Abstract: A method of reducing the impact of a reading deficiency caused by a slow transient response comprises the steps of inserting a light diffuser in a reader's light path to attenuate the high spatial frequency information mediated by the cone receptors of the eye(s) of the reader, and inserting a chromatic filter which limits stimulation to the red and/or green cone receptors relative to stimulation of the blue cone receptors in the eye(s) of the reader whereby the magnitude of the cone mediated sustained response of the reader is reduced towards a more normal balance relative to the impaired transient response of the reader. An apparatus for reducing the impact of a reading deficiency caused by a too slow transient response of a reader comprises a light diffuser and a chromatic filter to limit the red and/or green mediated sustained transmission relative to the blue cone mediated transient transmission, the diffuser and filter being locatable in the reader's light path.