Influence of macular oedema on the measurement of macular pigment optical density

The purpose of this study was to determine macular pigment optical density (MPOD) in patients with macular degeneration as well as in patients with non-proliferative diabetic retinopathy.

Fifty-one phakic patients with either age-related macular degeneration (60 eyes of 30 patients; average age, 70.9 years) or non-proliferative diabetic retinopathy (42 eyes of 21 patients; average age, 61.7 years) were included in this cross-sectional study. Within the groups, patients were divided into those suffering from macular oedema and those with no oedema. An intra-subject comparison between eyes was carried out in both groups. Data were investigated on the basis of the coefficient of determination (R ²). Macular pigment optical density was measured by fundus reflectometry using the one-wavelength reflection method (Visucam 500; Carl Zeiss Meditec AG, Jena, Germany), in conformity with the method described by Schweitzer et al. (2010). We evaluated the maximum optical density in the measurement area (max OD) and the average optical density across the reference area in the measurement area (mean OD). Specifically, the influence of macular oedema on macular pigment optical density was examined. The subsequent measurement of retinal thickness was carried out by spectral-domain optical coherence tomography (Spectralis SD-OCT, Heidelberg Engineering GmbH, Heidelberg, Germany).

The current study included two groups. The first group consisted of patients with non-proliferative diabetic retinopathy, as follows: no macular oedema on either side (max OD: R ² = 43.2 %, p = 0.16; mean OD: R ² = 68.7 %, p = 0.04); one-sided macular oedema (max OD: R² = 16 %, p = 0.60; mean OD: R² = 100 %, p = 0.04); or macular oedema in both eyes (max OD: R² = 79.7 %, p < 0.01; mean OD: R² = 81.4 %, p < 0.01). The second group comprised patients with age-related macular degeneration (AMD), as follows: non-exudative changes on both sides (max OD: R² = 64.0 %, p = 0.20; mean OD: R ² = 16 %, p = 0.60); one-sided exudative macular changes (max OD: R ² = 50.6 %, p < 0.01; mean OD: R ² = 20.8 %, p = 0.04); or exudative macular degeneration on both sides (max OD: 3 R ² = 6.0 %, p = 0.29; mean OD: R ²= 81.0 %, p = 0.04). The data available presented a correlation of MPOD values of both eyes of an individual within the groups investigated. In this respect, the data of the partner eyes within the group of patients with diabetic retinopathy were more highly correlated with each other than the values of both eyes of patients suffering from age-related macular degeneration.

The present study showed that macular oedema did not seem to have an influence on a valid measurement of MPOD by one-wavelength fundus reflectometry. Thus, meaningful data could also be obtained on patients with exudative retinal changes.