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

Figure 2

Representative images of the effects of 670 nm light treatment on photoreceptor cell death induced by exposure to different intensities of white light. Images were all taken from the same area in the superior portion of the retina. ((a)–(e)) 750-lux light damage. TUNEL counts were highest in light damage controls with a reduction in TUNEL+ cells seen in retinas that underwent 9 and 18 J/cm² 670 nm light treatment. There were no visible changes between the control and 36 J/cm² treatments but an increase was seen in the 90 J/cm² treatments. ((f)–(j)) 1000-lux light damage. Similar to the 750-lux paradigm, TUNEL counts were highest in light damage controls with a reduction in TUNEL+ cells seen in retinas that underwent 9 and 18 J/cm² 670 nm light treatment. No visible differences were seen between the control and 36 J/cm² treatments. Treatments with a dose of 90 J/cm² 670 nm light appeared to increase the amount of TUNEL+ cells in the ONL. ((k)–(o)) 1500-lux light damage. All retinas stained positive with a high amount of TUNEL cells with only 90 J/cm² treatments appearing to reduce TUNEL+ cell counts (scale bars indicate 50 μm; BBZ is a bisbenzimide stain).

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