Retinal neuronal loss detected by swept-source optical coherence tomography in patients with mild cognitive impairment

Abstract

Purpose : Mild cognitive impairment (MCI) is a clinical condition in which subjects present memory loss that greater than expected for their age but not enough to impair their daily activities. Many authors consider MCI an early stage of Alzheimer disease (AD) and monitoring the clinical status in addition to ancillary objective tests are required to document a possible progression of MCI to AD. Peripapillary RNFL and macular thickness measurements using OCT may turn out to be a non-invasive in vivo marker in both MCI and AD patients. Our purpose was to evaluate the ability of swept-source OCT (SS-OCT) estimate retinal neural loss in eyes of patients with MCI. We also assessed the possible relationship between the cognitive impairment and SS-OCT measurements is such patients.

Methods : SS-OCT scans were obtained in 40 eyes of 20 patients with MCI and 40 control eyes. Peripapillary RNFL, macular full-thickness and segmented inner layers thickness parameters were calculated. Inner layers macular thickness parameters included: the macular RNFL (mRNFL), the ganglion cell layer plus inner plexiform layer thickness (GCL+), and the RNFL plus the GCL+ (GCL++). The Mini-Mental State Examination (MMSE) was used to assess cognition. The two groups were compared and the relationship between MMSE scores and SS-OCT measurements in MCI patients was verified.

Results : There was no significant difference between peripapillary RNFL thickness measurements in MCI eyes when compared to controls. All full-thickness macular measurements were smaller in MCI eyes when compared to controls, but only reached significant difference in the temporal inner and outer and the inferior inner segments. mRNFL and GCL++ thickness measurements, were also significantly reduced in MCI eyes. A significant correlation was found between most SS-OCT parameters and the MMSE score.

Conclusions : Our results suggests that macular thickness measurements reduction, mostly in the inner retinal layers, obtained by the SS-OCT reflect a neural loss in MCI patients with similar pattern of impairment that was already demonstrated in patients with AD, suggesting that neuronal loss in both conditions are pathophysiologically related. Moreover, such neuronal loss was well with the cognitive impairment in MCI patients. Our results suggest that SS-OCT could be a potentially useful diagnostic tool in the management of MCI patients.

This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.