Goldfish eye disease I cant identify

Question
QUESTION: My kids have a telescope eye goldfish.  It is the only fish in a 20 gal tank.  The tank set up is fine (filter, air, ph, ammonia, cleaning intervals, etc) and has been stable for over a year.

All of a sudden (as in it was fine at night and in the morning it was there) the fish developed what looked like a small ball of cotton in its eye. It was not clouding like a cataract, but a sphere of white material. If the eye was the size of a basketball, the sphere was the size of a tennis ball. This "thing" was INSIDE the lense (not on it - inside it) and outside of the iris.

Anyway -  I used a course of quick cure and the next day it was gone.


I just wonder what the fish had.  I would have said it was a fungal infection, but the inside the lense of the eye part has me wondering.

Thanks


ANSWER: Yeah it would have been a fungal infection, it happens alot in eyes, im glad you can clearly care for your fish properly

---------- FOLLOW-UP ----------

QUESTION: Thanks for the answer. Is there anything in particular that can cause it?

Answer
Yeah.
Spores of fungi are always present in aquariums and healthy fish are usually unaffected by them. Unhealthy fish are more susceptible, however mouth funguscan be a problem with bottom feeders in an aquarium with a crushed gravel substrate. Body fungus can appear if the fish are rougly handled by abrasive handling in the net or by fighting other fish. If the skins protective layer is damaged or removed, fungus spores will go straight to work. careful handling can prevent this, as can the use of round gravel as a substrate.
Problems accur in the best kept tanks. If your fish become ill, do not panis, but try to solve the problem as quickly as possible. Tip: wear plastic or medical gloves when treating the fish so that you do not damage your skin if you spill chemicals or treatments: the life of some chemicals can be very short after opening