CD4 and Nystagmus: The results of additional models, including covariates such as nadir CD4+ T cell counts (replacing current CD4+ T cell count), peak CD8+ T cell counts (replacing current CD8+ T cell count) and ever using HAART (replacing current HAART use) did not differ significantly from the original models for head thrust, Romberg ECF or gaze-evoked nystagmus (data not shown).