The Frequency-Doubling Illusion is an apparent doubling of spatial frequency when a sinusoidal grating is modulated rapidly in temporal counterphase. Recently, it has been proposed that the illusion arises from a spatially nonlinear ganglion cell class. The presence of this illusion therefore indicates abnormalities in the retina such as glaucoma

Glaucoma

Glaucoma is an eye disorder in which the optic nerve suffers damage, permanently damaging vision in the affected eye and progressing to complete blindness if untreated. It is often, but not always, associated with increased pressure of the fluid in the eye...

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A more recent study's results argue against the hypothesis that spatially nonlinear retinal ganglion cells are the physiological substrate of the frequency-doubling illusion. A cortical loss of temporal phase discrimination may be the principal cause of the illusion, whereas spatial phase information (i.e., grating position) is retained.

Sensitivity to the spatial-frequency-doubling illusion was also positively correlated with reading lag and coherent motion. The results provide good support for a magno deficit in dyslexia

Dyslexia

Dyslexia is a very broad term defining a learning disability that impairs a person's fluency or comprehension accuracy in being able to read, and which can manifest itself as a difficulty with phonological awareness, phonological decoding, orthographic coding, auditory short-term memory, or rapid...

that has its origins at a retinal level with impairment in—at least partially—M(y)-cell activity.