Research Article

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

Figure 3

Effect of 670 nm light treatment on ONL thickness ratios. (a) Histograms showing mean ONL : retinal thickness ratios for three light damage protocols (750 lux/“low” intensity; 1000 lux/“moderate” intensity; 1500 lux/“high” intensity), summarizing the effects of four different treatment protocols. Following “low level” light (750 lux) damage ONL thickness is greater in the 670 nm light treated animals compared to controls (light damage only). Following “moderate” intensity (1000 lux) light damage, 9, 18, and 36 J/cm2 670 nm pretreated eyes have a significantly thicker ONL compared to controls, while those treated with 90 J/cm2 are not significantly different from untreated controls. Following “high” intensity light damage only treatment with 670 nm light at 90 J/cm2 preserves ONL thickness. ((b) and (c)) Retinal thickness ratios in animals treated with 9 or 18 J/cm2 670 nm light are similar to controls, except at the superior edge (sample S1). (d) Retinal thickness ratios in animals treated with 36 J/cm2 670 nm light demonstrated no significant differences from controls. (e) Retinal thickness ratios in animals treated with 90 J/cm2 670 nm light were significantly greater in the region surrounding the optic nerve head (S4 and I4) compared with controls ( animals 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). ON: optic nerve.
(a) Mean ONL thickness ratios
(b) ONL thickness ratios after 1500-lux light damage
(c) ONL thickness ratios after 1500-lux light damage
(d) ONL thickness ratios after 1500-lux light damage
(e) ONL thickness ratios after 1500-lux light damage