Figure 2. The effect of serum deprivation and filtered light on viability of cultured RGC-5 cells. Cells were incubated in normal culture conditions in the presence (red bars) or absence (empty bars) of 10% (v/v) serum and in the presence or absence of light of intensity 1000 lux, as shown for A 24 h or B 48 h. After treatment, the MTT reduction assay was used to determine the level of cell survival, compared with controls. Serum deprivation caused a small but significant reduction in culture viability, as compared with cells incubated with serum in the dark. This effect was independent of the time of incubation (24 or 48 h). Furthermore, filtered light itself caused a significant reduction in cell viability, but only after 48 h. The toxic effects of both the light treatment and the serum deprivation were additive after 48 h. Statistical analysis using the one-way ANOVA followed by a post-hoc Bonferroni test and comparing with controls incubated in the dark for the same length of time in the presence of serum (n=10), showed significance levels denoted as follows: *p <0.05, ** p <0.01, ***p <0.001.