opening his mouth is just a way they help get there skin on there head ready to peel for a shed. but the clicking is definitely a sign of RI i would get your BP to a vet as soon as you can for a check up. i would boost up the humidity a tad help him with that shed and then take him to the vet. up the temps a bit too. to help if it is RI. i wouldnt take him to the vet until the have shed as this is a stressful time for them being partially vision impaired. but if he looks like he is becoming rapidly worse i would forgo waiting for the shed and get him in ASAP.