PPT1 and infantile neuronal ceroid lipofuscinosis: Since loss of vision occurs in patients with INCL, and since the older Cln1−/− mice exhibited impaired performance on the two types of MWM cued trials, we evaluated an independent, 7-month old cohort of Cln1−/− and WT control mice on the virtual optomotor system (VOS) to determine visual (grating) acuity thresholds.