Most likely your frog was part of a laboratory study or serious injury/disease. Clawed frogs are the model lab subject. In the world of Xenopus, vision is of little use. The eyes are designed to detect prey outside the water - birds, for example. Because the frog is in captivity, there are no predators flying overhead the aquarium - at least I hope notand vision is not needed.
Xenopus has three methods of sensory perception: wave detection using lateral line organs, hearing and chemoreception (smell).