I suggest that you see the vet for a fecal exam to rule out parasites. If this is negative, your cat may need antibiotics to treat any eye infections that are present.
The vet might also want to stain the eye to look for a corneal scratch that might be the culprit.
Let me know if you still have questions.
That is a rare diagnosis and you are lucky that your vet caught it.
I am sorry that you are going through this.
You might want to look into www.carecredit.com if finances are troublesome for you. They offer financing for large and small vet bills with easy terms.