Dear student,

I hope you are doing well, about your question if u have some eye problem and u want to get it operated than u can do so. But after getting it operated if u still suffer some losses u may not be eligible to apply for NDA.

Now, NDA makes sure they check out all the data of a person eye like student should be able to read a distant vision chart 6/6 in better eye and 6/9 in worse eye with glasses n without glasses.

if a student suffers from Myopia, student should not be more than 2.5 D and in case of  hypermetropia it should not be more than 3.5 D including Astigmatism. You must also possess a good binocular vision.

Hope this helps!!