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Denise A. Valenti; Alzheimer’s Disease: Frequency Doubling Technology Biomarkers in the Visual System. Invest. Ophthalmol. Vis. Sci. 2012;53(14):4845.
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This study was to investigate the use of Frequency Doubling Technology ( FDT) visual field testing to identify early functional biomarkers of Alzheimer’s disease (AD) in patients diagnosed with AD presenting for care in a neurology practice and comparing the findings with participants not diagnosed with AD. It was not the intent to correlate the biomarker with severity of disease, but to determine if the biomarker was present in a pass/fail format.
Adult patients attending clinics at the Boston University Neurology Associates were invited to participate. Adults accompanying patients were invited to participate as control participants. The screening included an ocular history, cognitive history, monocular distance visual acuities and FDT utilizing the 20-1 threshold strategy. A fail was if any of the targets was recorded (using the instrument normative screening printout) as having a probability of P < 2% or any two or more targets having a P < 5% as identified in the FDT printout (results based on the technology internal normative database).
The results from each eye of participants with a diagnosis of AD (N eyes screened=27, average age 81) and each eye of control participants (N eyes screened=18, average age 68) were reviewed. After controling for reliability there were twenty tests for the AD. Seventeen of the twenty reliable FDT tests obtained from AD participants were failed FDT tests. Five failed FDT were attributed to glaucoma and two failures could be accounted for by dense cataracts (confirmed by ophthalmoscopy), Ten FDT failures were not associated with any reported ocular pathology. Of eighteen eyes screened with FDT in the control participant group there was only one unreliable test and only one failed FDT. The one failed FDT was in a participant reporting long standing diabetes.
The average age of the control group was ten years younger than AD group. However, the age difference is not likely to fully account for the differences in failure rate with FDT. There was a failure rate of 85% in the participants with AD while only 6% of the control group failed the screening. Given the ease and efficiency that screening with FDT presents, such technology may prove to be an effective means of identifying age related neurodegenerative processes affecting the visual system. Screening with FDT not only can be an integral part of the early identification of age related eye disease, but also neurodegenerative disease impacting the visual system such as AD.
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