GSTM1 and glaucoma: Flicker light stimulation increased the Hb concentration (Table 1) significantly in the controls (+ 1.3 ± 3.6, p = 0.048) as well as in the rim of glaucoma discs (+ 2.6 ± 5.0, p = 0.006); in the excavation, the increase was non-significant (+ 1.4 ± 4.1, p = 0.101).