OPTN and open-angle glaucoma: At least 5% of adult-onset POAG cases are caused primarily by rare variants in 1 of 3 genes: MYOC [HGNC:7610], OPTN [HGNC:17142], or TBK1 [HGNC:11584]13 Myocilin is expressed mainly in the trabecular meshwork, and more than 90% of rare variants in MYOC previously associated with POAG are located in the olfactomedin domain.14