Eyeworld

EW NEWS & OPINION 20 December 2015 by Matt Young and Gloria D. Gamat EyeWorld Contributing Writers for monitoring progression from normal and abnormal age-relat- ed processes, such as for instance supranuclear cataract and opacities of ocular lens, to the pathological neural degeneration undoubtedly associated with MCI and AD." Other research and reaction Internationally, similar findings are being made. "Besides the cognitive impair- ment and degeneration in the brain, vision dysfunction and retina dam- age are always prevalent in patients with Alzheimer's disease," according to a report by Lixiong Gao, MD, Southwest Hospital/Southwest Eye Hospital, Third Military Medical University, Chongqing, China, in Experimental Eye Research in June 2015. Dr. Gao and colleagues found that a medication for Alzheimer's called memantine (MEM) also "rescued the loss of retinal ganglion cells (RGCs), as well as improved "Multiple forms of evidence points toward the involvement of retinal ganglion cells and their axons in the optic nerve as a basis of the visual dysfunction in AD," Dr. Coppola said. "In fact, histo- pathological lesions associated with AD—neuronal loss, beta-amyloid plaques, neurofibrillary tangles, and granulovacuolar degeneration— have been seen not only in brain structures historically thought to be involved in AD, but also within the neuroretina." That's why there has been par- ticular interest in OCT. "Taking in mind that the human eye is an embryological pro- trusion of the brain, and the nerves and axons of the RNFL is a tract of the brain, it is not surprising that OCT has been widely employed in assessing RNFL thickness in several neurological disorders," Dr. Coppola reported. "In this context, reduced retinal thickness measured with OCT may be a promising biomarker quadrant for this group) compared to controls. "OCT can be useful to detect early RNFL abnormalities in MCI patients," Dr. Coppola reported in his study. "Whether the subgroup of MCI patients with thinner RNFL have a higher annual incidence of conversion to AD remains to be determined in an appropriately designed study. This is of particular interest in view of using OCT as a paraclinical test with prognostic value. We will see RNFL thickness measurements in patients with other dementias as an aid to diagnosis and we will see whether the RNFL can be used as a surrogate for magnetic resonance imaging (MRI) measure- ments of the brain." Alzheimer's disease progression is slow and can start out as MCI. Anything that aids in detection of this earlier stage as well as detects progression likely will be a boon to physicians and their patients, Dr. Coppola suggested. Researchers find OCT scans could supplement what MRIs already see C urrent ways Alzheimer's disease is diagnosed, according to the Nation- al Institute on Aging, include: patient history, memory and problem solving tests, other standard medical tests includ- ing blood and urine, and brain scans such as CT, MRI, and PET scans. But in the not-so-distant future, the retina may hold the key to un- locking a greater ability to diagnose Alzheimer's. Researchers published a meta- analysis of the potential utility of OCT for Alzheimer's disease in Au- gust 2015 in the open-access journal PLOS One. "Overall, the results of this meta-analysis showed that RNFL thickness decreased in all quad- rants in AD [Alzheimer's disease] patients," the researchers, led by Gianluca Coppola, MD, G.B. Bietti Foundation-IRCCS, Department of Neurophysiology of Vision and Neu- rophthalmology, Rome, reported. "These findings strongly suggest that degeneration of retinal ganglion cells should be added to the constel- lation of neuropathologic changes found in patients with AD on the one hand, and that RNFL [retina nerve fiber layer] thickness can be used to distinguish AD patients from normal ageing, on the other." While OCT diagnosis hasn't yet made it on more prominent, mainstream radars, a trail of peer-re- viewed evidence is being left behind that appears to be leading that way. All roads lead to retinal Rome Dr. Coppola reviewed 11 studies with 380 patients with Alzheimer's, 68 with mild cognitive impairment (MCI), a likely precursor, and 293 controls without impairment. The main findings, as measured by OCT, were: • Mean RNFL thickness was reduced in MCI compared to controls. • It was reduced even further in Alzheimer's. • RNFL in all quadrants was thinner in Alzheimer's, as well as in MCI patients (except in the superior Looking at the retina to understand Alzheimer's future

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