1. Red eyes 
Could mean an eye allergy or an infection . *The treatment for both is different .Consult your doctor , Do not self medicate *
2. Excessive blinking or rubbing of eyes 
This might be simply because the child is sleepy or anxious but it 
Could again be due to allergy or sometimes if the child has hidden refractive error ( spectacle power )and is not able to see well .
3. Cross eyes ( squint ) 
Might be due to small imbalances in development of the eye muscles but it could also be due to more serious issues like refractive error or a growth inside or behind the eye ball
4. Child goes too close to television or books while reading 
Most often the parents scold the child to not go close to TV , however the fact that the child is going close could be because she/ he is not able to view from normal distance.
5. Watering of eyes
This can be due to various reasons like hidden refractive error , allergies of the eye or nose 
And sometimes in very small babies , it could be a blocked naso lacrimal duct , which is a small passage connecting the eye to the nose and enabling proper tear circulation
6. If you see small painful boil on lid it’s a stye . If you see dandruff like flakes it’s blepharitis* and is a chronic lid infection leading to irritation , red eyes , and falling of eye lashes, May be associated with dandruff of scalp or uncorrected refractive error
7. Unusually large or small eyes
Or very obvious difference in sizes of both eyes 
These could be birth defects sometimes with less vision or no vision in the affected eye
8. Injury to eye
It could be with sharp object like pencil or blunt like a tennis ball 
In both types it’s better to visit the doctor and ensure the integrity of vision and eye tissues
9. Use of mobile or tab or computer in children
A child less than 2 years is ideally not supposed to be exposed to mobile waves except an occasionally video call. Even beyond , discourage prolonged and unnecessary use of** gadgets in kids as it’s harmful for not just eyes but also to the ears , brain and leads to deranged social and cognitive development of kids
10. Child is making silly mistakes in school and not able to cope up with studies 
This is many times mistaken for lack of intelligence only to be discovered that it’s due to poor eyesight most often correctable by glasses