Phosphodiesterase 5 (PDE5) inhibitors, commonly used in the treatment of erectile dysfunction, may cause ophthalmic complications, mainly non-arteritic ischemic optic neuropathy (NAION) [132], but only one case of triggering of LHON as a result of using a PDE5 inhibitor, has been reported, which is of very little significance compared to the millions of users worldwide [133]. Here, PDE5A is linked to Leber hereditary optic neuropathy.