Good fine CPD, I grabbed another book out of the library of my club and found this, perhaps it will help.:
"Popeye is a generic term for Exophthalmos, and refers to a condition that causes the eye of the fish to abnormally bulge from its socket. Popeye can be caused from bacterial disease, abscesses and tumors, eye injuries, as well as over-aerated water. if left untreated, the eye may buge so far from its socket that it pops out, resulting in the loss of the eye. If the fish has other signs of disease, use the Fish Problems Flow Charts (sorry I can't type the charts in here =) ) to determine the cause and treat accordingly.
Symptoms:
One or both eyes protrude from the socket(s). Some fish also exhibit a lack of appetite.
Treatment:
First, eliminate the possibility of over-aeration. If you have been using high-powered powerheads that shoot streams of air into the fish tank water, your fish may be a victim of nitrogen supersaturation. The tiny air bubbles enter the fish's bloodstream and can accumulate behind the eye, causing it to protrude.
The treatment for nitrogen supersaturation, is to turn the powerhead water stream adjustment to its lowest setting. Temporarily shut the air off to the powerheads and allow the air pump to be the only source of air. Observe the popeye for a few days. If nitrogen supersaturation was the problem, the eye should begin to recede. If no improvement is noticed, or if it worsens, assume the prolbme is bacterial in nature."
The book is called
The Complete Aquarium Problem Solver: A Total Trouble-Shooting Guide for Freshwater and Marine Aquariums. By Kevin W. Boyd. Published in 1993 (so it isn't the latest out there obviously)