Clinical vision measurements usually involve printed charts with an eye care professional interpreting patient responses to generate a score. Those scores determine the need for or outcome of treatment. Detecting change can be improved with strict procedures/scoring, lending itself to computerisation. This in turn allows integration with electronic medical records. Many eye tests could be computerised in this way. At Guys and St Thomas' NHS Foundation Trust, the investigators have developed and validated a computerised test of distance visual acuity, called COMPlog which is now in widespread use. The investigators now want to increase the range of tests available. There is also a need to longitudinally monitor for adverse change. Such monitoring must be developed to keep false positive and false negative change detection to a minimum. The aims of this two year linked program are to: Part A) validate an extended range of computerised vision measurement tests against their gold standard hard copy printed equivalents. Some of these tests are designed for use in children and all are meant to quantify both normal and impaired vision. Patients of all ages and visual function will therefore be recruited from St Thomas' Hospital. The specific tests we aim to validate are logMAR Letter Near Acuity, Word Near Acuity, Letter Contrast Sensitivity, Auckland Optotypes Picture Acuity, Low Contrast Letter Acuity, Stereoacuity and Vanishing Optotypes. Patients will undergo test-retest measurements with up to two of these. Part B) Iteratively develop an application for use in home monitoring of subjects at risk of treatable vision loss due to age related macular degeneration. All computerised tests in parts A and B will be performed on prototype software. Eye patients will be recruited as subjects. Patients recruited to part A will undergo tests on one day for up to an hour, subjects in part B will participate for between 1 hour and two months.