This sort of white – in the third eyelid and also in the cornea of both eyes as you can see here, can only really be lipid. I joking asked in my history how long they had been feeding the tortoise chocolate, only to be told that it had a passion for digestive biscuits not chocolate! I guess over its long life the fat in these has led to these ocular lipid deposits. I daren’t think what its arteries look like!