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---------------------------------------------------------------------------- Letters to the Editor - July 1997 - Archives of Neurology ---------------------------------------------------------------------------- Visual Loss as a Causative Factor in Visual Hallucinations Associated With Parkinson's Disease ---------------------------------------------------------------------------- The study by Sanchez-Ramos et al [1] delineates a number of factors that predict the development of hallucinations in patients with Parkinson's disease. Complex visual hallucinations occurred in more than 55 (25%) of the study population of 214 consecutive patients with PD and they were strongly associated with age, dementia, disease duration, depression, and sleep disorders. The absence of detailed ophthalmological evaluation in these patients precluded an accurate estimate of visual loss that is an important cause of visual hallucinations. Complex hallucinations have been reported in 22 (21%) of 104 consecutive patients with retinal and neural afferent visual pathway lesions causing trivial to profound visual loss. [2] Cogan [3] has conjectured that such hallucinations stem from ongoing cerebral activity of the visual system and are released by removal of normal visual input. Along with neurological disorders, toxic and metabolic abnormalities, psychiatric disorders, and miscellaneous conditions, including sleep disturbances and sensory deprivation, dysfunction of the ocular and central visual pathways with resultant release visual phenomena constitutes a major cause of hallucinations. Many causes of visual loss are age related. Senile macular degeneration affects nearly 30% of people older than 75 years [4] and the prevalence of cataract between the ages of 65 and 74 years is 18% of the US population. [5] In the study by Sanchez-Ramos et al [1] the mean age of patients hallucinating was 70 years, and it is highly likely that a portion of this cohort had age-related visual loss sufficient to cause release hallucinations. The authors state that often the hallucinations associated with PD suggested the Charles Bonnet syndrome that was originally characterized in 1769 by visual hallucinations in sane elderly people. [6] More recently, most patients with Charles Bonnet syndrome have been found to have visual loss, [7] and Bonnet's [8] original patient underwent primitive cataract surgery. Clearly, visual loss was a cause of visual hallucinations in Bonnet's era and should be sought in the present day. Consonant with the supposition that some of this study's patients with PD have hallucinations attributed to visual loss, there are diagnostic and therapeutic implications. Thorough ophthalmological evaluations, including visual acuity and perimetry, should be performed in all patients with a history of hallucinations, and in the case of a hallucinating patient with PD and visual loss, there may be need for ophthalmological therapy, eg, cataract extraction, rather than "reduction or rearrangement of medication" for PD or addition of clozapine. [1] There are undoubtedly multiple factors in the genesis of hallucinations in PD, but visual loss is a well-documented cause and is potentially reversible with treatment. Frederick E. Lepore, MD Department of Neurology 1 Robert Wood Johnson Pl UMDNJ/Robert Wood Johnson Medical School New Brunswick, NJ 08903 References 1. Sanchez-Ramos JR, Ortoll R, Paulson GW. Visual hallucinations associated with Parkinson disease. Arch Neurol. 1996;53:1265-1268. 2. Lepore FE. Spontaneous visual phenomena with visual loss: 104 patients with lesions of retinal and neural afferent pathways. Neurology. 1990;40:444-447. 3. Cogan DG. Visual hallucinations as release phenomena: Albrecht V Graefe. Arch Klin Exp Ophthalmol. 1973;188:139-150. 4. Klein BE, Klein R. Cataracts and macular degeneration in older Americans. Arch Ophthalmol. 1982;100:571-573. 5. Kahn HA, Leibowitz HM, Ganley JP, et al. The Framingham Eye Study, I: outline and major prevalence findings. Am J Epidemiol. 1977;106:17-32. 6. Berrios GE, Brook P. The Charles Bonnet syndrome and the problem of visual perceptual disorders in the elderly. Age Ageing. 1982;11:17-23. 7. Teunisse RJ, Cruysberg JR, Hoefnagles WH, Verbeek AL, Zitman FG. Visual hallucinations in psychologically normal people: Charles Bonnet's syndrome. Lancet. 1996;347:794-797. 8. Bonnet C. Essai Analytique Sur Les Facultes de L'Ame. 2nd ed. Copenhagen, Denmark: Philbert; 1769. (Arch Neurol. 1997;54:799) Contents copyright 1997 American Medical Association. All rights reserved. <http://www.ama-assn.org/sci-pubs/journals/most/recent/issues/neur/letter_1. htm> ---------------------------------------------------------------------------- ---- [log in to unmask]