Dear XXXX,
There are many possibilities. Your pouch could have a foreign body in his eye, his eye could have suffered trauma such as a cat scratching his eye, he could have an infection caused by bacteria, he could have an ulcer on his cornea caused by trauma, infection. These are the most common causes.
You could wait a short time such as a day to see if the problem clears. It may just be a hair that is in his eye. If it is not better in a short time, you can take him to your vet who will give him a complete opthalmic exam. Your vet can place drops in his eye that will numb it to make the exam easier.
If you found my answer helpful, please press accept. Feel free to contact me if you need more clarification.
Dr. KM
Veterinarian
Veterinarian with many years of large and small experience in medicine, surgery, dental, behavior.