You can never be to careful when it comes to the eyes. If a pet is showing problems with the eyes, even if it is as much as an itching or redness you should worry and treat it with precaution.
#1-If you notice that your pup avoids bright lights, squittens or blinks excessively you should take him in for an eye examination. Most of the eye injuries occur when an object enters or becomes embedded in the eye, but also abnormal growth of the eyelashes, scratching or pawing the cornea can lead to eye injuries as well.
#2-If the eye is out of the socket it needs to be treated urgently in order to save your dogs eye sight. Until professional help arrives you can soak a damp in warm salty water and cover the eye with it.
#3-If your dog is blinking excessively and avoids bright lights there is likely something stuck in his eye. You can try and remove it by lifting the upper and the lower eyelid to see what is causing his blinking. Once you notice it use a damp cotton swab to ease it out or if that does not work try to flush it out with tepid water. At worst if you do not succeed at removing it, take your pup to the vet as soon as possible.
#4-The case of a red eye usually means it has bean scratched excessively. Check if there is anything stuck in your pups eye and if not use a clean cloth and bandage it to the eye to prevent any additional injuries and take him to the vet.
#5-When you notice a bruised eyelid, pressing a cold compress in the eye will do to help with the swelling. In case you are concerned that your dog might have been exposed to chemicals than his eyes may have burn damage. Flash immediately with fresh water and bandage the eye before you take him to the vet.
#6-If you see watery or yellow, green watery charge flush the eye with tepid water.