This may help a little:
Symptoms: Cloudy cornea, opaque lens, pop eye, swelling, blindness.
Cloudy cornea can result from a bacterial invasion. Antibiotics may help.
Opaqueness can result from poor nutrition or a metacercaria invasion (grubs). Try foods with added vitamins and changing the diet to include variety.
Pop eye (exophtalmia) can result from rough handling, gas embolism, tumors, bacterial infection, or vitamin A deficiency. Gas bubble or bacterial infection can be treated successfully with penicillin or amoxicillin.
Blindness can be caused by poor nutrition or excessive light. Lowering the light level and a change of diet to include lots of variety may help prevent it.