My cat has an exposed inner eyelid, only left eye, the eyelid

Hello, my name is***** and I have over 20 years of experience as a veterinarian. I am sorry to hear about your fellow's raised left eye third eyelid, waxy left ear and inflammation around his tooth.
The third eyelid is a protective eyelid that can rise up in response to irritation in the eye such as a foreign body, getting an irritant sprayed in his eyes, a scratch on the cornea (clear outer part of the eye) or an upper respiratory infection. In these cases you will see a discharge from the eye, clear, yellow or green, redness of the white around the eye and sometimes the kitty will rub the eye.
But it can also rise up secondary to a syndrome called Horner's Syndrome. This is secondary to irritation of the nerve that innervates the upper eyelid, some eye muscles as well as the third eyelid. In these cases the eye may look sunken as well and the pupil will be smaller in the eye then normal. See this picture:
http://4.bp.blogspot.com/-M-gG_XiF814/TzFbBPfYFjI/AAAAAAAAAnc/Axthh-it6N8/s320/Horners_syndrome.jpg
If both eyes were affected it could be secondary to intestinal irritation or parasites. In that case there won't be any discharge, the kitty will be bright and normal otherwise and treating the intestinal upset or parasites will cause the eyelids to return to normal in several week's time.
If the tooth that you are speaking of is a molar tooth, very far back in the mouth it is possible that his other symptoms could be related to an abscessed/infected tooth root.
But if the tooth is in the front of the mouth this is less likely.
In that case it is more likely that his raised third eyelid is related to an ear infection or an ear polyp, either from being traumatized when he rubs his ear or due to inflammation in the ear canal affecting the nerves to his eyelid as they pass by his inner ear canal.
Either way your fellow should be seen by his veterinarian to look at his eye and ear and determine how best he should be treated or if further diagnostic testing should be performed.
Please let me know if you have any further questions.