Diseases that damage the retina, the optic nerve, or the blood vessels that feed them often cause no pain at all. The primary symptom is deteriorating vision, which is usually stoppable but not reversible. That's why it's vital to get your eyes checked regularly. One possible symptom of internal eye damage is floaters, tiny fragments in the liquid inside the eye. You see tiny bubbles or dark spots slowly falling through your line of vision. Everyone has a few floaters - you should only worry if you notice a sudden increase in them.

Almost all eye infections accompany disease in some other part of the body, even if it's just a cold. Some but not all of these diseases have clear symptoms. Be on the lookout for eye pain or visual symptoms if you have any of the diseases listed in the 'Causes' section of this article.

Serious complications of eye infection include damage to the retina and the formation of scars and ulcers in the cornea that can obstruct vision. Some infections, like syphilis, can also provoke glaucoma. Moreover, eye problems are often the only visible symptom of wider infections. Chlamydia, for example, often causes no genital symptoms, but can cause infertility and heart damage if left untreated..