Macular Pigment Carotenoid Supplementation for the Preservation of Visual Structure and Function Following a Collegiate Rugby Season

Abstract

Introduction: Repetitive head impacts (RHIs) and visual system dysfunction are often associated. Interventions to prevent or limit visual deficits following RHIs are not well understood. This study examined visual structure and function following exposure to RHIs and the effectiveness of a supplemental intervention of macular pigment carotenoids (MPCs) and omega-3 fatty acids in attenuating visual changes from pre- to post-season in collegiate rugby players. Additionally, blood biomarkers associated with neurodegeneration were examined.

Methods: Optical coherence tomography measured visual structure through ganglion cell complex (GCC) and retinal nerve fiber layer (RNFL) thickness. Bioavailability of the supplement was assessed through skin carotenoid concentration (SC). Contrast sensitivity (CS) and critical flicker-fusion frequency (CFF) were used to measure visual function. NF-L, GFAP, Tau, and UCH-L1 concentrations in blood samples were analyzed.

Results: Thirty-one rugby players (15M/16F; 19±1.4 years) were randomly assigned to supplement (n = 15) or placebo (n = 16) groups. Left eye GCC inferior region was thinner at post-season in supplement (102.1±4.4 vs 102.9±4.7 μm; p = 0.002) and placebo groups (101.4±5.3 vs 102.6±5.0 μm, p < 0.001). The supplement group had a higher SC score at post-season versus the placebo group (409.2±76.3 vs 323.4±61.3; p = 0.04). With regards to visual function, CFF approached a significant increase in the supplemental group versus placebo (27.6±1.8 vs 25.7±2.2 Hz, p = 0.08), but there were no differences found between groups in MPOD or CS. NF-L was different at post-season in the placebo (10.05 vs 7.21 pg/mL; p = 0.003) but not the supplement group (7.07 vs 7.78 pg/mL; p = 0.40). Tau was different between groups at pre- (1.2 vs 0.87 pg/mL; p = 0.04) and post-season (1.33 vs 1.01 pg/mL; p = 0.02) with greater concentrations in the supplement group. GFAP and UCH-L1 were not different. One season of collegiate rugby resulted in retinal thinning and increased concentrations of NF-L and Tau. Supplementation with MPCs and omega-3s may be useful in limiting retinal thinning and preventing increases in biomarkers of neurodegeneration.

Keywords: Macular pigment carotenoids; collision sports; repetitive head impacts; visual system.

Figure 1

Thickness of the Ganglion Cell Complex and Retinal Nerve Fiber Layer inferior and superior regions for both the left (OS); (A–D) and right (OD); (E–H) eyes at pre-season (open circles) and post-season (blue circles) testing in supplement and placebo groups. * p < 0.05 compared to pre-season.

Figure 2

Measurements of total skin carotenoid concentration at pre-season (open circles) and post-season (blue circles) testing in supplement and placebo groups. *p < 0.05 compared to pre-season; # p < 0.05 compared to post-season between groups.

Figure 3

Contrast sensitivity scores for mesopic (A–D) and photopic (E–H) trials at pre-season (open circles) and post-season (blue circles) testing in supplement and placebo groups.

Figure 4

Macular pigment optical density (A) and critical flicker-fusion frequency (B) scores at pre-season (open circles) and post-season (blue circles) testing in supplement and placebo groups.

Figure 5

(A) NF-L, (B) GFAP, (C) Tau, and (D) UCH-L1 concentrations at pre-season (white) and post-season (blue) testing in supplement and placebo groups. Boxes represent first and third quartiles with median values denoted by the horizontal lines, and whiskers indicate minimum and maximum observations. n = 14 (supplement) and n = 16 (placebo) for NF-L, GFAP, and Tau. n = 11 (supplement) and n = 13 (placebo) for UCH-L1. * p < 0.05 compared to pre-season. # p < 0.05 compared to pre-season between groups and ## p < 0.05 compared to post-season between groups.

Figure 6

(A) NF-L, (B) GFAP, (C) Tau, and (D) UCH-L1 change score concentrations from pre-season to post-season in supplement (yellow) and placebo (green) groups. Boxes represent first and third quartiles with median values denoted by the horizontal lines, and whiskers indicate minimum and maximum observations. n = 14 (supplement) and n = 16 (placebo) for NF-L, GFAP, and Tau. n = 11 (supplement) and n = 13 (placebo) for UCH-L1.