Melonoma Is Iris Melonoma The Only Cause For Freckles Developing In A Feline's Eye Iris?

Is iris melonoma the only cause for freckles developing in a feline's eye iris? - melonoma

My cat of 12 years, is still very playful for his age, but 3 months before the right eye has begun to change color. They (a black coat with yellow eyes) More recently, the right eye is "Iris" has developed brown spots / freckles and appear every day look worse. Is it really a melanoma cancer, or it could be something that antibiotics can cure? It seems very sudden. I am very worried. What can cause these symptoms?