A Variable Light Emitting Diode (LED) Alternating Between White And Red Light Is Less Toxic Than Constant White Light To Retinal Pigment Epithelial Cells

Abstract

Purpose: : To evaluate the toxicity of retinal pigment epithelial cells in vitro when exposed to a constant white light and an alternating white and red light using a variable LED light source.

Methods: : ARPE-19 retinal pigment epithelial (RPE) cells were seeded onto 96-well plates and grown to confluence. An optical power meter was used to measure the light intensity. Cells were exposed to light emitted from an LED light source for two hours. Using a computer program controlling the LED, the cells were exposed to variable proportions of white and red light at constant white, 1:1, and 1:2 ratios. 24 hours after the exposure period, the cells in the wells were assayed for cell viability using a CellTiter 96 Aqueous One Solution cell proliferation assay. Cells not exposed to the LED light source were used as a control. The experiment was performed in quadruplicate wells for each condition, and repeated on three separate occasions.

Results: : The white light had a 20 mW/cm2 intensity. Cells exposed to constant white light from the LED were 70% as viable as untreated control cells. When cells were exposed to alternating white and red light at a 1:1 proportion, 78% (p = 0.04) remained viable. Decreasing the proportion of white to red light (1:2) further increased cell viability to 88% (p = 0.03).

Conclusions: : Cycling red light with white light is less toxic than constant white light to ARPE-19 cells. Using our variable LED light source and software, the white and red light can be cycled at a frequency higher than that which can be detected by the human retina. LED technology, therefore, may have wide applications in surgical ophthalmic light sources by cycling white and red light at a high enough frequency such that the red light would not be detectable by the surgeon or that computer mediated image processing could eliminate any surgeon perceived image flickering, while reducing the potential for light toxicity to the fundus.

Keywords: retinal pigment epithelium • retina • radiation damage: light/UV