tokens: Three major criteria , saccade amplitude , saccade velocity , and presence of gaze - evoked nystagmus , permitted the correct assignment of 90 % of the SCA1 , 90 % of the SCA2 , and 93 % of the patients with SCA3 to their genetically confirmed patient group and , therefore , may help orient diagnoses of SCA1 , SCA2 , and SCA3 at early clinical stages of the diseases . .