CD4 and cytomegalovirus retinitis: CD4+ T lymphocyte counts have been used to predict the onset of several ocular infections in HIV-positive persons (Douek et al., 2009); for example, studies have shown that patients with HIV infection with CD4+ T lymphocyte counts below 100 cells/μL often have retinal or conjunctival microangiopathy as well as CMV retinitis (Ei et al., 2019).