Correlation between Macular Pigment Optical Density and Neural Thickness and Volume of the Retina

Abstract

Macular pigment (MP), which is composed of lutein/zeaxanthin/mezo-zeaxanthin, is concentrated in the central part of the retina, the macula. It protects the macula by absorbing short-wavelength light and suppressing oxidative stress. To evaluate whether MP levels are related to retinal neural protection and resulting health, we analyzed the association between the MP optical density (MPOD), and the macular thickness and volumes. Forty-three eyes of 43 healthy adult volunteers (21 men and 22 women; age: 22-48 (average 31.4 ± 1.1) years) were analyzed. Highly myopic eyes (<-6 diopters) were excluded. MPOD was measured using MPS2®, and the neural retinal thickness and volume were measured using optical coherence tomography. The mean MPOD was 0.589 ± 0.024, and it positively correlated with the central retinal thickness (P = 0.017, R = 0.360) and retinal volume of the fovea (1-mm diameter around the fovea; P = 0.029, R = 0.332), parafovea (1-3-mm diameter; P = 0.002, R = 0.458), and macula (6-mm diameter; P = 0.003, R = 0.447). In the macular area (diameter: 6 mm), MPOD was correlated with the retinal neural volume of the ganglion cell layer (P = 0.037, R = 0.320), inner plexiform layer (P = 0.029, R = 0.333), and outer nuclear layer (P = 0.020, R = 0.353). Thus, MPOD may help in estimating neural health. Further studies should determine the impact of MP levels on neuroprotection.

Keywords: macula; macular pigment; neural tissue; optical coherence tomography; retina.

Figure 1

Correlation between the central retinal thickness (CRT), central choroidal thickness (CCT), and macular pigment optical density (MPOD). (A) Correlation of MPOD between the right and left eyes of the individuals was confirmed. (B) A positive correlation was seen between CRT and MPOD. The arrow in the OCT image indicates CRT. (C) No significant correlation was seen between CCT and MPOD. The arrow in the OCT image indicates CCT. ** P <0.01, * P <0.05.

Figure 2

Correlations of the foveal, parafoveal, and macular volumes with the macular pigment optical density (MPOD). MPOD positively correlated with the retinal neural volumes of the fovea (1-mm diameter shown in blue; P = 0.029, R = 0.332, A), parafovea (1–3-mm diameter shown in green; P = 0.002, R = 0.458, B), and macula (6-mm diameter shown in gray; P = 0.003, R = 0.447, C). * P < 0.05, ** P < 0.01.

Figure 3

Correlation between the macular pigment optical density (MPOD) and volumes of retinal neural layers. (A) The macular area (left, the largest circle) was analyzed to calculate the volume of each retinal layer (right, upper), and the values obtained in each area (right, lower) were summed up to determine the values in the macular area (6-mm diameter). (B-D) MPOD was positively correlated with the retinal volumes of GCL (B), IPL (C), and ONL (D) in the macular area. RNFL retinal nerve fiber layer; GCL, ganglion cell layer; IPL, inner plexiform layer; INL, inner nuclear layer; OPL, outer plexiform layer; ONL, Outer nuclear layer; RPE, retinal pigment epithelium. * P < 0.05.