It's not clear if Vader actually needed the lenses on his helmet to see properly. Given that he had to cover his burned flesh anyway, the helmet lenses offered other benefits, such as viewing different light spectrums, a heads-up display, and making him intimidating. Those alone could be enough to justify covering his eyes.
However, it's perfectly plausible that his eyes were injured by the lava, like the rest of his body.
The one source I could find to say his eyesight was damaged was a Legends continuity book, Darth Vader: A 3-D Reconstruction Log (as cited in another Sci-fi Stack Exchange answer, which provided the image below - thanks, Valorum). According to that, Vader's retinas were damaged beyond repair.
Repairing the patient's damaged retinas proved impossible. But optical filters in the mask block excess light and expand the limits of human vision by detecting infrared and ultraviolet light.
It's not clear how bad the damage was, though. We know he's not completely blind because he can see the helmet display and he can see Luke's face with his own eyes in Return of the Jedi. With those two examples, it's possible he's just short-sighted and the lenses compensate for that, like a very evil pair of glasses.