Method and apparatus for measuring a property of an eye of a subject

Abstract

According to a first aspect of the present invention, there is provided a method of measuring a property of an eye of a subject using an apparatus which is: arranged to provide a bleaching light, a background light ostensibly invisible to rods (e.g. substantially red, and/or having or being a wavelength greater than 580 nm) and a target light ostensibly visible to rods (e.g. substantially green, and/or having or being a wavelength less than 580 nm and greater than 400 nm, e.g. around 514 nm+/−50 nm), the background light and/or target light (together) being suitable for rod-dominated stimulation, the background light and target light being superimposable upon one another, and the target light being presentable to the subject such that the target light is incident on a parafoveal region of the subject's retina; the method comprising: a) stimulating the subject's retina with a low level bleach using the bleaching light; b) after the bleach has been undertaken, modulating a target light at an initial luminance at which modulation of the target light is not perceivable by the subject, whilst a background light remains substantially constant; c) increasing the luminance of the modulated target light; d) receiving an input from the subject when modulation of the target light is perceivable by the subject, thus indicating a rod-related threshold; e) after said input, decreasing the luminance of the modulated target light; and f) repeating parts c) to e) of the method to determine a series of rod-related thresholds over a period of time.