Diagnosing<unk>  is difficult. A diagnosis is usually made when visual performance is poor but it is not possible to explain this from an eye examination. Before<unk>  was widely known among professionals, some would conclude that the patient was faking their problems or had for some reason engaged in self-deception. However, there are now testing techniques that do not depend on the patient's words and actions, such as fMRI scanning, or the use of electrodes to detect responses to stimuli in both the retina and the brain. These can be used to verify that the problem is indeed due to a malfunction of the visual cortex and/or the posterior visual pathway.
Cortical visual impairment
Visual pathway lesions
Cortical blindness
Dissociated sensory loss
Somatosensory disorder
Optic nerve hypoplasia
Sensory processing disorder
Congenital mirror movement disorder