Efficacy of 670 nm Light Therapy to Protect against Photoreceptor Cell Death Is Dependent on the Severity of Damage

Figure 1

Effects of 670 nm light treatment on photoreceptor cell death induced by exposure to different intensities of white light. (a) Dose-response curves for 670 nm light showing the impact on photoreceptor death in “low” (750 lux), “moderate” (1000 lux), and “high” (1500 lux) intensity light damage (LD) paradigms. The highest dose of red light (90 J/cm²) increases levels of photoreceptor death in the low and medium intensity light damage paradigms but protects photoreceptors from cell death in high intensity bright light conditions. Panels (b)–(d) depict the percentage change of TUNEL+ cell count in the retina between the four 670 nm light treatment groups when compared to the light damage only controls. (b) 750 lux: doses of 9 and 18 J/cm² 670 nm light significantly reduced the number of TUNEL+ cells in the ONL compared to the light damaged controls. However, there was no change in the TUNEL+ cell count in retinas treated with 36 or 90 J/cm² 670 nm light ( for each group). (c) 1000 lux: doses of 9 and 18 J/cm² significantly reduced the number of TUNEL+ cells compared to controls, while a dose of 36 J/cm² showed no difference in comparison to controls. Animals treated with 90 J/cm² had a significant increase in TUNEL+ cells in the ONL compared to the light damaged controls ( for each group). (d) 1500 lux: doses of 9, 18, or 36 J/cm² 670 nm light had no significant effect on the numbers of TUNEL+ cells, compared to controls, while treatment with 90 J/cm² 670 nm light significantly reduced the numbers of TUNEL+ cells in the ONL ( for control and 9 J/cm²; animals for 18 J/cm²; for 36 J/cm² and 90 J/cm² groups) (“”denotes significance ; error bars represent SEM).

(a) Dose-response curves

(b) 750 lux (TUNEL)

(c) 1000 lux (TUNEL)

(d) 1500 lux (TUNEL)