TYR and pathologic nystagmus: OCA1 is the type caused by mutations in the TYR gene and is further classified into two subtypes: OCA1A, a more severe form resulting from a complete lack of tyrosinase, leading to white hair, light skin, and light blue eyes with severe visual impairments, including nystagmus, strabismus, and photophobia, and OCA1B, a milder form, in which TYR gene mutations partially impair tyrosinase activity, allowing for minimal to moderate melanin synthesis.