▁to ▁phot ic ▁reg ulation ▁and ▁ac ute ▁phot ic ▁supp ression ▁of ▁release ▁of ▁the ▁h orm one ▁mel aton in . ▁ ▁In ▁r ats , ▁they ▁play ▁some ▁role ▁in ▁conscious ▁visual ▁per ception , ▁including ▁per ception ▁of ▁regular ▁grat ings , ▁light ▁levels , ▁and ▁spatial ▁information . ▁ ▁Phot ore cept ive ▁gang l ion ▁cells ▁have ▁been ▁isolated ▁in ▁humans , ▁where , ▁in ▁addition ▁to ▁reg ulating ▁the ▁circ ad ian ▁rh ythm , ▁they ▁have ▁been ▁shown ▁to ▁medi ate ▁a ▁degree ▁of ▁light ▁recognition ▁in ▁rod less , ▁con eless ▁subjects ▁suffering ▁with ▁dis orders ▁of ▁rod ▁and ▁cone ▁phot ore cept ors . ▁Work ▁by ▁Far han ▁H . ▁Za idi ▁and ▁colle agues ▁showed ▁that ▁phot ore cept ive ▁gang l ion ▁cells ▁may ▁have ▁some ▁visual ▁function ▁in ▁humans . ▁ ▁The ▁phot op ig ment ▁of ▁phot ore cept ive ▁gang l ion ▁cells , ▁mel an ops in , ▁is ▁excited ▁by ▁light ▁mainly ▁in ▁the ▁blue ▁portion ▁of ▁the ▁visible ▁spectrum ▁( abs or ption ▁pe aks ▁at ▁~ 4 8 0 ▁nan om eters ). ▁The ▁phot otr ans du ction ▁mechanism ▁in ▁these ▁cells ▁is ▁not ▁fully ▁understood , ▁but ▁seems ▁likely ▁to ▁res emble ▁that ▁in ▁in verte br ate ▁r hab dom er ic ▁phot ore cept ors . ▁In ▁addition ▁to ▁respond ing ▁directly ▁to ▁light , ▁these ▁cells ▁may ▁receive ▁exc itat ory ▁and ▁in hib itory ▁influ ences ▁from ▁ro