Abstract: Apparatus for testing dark adaptation comprises a test panel. Four test stimuli, comprising arrays of light emitting diodes, are arranged on the test panel around a fixation light emitting diode. Translucent covers are mounted over the arrays of light emitting diodes. Four switches to enable a subject to input the identity of a visible test stimulus are provided, each switch is operated by a button formed by a respective cover of the test stimuli. A test stimulus is randomly selected and switched on at a predetermined level of luminance. On a correct identification, another test stimulus is selected and switched on at a reduced level of luminance. The times from the commencement of the test until the various correct identifications are recorded, as are the corresponding level of luminance of the test stimuli.