Purpose: Little is known about neuronal changes during ageing in the visual system of mice which are increasingly being used as animal models for human visual disorders. Methods and results: Measuring the optomotor response to moving gratings, visual acuity of C57BL/6-mice was 0.39 cycles/degree (cyc/deg) until 12 months of age and declined to 0.27 cyc/deg (by 30%) at 26 months. In the visual water task, a cortex-dependent task based on visual discrimination learning, visual acuity remained stable at 0.58 cyc/deg up to 21 months and then declined to 0.48 cyc/deg (by 19%) at 27 months. Visual cortical activity recorded by optical imaging declined by 33% between seven and 23 months of age. After monocular deprivation and daily testing of the optomotor response, visual acuity of the open eye increased by 29% in 4 to 7-month-old animals, while the increase was only 13% in 23-month-old mice. Interestingly, interindividual variability generally increased with age, so that some 23-month-old mice retained visual acuity and interocular plasticity like 4 or 7-month-old animals. Conclusions: In summary, reduced visual function was accompanied by a reduction of both visual cortical responses and interocular plasticity indicating a central nervous system component in age-related vision loss in mice.