysis from 0 to 140 µm from the soma. Statistical analysis used two-way ANOVA with Tukey’s post hoc test.
**Key Results:** Behavioral assessment showed a statistically significant difference in mean latencies across groups (F(3,392)=0.001, p<0.001). Post hoc analysis revealed significant differences on day 1 (p<0.05) and day 2 (p<0.01). The average latency over four training days was 16.38 s for NC, 12.57 s for LE, 15.04 s for CP, and 11.52 s for DB. On the memory retention test, latencies were 19.76 s (NC), 8.6 s (LE), 15.67 s (CP), and 9.53 s (DB). Structural analysis showed a significant reduction in apical branching and intersection points at all distances from the soma in the LE and BBL groups compared to NC (F(18,140)=0.001, p<0.001). Basal branching and intersections also showed significant reduction (F(18,140)=0.019, p<0.001). The DB group had more branching points than NC, LE, and CP groups. These findings indicate that white LED exposure caused degenerative changes in V1L5PNs, and BBLs provided partial protection.
**Clinical Implications:** This study provides evidence that chronic exposure to white LEDs can impair spatial learning and induce structural degeneration in the visual cortex, likely through retrograde degeneration from retinal damage. Blue-light-blocking lenses, particularly Duravision Blue, offered partial functional and structural protection. These findings highlight potential risks of prolonged LED exposure for visual and cognitive health and support the use of BBLs as a protective measure. However, the short exposure period (28 days) and lack of retinal histological assessment are limitations. Future studies with longer exposure and retinal evaluation are needed to clarify the pathway and optimize protective strategies.