A cloudy eye (haze) in a Fire Salamander can be caused by shedding (dullness that occurs right before the old skin is cast off) / Hygiene issues in the enclosure can cause mucus buildup or irritation / Bacterial or fungal infections (can appear as a white or gray film) or injury (scratches on the cornea from sharp decor)
Check if the salamander sheds within 24 hours. If the haze remains, clean the enclosure. Do you notice any other symptoms, like lethargy or loss of apetite?