Monitoring glaucoma patients represents a significant burden on clinical services, with an estimated one million visits annually in the UK alone. Visual field (VF) tests are routinely used for detecting worsening of vision. We aimed to estimate VF loss during patient's predicted lifetime by examining around 250,000 VF tests from three different glaucoma clinics in England. Patients were excluded if they had too few VFs or insufficient follow-up (less than 3 years). Levels of VF loss were summarised using the Mean Deviation (MD) index from each test. MD at diagnosis and MD loss during predicted remaining lifetime, using a linear rate of MD deterioration (dB/year) and residual life expectancy tables, were calculated and plotted on motion graphs. Most patients followed in clinics have stable disease. Four percent (95% confidence interval: 3 to 5%) of patients were predicted to be at risk of statutory blindness in their lifetime. Likelihood of a patient suffering serious visual impairment in their lifetime is linked to level of VF loss at presentation. These findings from retrospective analysis of ‘big data’ could help inform planning of follow-up in glaucoma and also illuminate the importance of detecting the disease in primary care.