Why Did Vriska Make Terezi Blind?

Why Did Vriska Make Terezi Blind? How did Terezi go blind? Vriska mind controled Tavros, making him use his psychic powers to control Terezi’s unhatched lusus into telling Terezi to go outside and look into the Alternian sun which then blinded her. How did Terezi go blind? She used Tavros’s ability to commune with animals