Hello again and thanks for waiting.
I have worked out an answer for you below ...
While I cannot diagnose this over the internet I can talk you through what I would be thinking if I was presented with such a case at my clinic.
Have a look at this image LINK
and see if this looks like your cat has ...
If so this is the third eyelid of the cat and is on the inside corner of the cat's eye and is referred to as the nictitating membrane. It is the same membrane you see in the eyes of birds and snakes but people do not have it. Its function is unclear it may act to clean debris off the eye.
1. In some cats the third eyelid is noticeable but they are perfectly healthy in every other way, in these cases it may be a sign that your cat has recently had exposure to some infection or other but has now recovered.
2. In other cats it may be a sign that they are ill in some way and you may be seeing other symptoms, but it is not a reliable indicator which type of illness your cat may be suffering from. For this reason the wisest thing is that you have your vet check your cat over just to be on the safe side.
3. Where cats are not showing other signs of illness the third eyelid usually goes back to its normal position in a week without any particular treatment.
I hope I have covered your question fully enough but if you would like further clarification or to talk things over a bit more then I will be on-line for the next hour or so and I will be more than pleased to continue working with you.
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