Vision testing system comprising vision testing apparatus and a processing centre remote from said vision testing apparatus, wherein: the vision testing apparatus comprises: a local display; means for obtaining data characterising the performance characteristics of said local display; means for displaying to a user at said local display, an adapted vision test that comprises an adaptation of a reference vision test; means for registering user input in response to said displayed adapted vision test; means for providing the user with the results of said displayed adapted test; and a communications interface configured for transmitting information to and receiving information from said remote processing centre; the remote processing centre comprises: a communications interface configured for receiving information from and transmitting information to said remote vision testing apparatus; means for adapting a reference vision test in accordance with display performance characterising data received from said vision testing apparatus to provide an adapted vision test for display at said local display; and means for sending adapted vision tests from said remote processing centre to said vision testing apparatus for display at said local display; wherein said reference vision test comprises a test that is optimised for display on a high quality display, and said adapted vision test for display at said local display is an adaptation of said reference test that enables said reference test to be faithfully reproduced at said local display; characterised by said adapting means being configured to calculate, based on said characterising data, the luminances of red, green and blue display primaries that are required for the faithful display of the luminance and chromaticity triplets of said reference test at said local display. the vision testing apparatus comprises: a local display; means for obtaining data characterising the performance characteristics of said local display; means for displaying to a user at said local display, an adapted vision test that comprises an adaptation of a reference vision test; means for registering user input in response to said displayed adapted vision test; means for providing the user with the results of said displayed adapted test; and a communications interface configured for transmitting information to and receiving information from said remote processing centre; a local display; means for obtaining data characterising the performance characteristics of said local display; means for displaying to a user at said local display, an adapted vision test that comprises an adaptation of a reference vision test; means for registering user input in response to said displayed adapted vision test; means for providing the user with the results of said displayed adapted test; and a communications interface configured for transmitting information to and receiving information from said remote processing centre; the remote processing centre comprises: a communications interface configured for receiving information from and transmitting information to said remote vision testing apparatus; means for adapting a reference vision test in accordance with display performance characterising data received from said vision testing apparatus to provide an adapted vision test for display at said local display; and means for sending adapted vision tests from said remote processing centre to said vision testing apparatus for display at said local display; a communications interface configured for receiving information from and transmitting information to said remote vision testing apparatus; means for adapting a reference vision test in accordance with display performance characterising data received from said vision testing apparatus to provide an adapted vision test for display at said local display; and means for sending adapted vision tests from said remote processing centre to said vision testing apparatus for display at said local display; wherein said reference vision test comprises a test that is optimised for display on a high quality display, and said adapted vision test for display at said local display is an adaptation of said reference test that enables said reference test to be faithfully reproduced at said local display; characterised by said adapting means being configured to calculate, based on said characterising data, the luminances of red, green and blue display primaries that are required for the faithful display of the luminance and chromaticity triplets of said reference test at said local display.