The Neuroscientific Context
In the video, Oliver Sacks pointed out how his patients were labelled insane while in fact, they were truly sane, lucid people. The hallucination experience creates a sense of contradiction because they mostly occur in the elderly with impaired visual ability. In a way, it can be called 'the blind who was seeing things'. Oliver Sacks pointed out that the patients were not insane or suffering from Alzheimer’s disease, as many had believed, but rather, suffer from a medical condition known as Charles Bonnet Syndrome.

Charles Bonnet Syndrome is a condition that causes prolonged and often non-sensical visual hallucinations in patients who are visually impaired but are psychology healthy (Manford & Andermann, 1998) . The syndrome is named for Charles Bonnet, the Swiss philosopher who first described it, and is characterized by complex visual hallucinations, mainly in forms of animals and humans, in vivid situation and exotic colours but rarely disturbing their daily life (Manford & Andermann, 1998). This syndrome is mostly found in the elderly, and rarely on youth (Teunisse et al. 1996). Teunisse et al. (1996) stated that neuroleptic medication to treat this syndrome is working poorly. The apparent rarity of this syndrome is understandable, due to the fear of being labelled as ‘insane’ upon reporting symptoms. In fact, upon the admission of Charles Bonnet Syndrome under hallucinations in Diagnostic and Statistical Manual of mental disorders, it is found that this syndrome accumulated across elderly with visual impairment. Another interesting factor is that this syndrome occurred mostly in patients with higher education levels and professions hence resulting in the high levels of imagination.

Psychophysiological Features

The Charles Bonnet syndrome's typical defining symptom is hallucination that occurred as often as twice daily to twice annually. Teunisse et al (1996) found that the nature of the hallucinations might change over time, and in the content perceived. The most popular images were those of animals and humans, though some inanimate objects and complete scene also may appear. These hallucinations generally do not have any emotional impairment on the patients, though some may leave fear or distress.

Interesting enough, most of the patients recognized the hallucinations immediately when they saw it, thus stopping themselves from reporting absurd imageries and hence embarrassment. Only a minority of the patients have difficulty in differentiating the hallucinations from reality as it fits perfectly into their present context until they are usually corrected by people around them (Teunisse et al 1996). The majority of the patients however, established that the hallucinations held no personal relevance or importance and there was no reported case of patients successfully controlling the nature of their hallucinations.
Upon close observation of the physiological aspect of the patients, the Charles Bonnet Syndrome includes hallucination, visual sensory deficiency and conserved cognitive prominence (Chaudhuri, 2000). Neurological examinations on the patients usually directed at the occipital lobe, geniculostriate pathway and Visual Evoke Potential (VEP) as suggested by Menon et al (2003). This syndrome is usually associated with vision pathology problems such as cataract, glaucoma and aged-related macular degeneration. Hallucination itself is understood as the result of hyperactivity of visual neurons firing. From the study done by Foerster in 1931, it is suggested that complex visual hallucination came from the stimulation of Area 18 and 19 (the visual association area) of the primary visual cortex. As hallucination is one of the main symptoms of the Charles Bonnet Syndrome, these areas are highly regarded as the source of the abnormalities and placed under the spotlight for more understanding of this syndrome. However, Menon et al (2003) noticed that laser therapy for retinal ganglion has supported the reverse, due to the fact that by silencing discharging retinal ganglion cells, hallucination ceased to continue. They pointed out that maybe the cause of The Charles Bonnet Syndrome is not limited to entopic causes, but also brain (brain stem, occipital lobes, to name a few specific areas) lesions and rapidly signalling retinal ganglion cells.
Treatment

Menon et al (2003) also included some of the theory of Pathogenesis, which includes the theory of phantom vision, sensory deprivation experiments, dream and hallucinations, theory of perceptual release, the neuromatrix theory and many other physiological and psychological factors. To treat all these aspects of Charles Bonnet Syndrome, these steps are taken:

  1. Note taking of patient’s history,
  2. Thorough Neurological and ophthalmic examination,
  3. Counselling and reassurance,
  4. Maximizing visual function,
  5. Psychological therapy
  6. Pharmacological therapy (all steps taken from Menon et al. 2003)

These treatments have reported to be successful in some patients, while failed to reduce the hallucinations in other. Thus, every patient needs to have their own tailored treatment plan in order to treat the syndrome.
Epilepsy
It is shown by Ossola et al (2010) that the epileptic mechanism such as complex visual hallucination may have association with Charles Bonnet Syndrome. One case study of a 65 years old woman has shown the common symptoms for both epilepsy and Charles Bonnet Syndrome. Although the number of the case studies do not proofed to be statistically important, but there is a possibility of a link between the CBS and Epilepsy, based on the similarities of their symptomps and effects on the central nervous system. Thus another possible factor can be taken into consideration to determine the possible causal association between Charles Bonnet Syndrome and epilepsy.