Evidence is accumulating that cognitive function, and visual impairment may be related.
In this pilot study, we investigated whether multifractal dimension and lacunarity
analyses performed in sectoral regions of the retina may reveal changes in patients
with cognitive impairment (CI) that may be masked in the study considering the whole
retinal branching pattern. Prospective age-matched subjects (n = 69) with and with
no CI and without the presence of any ophthalmic history were recruited (age > 55+
years). The Montreal Cognitive Assessment (MoCA) was used to measure CI, and full-field
electroretinogram (ERG) was performed. Also, visual performance exams were conducted
using the Rabin cone contrast test (CCT). Quantification of the retinal structure
was performed in retinal fundus images [45(o) field of view (FOV), optic disk centered]
with excellent quality for all individuals [19 healthy controls (HC) and 20 patients
with CI] after evaluating the inclusion and exclusion criteria in all study participants
recruited (n = 69). The skeletonized vasculature network that comprised the whole
branching pattern observable in the full 45 degrees FOV was obtained for each image
and divided into nine equal regions (superotemporal, superior, superonasal, macular,
optic disk, nasal, inferotemporal, inferior, and inferonasal). The multifractal behavior
was analyzed by calculating the generalized dimension Dq (Do, D1, and D2), the lacunarity
parameter (?), and singularity spectrum f(alpha) in the nine sectoral skeletonized
images as well as in the skeletons that comprised the whole branching pattern observable
in the full 45 degrees FOV. The analyses were performed using the ImageJ program together
with the FracLac plug-in. Independent sample t-tests or Mann Whitney U test and Pearson
correlation coefficient were used to find associations between all parameters in both
groups. The effect size (Cohen's d) of the difference between both groups was also
assessed. A p-value < 0.05 was considered statistically significant. Significant correlations
between multifractal and ? parameters with the MoCA and implicit time ERG-parameter
were observed in the regional analysis. In contrast, no trend was found when considering
the whole retinal branching pattern. Analysis of combined structural-functional parameters
in sectoral regions of the retina, instead of individual retinal biomarkers, may provide
a useful clinical marker of CI.
