Visual system homeobox 1 is a protein that in humans is encoded by the VSX1 gene.

The protein encoded by this gene contains a paired-like homeodomain and binds to the core of the locus control region of the red/green visual pigment gene cluster. The encoded protein may regulate expression of the cone opsin genes early in development. Mutations in this gene can cause posterior polymorphous corneal dystrophy and keratoconus. Alternatively spliced transcript variants encoding different isoforms have been described. [provided by RefSeq].
Function: Binds to the 37-bp core of the locus control region (LCR) of the red/green visual pigment gene cluster. May regulate the activity of the LCR and the cone opsin genes at earlier stages of development.