The effects of low-color-temperature dual-primary-color light-emitting diodes on three kinds of retinal cells

Therapeutic effects of low-color-temperature light-emitting diodes on dry eye

BACKGROUND

As a new technology for treating dry eye diseases, phototherapy has attracted great attention, but the research on its safety and effectiveness is limited. In this study, the therapeutic effects of low-color-temperature light-emitting diodes on dry eye in humans, rabbits, and rats were investigated.

METHODS

In clinical experiments, subjects in both groups read the same paper for 3 h under light sources of two color temperatures: 1900 K (low-color-temperature light-emitting diodes) or 4000 K (artificial fluorescent white light-emitting diodes). The differences in the non-invasive tear film breakup time, tear meniscus height, and conjunctival congestion scores before and after the experiment were compared between the two groups. In animal experiments, corneal epithelial barrier function and tear production of Sprague-Dawley rats and New Zealand white rabbits with dry eye were compared before and after low-color-temperature light-emitting diodes treatment. TUNEL staining and Western blotting were used to detect the apoptosis of corneal and conjunctival cells and the expression of inflammatory factor IL-1β.

RESULTS

Low-color-temperature light-emitting diodes prolonged tear film breakup time in patients with dry eye. Moreover, it increased tear secretion, decreased fluorescein sodium staining scores, corneal and conjunctival cell apoptosis, and inflammatory factor expression in rabbits and rats with dry eye.

CONCLUSIONS

Low-color-temperature light-emitting diodes phototherapy can be used as an effective treatment for dry eye, reducing its symptoms and related ocular surface damage in humans, rabbits, and rats.

Determination of Correlated Color Temperature in Ex Vivo Porcine Eyes during Intraocular Illumination

(1) Background: In ophthalmic surgery, white light is mostly applied to illuminate the intraocular space, and ophthalmologists are comfortable working with it. Diaphanoscopic illumination changes the spectral composition of light, resulting in a change in the correlated color temperature (CCT) of the intraocular illumination. This color change makes it difficult for surgeons to recognize the structures in the eye. CCT during intraocular illumination has not yet been measured before, and it is the aim of this study to perform such measurement. (2) Methods: CCT was measured inside ex vivo porcine eyes during diaphanoscopic illumination and endoillumination using a current ophthalmic illumination system with a detection fiber inside the eye. By applying pressure on the eye with a diaphanoscopic fiber, the dependency of CCT on pressure was examined. (3) Results: The intraocular CCT values during endoillumination were 3923 K and 5407 K for the halogen and xenon lamps, respectively. During diaphanoscopic illumination, a strong unwanted red shift was observed, resulting in 2199 K and 2675 K for the xenon and the halogen lamps, respectively. Regarding different applied pressures, the CCT did not differ considerably. (4) Conclusions: This red shift should be compensated for in the development of new illumination systems since surgeons are used to white light illumination, which also simplifies the identification of retinal structures.

Antioxidative and Mitochondrial Protection in Retinal Pigment Epithelium: New Light Source in Action

Low-color-temperature light-emitting diodes (LEDs) (called 1900 K LEDs for short) have the potential to become a healthy light source due to their blue-free property. Our previous research demonstrated that these LEDs posed no harm to retinal cells and even protected the ocular surface. Treatment targeting the retinal pigment epithelium (RPE) is a promising direction for age-related macular degeneration (AMD). Nevertheless, no study has evaluated the protective effects of these LEDs on RPE. Therefore, we used the ARPE-19 cell line and zebrafish to explore the protective effects of 1900 K LEDs. Our results showed that the 1900 K LEDs could increase the cell vitality of ARPE-19 cells at different irradiances, with the most pronounced effect at 10 W/m². Moreover, the protective effect increased with time. Pretreatment with 1900 K LEDs could protect the RPE from death after hydrogen peroxide (H₂O₂) damage by reducing reactive oxygen species (ROS) generation and mitochondrial damage caused by H₂O₂. In addition, we preliminarily demonstrated that irradiation with 1900 K LEDs in zebrafish did not cause retinal damage. To sum up, we provide evidence for the protective effects of 1900 K LEDs on the RPE, laying the foundation for future light therapy using these LEDs.

Two-photon absorption behavior of conjugated oligomers suitable for low colour temperature LEDs

Light emitting diodes (LEDs) with low colour temperatures (CTs) have been proved to be physiologically-friendly light sources. However, there are few reports on the photophysical properties of luminescent materials with CTs lower than candlelight. Herein, one- and two-photon optical properties of four fluorenone-based conjugated oligomers have been systemically investigated. By using a sum-over-essential states (SOS) approach, we obtained the transition dipole moments and two-photon absorption (TPA) cross sections. The triphenylamine end-capped oligomer exhibits reddish orange luminescence with extremely low colour temperature of 1686 K, which is much lower than that of candlelight. Fluorene-ethylene units serving as π-spacers could weaken the role of electron-donating units and effectively enhance the TPA performance of oligomers. Our results provide an effective way for the design and optimization of universal light-emitting material candidates in optoelectronic devices.

Luminescence Properties and Energy Transfer of Eu3+, Bi3+ Co-Doped LuVO4 Films Modified with Pluronic F-127 Obtained by Sol-Gel

Nowadays, orthovanadates are studied because of their unique properties for optoelectronic applications. In this work, the LuVO₄:Eu³⁺, Bi³⁺ films were prepared by the sol-gel method, using a new simple route, and deposited by the dip-coating technique. The obtained films are transparent, fracture-free, and homogenous. The sol-gel process was monitored by Fourier-transform infrared spectroscopy (FTIR), and according to X-ray diffraction (XRD) results, the crystal structure was tetragonal, and films that were highly oriented along the (200) low-energy direction were obtained. The morphological studies by scanning electron microscopy (SEM) showed uniformly distributed circular agglomerations of rice-like particles with nanometric sizes. The luminescence properties of the films were analyzed using a fixed concentration of 2.5 at. % Eu³⁺ and different concentrations of Bi³⁺ (0.5, 1.0, and 1.5 at. %); all the samples emit in red, and it has been observed that the light yield of Eu³⁺ is enhanced as the Bi³⁺ content increases when the films are excited at 350 nm, which corresponds to the ¹S₀→³P₁ transition of Bi³⁺. Therefore, a highly efficient energy transfer mechanism between Bi³⁺ and Eu³⁺ has been observed, reaching up to 71%. Finally, it was established that this energy transfer process occurs via a quadrupole-quadrupole interaction.

More light components and less light damage on rats’ eyes: evidence for the photobiomodulation and spectral opponency

The blue-light hazard (BLH) has raised concerns with the increasing applications of white light-emitting diodes (LEDs). Many researchers believed that the shorter wavelength or more light components generally resulted in more severe retinal damage. In this study, based on the conventional phosphor-coated white LED, we added azure (484 nm), cyan (511 nm), and red (664 nm) light to fabricate the low-hazard light source. The low-hazard light sources and conventional white LED illuminated 68 Sprague-Dawley (SD) rats for 7 days. Before and after light exposure, we measured the retinal function, thickness of retinal layers, and fundus photographs. The expression levels of autophagy-related proteins and the activities of oxidation-related biochemical indicators were also measured to investigate the mechanisms of damaging or protecting the retina. With the same correlated color temperature (CCT), the low-hazard light source results in significantly less damage on the retinal function and photoreceptors, even if it has two times illuminance and blue-light hazard-weighted irradiance ([Formula: see text]) than conventional white LED. The results illustrated that [Formula: see text] proposed by IEC 62471 could not exactly evaluate the light damage on rats' retinas. We also figured out that more light components could result in less light damage, which provided evidence for the photobiomodulation (PBM) and spectral opponency on light damage.

VEGF Mediates Retinal Müller Cell Viability and Neuroprotection through BDNF in Diabetes

To investigate the mechanism of vascular endothelial growth factor (VEGF) and brain-derived neurotrophic factor (BDNF) in Müller cell (MC) viability and neuroprotection in diabetic retinopathy (DR), we examined the role of VEGF in MC viability and BDNF production, and the effect of BDNF on MC viability under diabetic conditions. Mouse primary MCs and cells of a rat MC line, rMC1, were used in investigating MC viability and BDNF production under diabetic conditions. VEGF-stimulated BDNF production was confirmed in mice. The mechanism of BDNF-mediated MC viability was examined using siRNA knockdown. Under diabetic conditions, recombinant VEGF (rVEGF) stimulated MC viability and BDNF production in a dose-dependent manner. rBDNF also supported MC viability in a dose-dependent manner. Targeting BDNF receptor tropomyosin receptor kinase B (TRK-B) with siRNA knockdown substantially downregulated the activated (phosphorylated) form of serine/threonine-specific protein kinase (AKT) and extracellular signal-regulated kinase (ERK), classical survival and proliferation mediators. Finally, the loss of MC viability in TrkB siRNA transfected cells under diabetic conditions was rescued by rBDNF. Our results provide direct evidence that VEGF is a positive regulator for BDNF production in diabetes for the first time. This information is essential for developing BDNF-mediated neuroprotection in DR and hypoxic retinal diseases, and for improving anti-VEGF treatment for these blood-retina barrier disorders, in which VEGF is a major therapeutic target for vascular abnormalities.