Retinal Neurodegenerative Signs in Alzheimer's Diseases

Retinal Neurodegenerative Signs in Alzheimer's Diseases

A few studies suggest that patients suffering from neurodegenerative diseases (such a multiple sclerosis or Alzheimer's disease (AD)) show decreased thickness of the retinal nerve fiber layer (RNFL), indicating axonal degeneration. High-definition spectral domain optical coherence tomography (SD-OCT), performed without radiation in a few seconds per eye, offers a precise and standardized estimation of this parameter, which could constitute a biomarker for cerebral axonal degeneration. These RNFL deficits might even be the earliest sign of AD, prior to damage of the hippocampal region that impacts memory.

Besides, some associations of AD with some degenerative diseases of the eye (glaucoma, microvascular abnormalities, age-related macular degeneration (AMD)) have also been reported.

It therefore seems interesting to determine whether RNFL thickness, and other ocular parameters, may give some indications for a better detection of AD and cognitive decline in the elderly.

Inclusion Criteria:

• Inclusion criteria for AD cases:
• Diagnosis of probable AD, defined according to the NINCDS-ARDRA criteria51
• Light to moderate severity of the disease, defined by a MMSE score >10 (global evaluation of cognition)
• Patient aged 50 years or more
• Patient benefiting from social insurance

Inclusion criteria for controls:

• Absence of suspicion of dementia, based on normal performance according to age and educational level at neuropsychological testing defined as:
• Free recall ≥17 and total recall ≥40 for the Free and Cued Selective Reminding Test (Grober and Buschke test 52) MMSE ≥ norm for age and educational level (defined by mean - 1 SD)
• Isaac's set test ≥ norm for age and educational level (defined by mean - 1 SD)
• Matched to age and gender of the cases
• Patient benefiting from social insurance

Exclusion Criteria:

Exclusion criteria for all patients :

• History of Parkinson's disease or other neurodegenerative disorder
• History of Horton's disease
• History of inflammatory neuropathies (in particular Devic's disease, multiple sclerosis)
• History of vascular ischemic neuropathies and chronic intracranial hypertension
• History of pituitary tumors
• Presence of diseases (systemic and/or ocular diseases) or behavioural or cognitive symptoms incompatible with eye examination
• Known diabetes
• Person under tutorship or curatorship, person unable to express consent

Additional exclusion criteria for AD cases:

• Dementia of other cause than AD
• Severe AD, defined by MMSE score ≤ 10

Additional exclusion criteria for controls:

• Presence of dementia, of whatever cause