I did once have a betta with this problem, and interestingly he was the same colour as yours.
Your betta (and mine) is a dragonscale, and this type has extra thick scaling which is prone to growing over their eyes. They can still find their way around the tank using their other senses, but I always made sure that when I cleaned the tank, if I moved any decor I put it back in exactly the same place, and I always put his food in exactly the same place. I didn't do this, but other members have said that they tapped gently on the tank just before feeding and the betta quickly learned that the tapping meant food and swam to the feeding place ready.
This is my betta. He was completely bind in one eye with limited sight in the other.
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And when I first got him (yes, I did have fake plants back then
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