I've got a humanoid race living in a extremely bright and hot desert. Would there be a plausible or realistic reason for them to develop without eyesight, due to the harsh rays of their sun? Or, instead of eyes, developing some other form of vision (echolocation, some sort of extra sense, etc)?
Vision has a lot of advantages as a sense. It's very long-ranged, and provides a lot of information. Eyes evolved several times in Earth's history, and take lots of different forms. Human eyes are much like those of other primates, which are similar to those of other mammals.
It seems likely that if life evolved naturally in your setting, some kind of vision would exist, although it might be very different from ours.
No. Vision is by far the most important sense for a humanoid species. It would, perhaps, be plausible for a non-humanoid race to evolve a stronger reliance on other senses to survive in the desert.
Check out other desert animals - they also have eyesight!
In general, eyesight itself is quite vital, so you may not expect for it completely missing, especially taking into account that albedo is not so extreme in the brown-yellow sand. (unlike the poles, where everything's white, so "snowblind" state is a general phenomena)
Reduced eyesight is perfectly possible, though I'd separate it more - our eyes are able to detect colors and light with two different types of cells(?), and having less of the latter sounds realistic for me.
I'm not an expert, so I'm not sure, how would that change the ability to see, so it may or may not be a better eyesight with less light receptors, but it's a topic for another (likely rather biology-related) question.
I would be of the opinion that for land animals to have not have evolved eyes, the habitable land area on your planet must consist solely of this desert. If they live in an extremely bright and hot desert, would it make more sense for these creatures to be nocturnal? Or perhaps if it is too cold at night (as with Earth deserts), they are active during twilight hours. If so, eyes would most likely have evolved.
With that in mind, what is the evolutionary advantage pushing these creatures to be active during the day, and thus having no use for eyes? Are they protected from nocturnal predators when sleeping? Just something to consider.
If your humanoids are nocturnal and live on a moonless planet orbiting a star on the galactic rim then they’ll be living in a nearly pitch black environment, in which case lacking eyesight makes perfect sense.
Maybe daylight is too hot to survive or the planet's magnetosphere is too weak to adequately protect them from ionizing particles?
Maybe you could go with them evolving underground(Due to extreme temperatures or something similar). Then as time went on they developed an ability(Technology? depends on setting and their tech level) to go to the surface. As primarily underground creatures, they probably would not evolve eyesight (Or even loose it if they had it at some point). If days are to hot to be outside, and nights extremely dark, there would be no need for eyesight to evolve.
i think it still depend on your race and its evolution. if your entire world is desert like this, then it possible for your species to skip the evolution of eye completely (thus avoid mirage), to develop echolocation or sense of smell, hearing, or heat (like the rattlesnake).
however, if your race came from somewhere else, or had evolved eyes already, then it s more plausible for them to add some features like an outer layer which act like sunglass, or switch their activity to nocturnal or crepuscular (at twilight) instead of devolve your eyes then evolve something else.