Flicker Plus Test
Flicker-Plus test was designed to measure visual sensitivity to rapid flicker at five locations in central vision (i.e., at the point of regard and 6° away from fixation in each quadrant). The addition of cone-and rod-enhanced modules for measuring cone-and rod-mediated visual sensitivity has made Rapid-Flicker the second, most clinically important, AVOT test. The measurement of rod-mediated vision does not require dark adaptation, and this makes the test very attractive. This is also ideal for use in assessing retinal function since the results are largely unaffected by small refractive errors, higher order aberrations or increased light scatter.
Preliminary studies identified rapid flicker sensitivity as an important biomarker in glaucoma, multiple sclerosis and ocular hypertension. Flicker-Plus was developed to investigate these early observations. The test measures rapid flicker thresholds at the fovea and in each of the four quadrants. A full study designed to measure how flicker thresholds vary in ‘healthy’ aging as a function of light level has been carried out. The Night Vision module allows the measurement of rod and cone sensitivities without the need for extended dark adaptation (saving half an hour per subject) and provides useful data on rod and cone losses as a function of age or in patients with diseases of the retina.
There are two types of photoreceptors in the human retina, rods and cones. Rods are responsible for vision at low light levels (scotopic vision). They do not mediate colour vision, and have a low spatial acuity. Cones are active at higher light levels (photopic vision), are capable of colour vision and are responsible for high spatial acuity. The central fovea is populated exclusively by cones. There are 3 types of cones which we will refer to as the short-wavelength sensitive cones, the middle-wavelength sensitive cones and the long-wavelength sensitive cones or S-cone, M-cones, and L-cones for short.
The light levels where both are operational are called mesopic.
The light levels where both are operational are called mesopic.
