Abstract
Purpose :
To study relationships between age, serum neurofilament light (s-NfL), and thickness of inner retinal layers in the canine area centralis and flash-VEP (FVEP) peak times.
Methods :
Eye examination including slit-lamp biomicroscopy, ophthalmoscopy and tonometry was performed in 12 beagles and 1 Labrador retriever aged 2-12 years. Dogs were subdivided into 3 groups: young (Y; < 9 years), old (O; 9-11 years) and very old (VO; >11 years). Cognitive performance was evaluated using standard questionnaires and interviews. Ganglion cell complex (GCC) and nerve fiber layer (RNFL) thickness in 4 locations around and in the fovea equivalent were measured using OCT. Furthermore, simultaneous ERGs and FVEPs were recorded under light sedation. S-NfL was analyzed using single molecular array (Simoa) technique.
Results :
Dogs in the VO-group were considered to be at risk for or show signs of mild canine cognitive impairment (CI). S-NfL increased with age (R2=0.70, P<0.001). Using nested linear models, GCC reasonably well predicted both age and s-NfL (R2=0.57, P<0.001 and R2=0.59, P<0.001, respectively). Neither age nor s-NfL were significantly related to RNFL regardless of position. Screening showed positive correlations between s-NfL and contralateral peak times for N2 through N5 (R2 from 0.42 to 0.69; P-values 0.0008 to 0.017), whereas age was positively correlated to the same peaks, except P4 (R2 from 0.33 to 0.75; P-values from 0.0012 to 0.042). Only peak times for P5 and N5 were significantly longer in the VO-group compared to both the O- and Y-group, whereas other peak times were not significantly different between O and VO dogs.
Conclusions :
Age and s-NfL are positively correlated in dogs and a trend towards increasing concentrations of s-NfL between each age group was seen, although differences between O and VO dogs were not significant in this pilot study. Both age and s-NfL were reasonably well correlated to GCC but not to RNFL. GCC in and around the fovea equivalent seems less suitable being a solitary biomarker for early or mild CI as we found no difference between the two oldest age groups. FVEP peak times were positively correlated to s-Nfl (and also to age). Peak time of late wavelets, P5 and N5, increased significantly between groups and the significant difference between the two oldest age groups indicates that these parameters may have a role as biomarkers for early/mild canine CI.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.