Influence of Light Emitting Diode-Derived Blue Light Overexposure on Mouse Ocular Surface

Abstract

Purpose: To investigate the influence of overexposure to light emitting diode (LED)-derived light with various wavelengths on mouse ocular surface.

Methods: LEDs with various wavelengths were used to irradiate C57BL/6 mice at an energy dose of 50 J/cm2, twice a day, for 10 consecutive days. The red, green, and blue groups represented wavelengths of 630 nm, 525 nm, and 410 nm, respectively. The untouched group (UT) was not exposed to LED light and served as the untreated control. Tear volume, tear film break-up time (TBUT), and corneal fluorescein staining scores were measured on days 1, 3, 5, 7, and 10. Levels of interferon (IFN)-γ, interleukin (IL)-1β, IL-6, and tumor necrosis factor (TNF)-α were measured in the cornea and conjunctiva using a multiplex immunobead assay at day 10. Levels of malondialdehyde (MDA) were measured with an enzyme-linked immunosorbent assay. Flow cytometry, 2'7'-dichlorofluorescein diacetate (DCF-DA) assay, histologic analysis, immunohistochemistry with 4-hydroxynonenal, and terminal deoxynucleotidyl transferase-mediated dUTP-nick end labeling (TUNEL) staining were also performed.

Results: TBUT of the blue group showed significant decreases at days 7 and 10, compared with the UT and red groups. Corneal fluorescein staining scores significantly increased in the blue group when compared with UT, red, and green groups at days 5, 7, and 10. A significant increase in the corneal levels of IL-1β and IL-6 was observed in the blue group, compared with the other groups. The blue group showed significantly increased reactive oxygen species production in the DCF-DA assay and increased inflammatory T cells in the flow cytometry. A significantly increased TUNEL positive cells was identified in the blue group.

Conclusions: Overexposure to blue light with short wavelengths can induce oxidative damage and apoptosis to the cornea, which may manifest as increased ocular surface inflammation and resultant dry eye.

Fig 1

Light emitting diode devices and retaining cages of red light (630 nm) (A), green light (525 nm) (B) and blue light (410 nm) (C).

Fig 2. Tear volume in the untouched (UT), red, green, and blue groups at days 1, 3, 5, 7, and 10.

Fig 3. Tear film break-up time in the untouched (UT), red, green, and blue groups at days 1, 3, 5, 7, and 10.

* P < 0.05 compared between groups. ^† P < 0.05 compared with the day 1 value. ^‡ P < 0.05 compared with the day 3 value.

Fig 4

Corneal fluorescein staining scores (A) and representative figures (B) in the untouched (UT), red, green and blue groups at day 1, 3, 5, 7, and 10. * P < 0.05 compared between groups. ^† P < 0.05 compared with the day 1 value. ^‡ P < 0.05 compared with the day 3 value.

Fig 5. Periodic acid Schiff stains of representative conjunctival specimens in the untouched (UT), red, green, and blue groups at day 10.

Fig 6

Flow cytometry showing CD4+CCR5+ T cells in the cornea (A) and conjunctiva (B) of the untouched (UT), red, green, and blue groups at day 10.

Fig 7

Representative images for Terminal dUTP nick-end labeling (TUNEL) assay showing the apoptotic cells in the cornea of the untouched (A, B, C), red (D, E, F), green (G, H, I), and blue (J, K, L) groups at day 10.