I will keep this very short because I only want to say one thing about the cat who has thin fur above the eyes. Quite a few people search for this, looking for answers. It is not possible to provide a complete answer unless you are a veterinarian and the cat is in your presence. However, in my estimation, people who search for information about why their cat has thin hair above the eyes are referring to something that is normal and unrelated to health. The coat immediately above the eyes is, in my experience, more sparse in terms of hair strand density, than any other part of the body except the tips of the ears.
So if you are searching for information about what you perceive as a lack of sufficient hair above the eyes you're probably looking at something that is completely normal. That said you need to observe other behaviours and symptoms to confirm it. If, for example your cat is scratching or over-grooming above the eyes or around the face then you have to conclude that there is some sort of parasite infestation causing irritation and therefore scratching and hair loss around the eyes.
But without more; without any further signs or symptoms or indications and provided the cat is behaving normally and eating well while defecating and urinating normally, then I think you can conclude that a thin coat of hair above the eyes is perfectly normal.