Key photoreceptor genes such as RLBP1, RDH12, CRABP1, NRL, SOX8, RHO, PAX6, and SAG were significantly low in advanced Rb tumors, compared to non-advanced Rb tumors in RT-PCR analysis (p ≤ 0.05), further confirming the gene expression pattern identified in the tumor microarray (Figure 3C). Here, NRL is linked to retinoblastoma.