Hello, I'm Dr Deb. Thanks for requesting me; I'll do my best to help you and Rias today.
I'm sorry for this concern for Rias.
In general, when a dog keep their eyes closed or they're squinting (especially in bright light), this denotes pain....similar to a human when our eyes hurt or are injured.
If one eye seems worse than the other, then Rias could have scratched or injured the cornea especially if he's a very active dog or plays with other canines. Even small scratches can be quite painful.
If both eyes are involved, then a condition called uveitis (inflammation of structures in the eye) may be the reason.
You can gently rinse out the eyes with sterile saline which may bring him comfort. There are other over the counter eye drops which would be acceptable to use in a dog's eyes which I'll list below. However, I typically advise that these patients be seen so that the underlying cause can be determined (if possible) and appropriate pain and other medications can be dispensed. The over the counter products simply aren't strong enough in most cases to effectively deal with the problem. In addition, eye issues are ones which should be addressed quickly so that things don't worsen...which is often possible where eyes are concerned.
The Systane products listed below can be used in dogs, but the ones with vasoconstrictors, such as naphazoline should be avoided. These products are labeled as "taking the red out" or for "red eye".
Tears Naturale Nighttime
Systane Ultra lubricant sterile eye drops
Advanced Eye Relief Nighttime
Akwa Tears ointment
If Rias isn't vomiting nor currently taking any steroids or nsaid drugs, then Aspirin can be given at a dose of 10 mgs per pound of body weight which could help with pain. For example, the dose for a 70 lb dog would be 2, full strength, 325 mg tablets at one time, with food to avoid stomach upset.
I would also prevent him from rubbing his eyes if he's doing so. He may need to wear a cone although I know he won't thank me for suggesting it.
If the symptomatic options as listed above aren't helpful, then a vet visit may be prudent.
I hope this helps. Deb