He may have a problem entirely unrelated to diabetes. Eye pain, swelling, and redness needs very, very prompt attention from an eye doctor.
To add to peekawho, make an appointment with an Opthamologist, not an Optometrist. The former deals with the anatomy, functions, pathology, and treatment of the eye.
It can be hard to get immediately in to see an opthalmologist, which is why I simply said eye doctor. If the poster can get in immediately, an optometrist can also quickly discern if there is an eye-related emergency going on, and can get you referred very quickly to an opthalmologist, if need be.
"It can be hard to get immediately in to see an opthalmologist"
Lest not assume. Not in my area, not with my HMO. I can see an Opthamologist as easily and as quickly as an Optometrist. If Opthamologist' in his father's area are referral only, a visit to the emergency room would expedite matters, but then, that would depend on the area and/or country.