The "Eyes" Have It

May 9, 2018

A simple diagnostic test for Lewy body dementia?

Assessment of color vision impairment (CVI) may be a cost-effective, easy, and relatively reliable way of diagnostically distinguishing dementia with Lewy bodies (DLB) from Alzheimer disease (AD), according to results from a retrospective study conducted at the Cleveland Clinic’s Lou Ruvo Center for Brain Health in Cleveland, Ohio.1

DLB is frequently misdiagnosed as AD and, until fairly recently, was generally only distinguished from AD on autopsy.  A team of Cleveland Clinic researchers, however, discovered that CVI in persons without a prior history of color blindness was common among their study subjects with DLB. Indeed, 78% of their study cohort with DLB tested positive for newly detected CVI compared with 15% of their subjects with AD.

The researchers noted that CVI has been associated with both Parkinson disease and DLB in association with rapid eye movement sleep disorder (RBD).2,3 Theirs is the first study, however, to explore the prevalence and characteristics of CVI in a broader sample of patients with dementia, with the  aim of improving the detection and diagnosis of DLB.

The study included 52 patients with either a diagnosis of probable DLB or AD or mild cognitive impairment (MCI) suspected of being prodromal AD or DLB. Prodromal AD was defined as amnestic MCI and biomarker evidence of pathological changes consistent with AD. Prodromal DLB was defined MCI with suggestive features of Lewy body pathology, including possible RBD and/or Parkinsonism. Median patient age was 76 years, and only patients who underwent an online Farnsworth 15-hue color vision screening test at the Cleveland Clinic were included in the study.

Patients were divided into 4 groups: prodromal AD (n = 5), AD (n = 15), prodromal DLB (n= 8), and DLB (n = 24).  Patients with a history of CVI (n=4; 1 each in the prodromal AD and DLB groups and 2 in the AD group) were distinguished from patients with newly detected CVI.

Newly detected CVI was identified in 1 (25%) of 4 patients with prodromal AD, 2 (15%) of 13 patients with AD, 3 (38%) of 8 patients with prodromal DLB, and 18 (78%) of 23 patients with DLB. The difference was statistically significant (P < .001) and appeared to suggest that new-onset CVI is among the distinguishing diagnostic features of DLB. Although larger, prospective studies need to be conducted, these findings are promising in presenting a potentially highly cost-effective and efficient way to differentiate DLB from AD early in the disease process and, thus, better ensure appropriate patient care.

References:

1. Flanigan PM, Khosravi MA, Leverenz JB, Tousi B. Color vision impairment differentiates Alzheimer dementia from dementia with Lewy bodies. J Geriatr Psychiatry Neurol. 2018;31:97-102.
2. Piro A, Tagarelli A, Nicoletti G, et al. Color vision impairment in Parkinson’s disease. J Park Dis. 2014;4:317-319.
3. Postuma RB, Gagnon J-F, Vendette M, et al. Olfaction and color vision identify impending neurodegeneration in rapid eye movement sleep behavior disorder. Ann Neurol. 2011;69:811-818.