<s>[INST] <<SYS>> This is a medical question of type : frequency <</SYS>> How many people are affected by X-linked infantile nystagmus ? [/INST] The incidence of all forms of infantile nystagmus is estimated to be 1 in 5,000 newborns; however, the precise incidence of X-linked infantile nystagmus is unknown. </s>