I have a 19 year old with cataracts in both eyes. He's had them for a few years and it doesn't seem to make any difference to him. He moves about his viv comfortably, finds the water when he needs to drink and eats reliably.
The vet told me there was nothing he could do, but as long as he was behaving and eating normally, that I shouldn't worry unless the eyes changed radically in appearance (e.g. started to bulge or appear swollen).
Corns can adapt to lost eyesight and hopefully you'll find that yours has no particular problem in coping. Their sense of smell(/taste) and heat sensing abilities seem to serve them very well in this situation.
Sometimes cataracts have been linked to the use of UV light (which isn't vital for a Corn), but this is just based on anecdotal evidence at present.
How old is your fella?