@Amnayounas15:
Just keep eating bananas and whatever extra you are eating. You have to gain 6 or 7 pounds or about 3 kg to be in the normal BMI range. I am no expert but 3 Kgs shouldn't be an issue, particularly for a girl.
As for your eye sight, go to your eye doctor and take that test in which the doctor makes you read letters from a board. Depending on which row you can read on that chart, your doctor can tell you your visual acuity. If it falls bellow the following standard, you are not eligible. Or better yet, just take this chart to him and ask him whether your eyesight falls short of the selection criterion.
Better eye Worse eye
Distant vision without glasses 6/12 6/19
Corrected with glasses . 6/6 6/9
Near vision with or without glasses 0.6 0.6
(The distant vision without glasses is temporarily relaxed to 6/60)
Just to give you an idea. Don't come to conclusions from this image :P
It is not possible to judge your eyesight from your prescription number because that number depends on eyes' other issues as well. Though I think your eyesight too shouldn't be an issue because 6/60 with glasses is considered legally blind xP So 6/60 is an extremely poor eyesight. That
first letter is HUMONGOUS; so long as you get that right without your glasses on, you're in
)