Patients that once had excellent vision sometimes report seeing crystal clear images of nature, faces and other objects. Most of these patients have experienced severe loss of vision in both eye; usually from a disease such as macular degeneration. They have lost the ability to read and many are worse than legally blind.
What is happening? These visual hallucinations are usually a result of a type of sensory deprivation and was described many years ago as the Charles Bonnet Syndrome (CBS). It occurs in patients that no longer able to see well. The brain, deprived of visual stimuli, knows that it should “see” better and may “create” these images.
Are these people crazy? Usually not, but they are usually elderly, very coherent and scared. They are quite aware that their vision is poor and that they have long lost the ability to see “clearly.” They are worried that they are becoming psychotic and the family is concerned about dementia. It is reassuring to everyone once it is explained that CBS may be a cause of the phenomenon.
When I suspect CBS, I usually compare “phantom pain” to my so-called “phantom vision.” I usually recommend to the family, that if there is other, non-visual, suspicious behaviors, the PCP should be alerted.
Randall V. Wong, M.D.
Ophthalmologist, Retinal Specialist