What's wrong with his eye?

Hi does anyone know what's wrong with his right eye? It was red before this happened.

Hello!  I can see Muffy's third eyelid, part-covering the eye from the medial canthus (nose-side corner).  This can happen for several reasons, one of which might be damage to the nerve supplying the third eyelid (usually held fully open) and another of which may be pain.  I am interested in the neurological possibility as the temporal muscle of the face appears to be reduced in volume from this angle when compared to that of the other side, which may be connected.  This might also be caused by a lack of neurological input to the area.  Horner's syndrome (a syndrome is a typical pattern of clinical signs that occur together, in this case ptosis, meiosis and endopthalmus) should be considered;. it occurs for various different reasons.  It is hard to tell from the photo what the pupil is doing, but a vet could examine the eye properly, check the facial nerves and for eg foreign bodies, before deciding where to go from there.  Both eyes look somewhat reddened to me and although this is common in dogs of this breed, it is not normal; it could be from rubbing of the area, for example the result of chronic skin disease (eg allergy) or a response to pain.  I cannot see a prolapse of the third eyelid, but this is also possible. Whatever the cause, a vet needs to examine the eye and as it may be an emergency; please contact your emergency team to make plans.

Thank you for your very detailed reply. I really appreciate your effort. I left him in the care of my parents for a while because of my job situation. They are stubborn and not very consistent with my instructions. I found this https://www.petcoach.co/question/?id=597718 . It has a picture of a dog with same problem. It got soap in its eye. Poor shower practice?

There is an important point to be made here.  The dog in the article you sent appears to have conjunctivitis.  Your dog also appears to have conjunctivitis.  Conjunctivitis means inflammation of the eye (with a protruded third eyelid in both of these cases). HOWEVER, this doesn't tell you what's wrong with the eye. Let me give you a parallel:  I have a runny nose today.  My elderly neighbour also has a runny nose.  The two runny noses look much the same;  however, mine is caused by a cold and hers is connected to a cancer of the upper respiratory tract and she is unlikely to survive the year. The 'sameness' you see in those photos are in the symptoms.  The other dogs' vet knows that the redness started acutely (suddenly), coinciding with getting soap in the eye, so it is a reasonable assumption that soap in the eye is what caused the symptoms in that case. HOWEVER, the same symptoms could also be caused by any of the other things that I mentioned.  Some of these are extremely serious and need rapid or immediate treatment.  Red eyes are often a medical emergency and, even though getting soap in the eye may be one possibility, you still need to report this to your vet.