Your Tru Glos are probably just suffering from scratching of the ends and/or sides, or a condition called "crazing" which is usually cause by exposure to a solvent. A going over with a quality polish for acrylic plastics should restore them, remove the rods and clean them thoroughly with the polish.
ORIGINAL: TEmbry15
i could be wrong but im pretty sure there is no liquid in truglo sights. fiber optics are just that...little tiny fibers. not sure if they go dull or not but i do know you can replace just the fiber part extremely easy.
The rods used for "fiber optic" gun sights are usually just high clarity acrylic plastic, not true fiber optic fibers which are made from extremely pure glass and unlikely to be sold for $15-25 at Wal-Mart. One of the things I don't like about Tru Glo is that their rods break very easily, a problem I haven't had so far with the Hi Viz sights that Maytom mentioned. My turkey gun has Hi Viz rifle type sights rather than a single rod on the muzzle end, it's deadly accurate.