[header] How to diagnose eye problems in pugs [title] Spot the signs of corneal ulcers. [step] The cornea is the transparent layer on the front part of the eye. In order to see, light needs to pass through it to reach the lens and the retina. 
If a dog has corneal ulcers, which is like a divot in the cornea, they will affect the ability of light to pass through the cornea, inhibiting the vision of the dog. [substeps] Signs include your pug holding its eye closed or squinting a lot.