In two articles looking at blur sensitivity, Professor Edward Mallen defined blur sensitivity, blur adaptation and blur discrimination1 and then looked at how blur sensitivity can influence aspects of the refraction undertaken during the routine eye examination.2 These two articles were then used as the source material for an interactive CPD exercise.
Blur sensitivity is a measure of the ability of the visual system to detect blur. In research experiments, blur sensitivity can be assessed subjectively using relatively simple equipment, and can be expressed as a dioptric threshold. Such experiments are generally conducted monocularly and under cycloplegia and with a standardised artificial pupil.
Blur discrimination is the ability to determine whether one target is blurred by a different amount in comparison to a reference target.
Blur adaptation describes the ability of the visual system to improve its character recognition abilities following exposure to blur, but without a change in refractive error.
A significant part of any routine eye test is the measurement of the refractive error of the eye. While this may be undertaken objectively, by retinoscopy or autorefraction, for most patients the final refractive correction is established subjectively and may differ from the objective result as it better reflects the preferred viewing of the patient. However, the very subjective nature of the testing is a potential source of variation between patients.
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