Mammals have eyes similar to humas and many other animals like octopuses have a lens in the eye. So do they have such eye defects? If yes, how do they overcome it? Do they feel selection pressure against them in such cases?
do they have such eye defects?
Yes, eye defect is not specific to humans of course. Cases of eye defect are very common in animals. It is most often witnessed in domestic animals and they are the ones we observe the most (see The physiology of domestic animals)
Eye defects have typically been observed in tree shrews, monkeys (incl. macaques), cats, dogs, horses, rats, elephant and a Cape buffalo.
You should have a look at the wikipedia article Myopia in animals
howw do they overcome it?
They don't wear glasses obviously!
Humans uses the sense of vision a lot. Many animals uses smell (and taste), hearing or touch much more than humans do. For such non-visual animal, having a slight eye defect is not too big of a deal.
Do they feel selection pressure against them in such cases?
That is a bit of an awkward question. Nobody can feel a selection pressure on themselves. A selection pressure is a fitness differential associated with genotypes. A selection pressure is therefore defined at the population level. There is no such thing as a fitness pressure against a single individual.
Let me rephrase this last question to something that makes more sense. I am not sure I will address the specific question that was of interest to you though.
Are non-humans animals that have an eye defect aware that they have an eye defect?
It is unlikely that any animal would have the cognitive abilities to notice that they see more poorly than another animal of the same species. Doing so, would at least require having the ToM and only few species do.