This is a follow up to a previous question where I asked how I could imply that a sentient serpentine race was originally burrowers. I'm trying to design their eyes, but I'm having trouble deciding what the limits should be. They still come from an eyeball Earth around a red dwarf star. They can be from one that's stopped flaring, although they could be from a still flaring star.
In real life, many burrowing/cave dwelling animals have a reduced sense of vision or have completely lost their eyes. For instance, the star-nosed mole is functionally blind, but has evolved highly developed senses of touch and smell. It's not efficient to spend resources on a sense that doesn't get much use. Since red dwarf stars have a very low luminosity, that would be another potential reason for a species to become less reliant on sight.
Going back to the mole comparison- there's no reason that a sapient species couldn't be blind and reliant on other senses. For instance, they might record information through a system similar to Braille or quipu (Inca knot-writing), rather than written text.