To assess if STI1 may be a co-modifier gene interacting with WDR36 to affect the severity of the glaucoma phenotype, we screened for variations in each exon and flanking introns of the STI1 gene in a minimum of 118 POAG patients carrying WDR36 variations (data not shown), and in 75 individuals with no WDR36 variation (20 NTG patients and 55 normal controls); additional information from partially-tested samples was included where the data were of sufficient quality to analyze. The gene discussed is WDR36; the disease is glaucoma.