Interocular agreement in melanin and macular pigment optical density

Abstract

Macular pigment (MP) and melanin possibly protect the macular area by absorbing blue light and acting as antioxidants. Because little is known about the interocular correlation of melanin, we determined its optical density (MOD) in both eyes of healthy subjects using fundus reflectometry. The measuring method also provided optical densities of MP (MPOD). In addition to evaluating its interocular correspondence we checked its dependency on central retinal thickness as measured with optical coherence tomography (OCT). Spectral fundus reflectance was measured in 69 eyes of 37 healthy participants. Both eyes of 32 subjects (15 males and 17 females, aged 57.9 AE 14.6 years) were used to evaluate interocular correspondences. MPOD data from 35 right eyes of 18 males and 17 females, aged 55.7 AE 15.7 years, was used to evaluate the relation between central retinal thickness and MPOD. MOD was 0.99 AE 0.30 (range: 0.57e2.07) for the left eyes and 1.02 AE 0.28 (range: 0.62e2.07) for the right eyes. The intraclass correlation coefficient (ICC) was 0.89 (P < 0.001). MPOD was 0.49 AE 0.19 for the left eyes (range: 0.12e0.81) and 0.47 AE 0.17 (range: 0.14e0.73) for the right eyes. The ICC was 0.91 (P < 0.001). Macular retinal thickness (MRT), representing the average macular thickness in the central 1000 mm zone, was 210 AE 28 mm. Foveal retinal thickness (FRT), representing the retinal thickness at the crossing of the 6 radial scan lines on OCT, was 175 AE 34 mm. Pearson's correlation coefficient showed no significant linear association between MRT and MPOD (r ¼ À0.04, P ¼ 0.82), and between FRT and MPOD (r ¼ 0.05, P ¼ 0.78). The optical density of melanin showed a high interocular correspondence in healthy white participants. Similar results were found for MPOD. Relative interocular differences of more than 32% in MOD, or more than 34% in MPOD, may point to pathology. No relation between central retinal thickness and MPOD was found.

Spatial Profile of Macular Pigment and Its Relationship to Foveal Architecture

“…20,21,27,28 However, consistent with our findings, Kanis et al recently measured MPOD by using fundus reflectometry and foveal thickness by using OCT in 37 subjects (36 of whom were white) and found that there was no significant linear association between MFT and MPOD (r ϭ 0.05, P ϭ 0.78) or between CFT and MPOD (r ϭ Ϫ0.04, P ϭ 0.82). 28 Aleman et al 21 measured inner retinal thickness in the central 1°by using OCT in a group of 49 patients (75 eyes) with retinitis pigmentosa (RP) or Usher syndrome (US) and 19 normal subjects (27 eyes) without ocular disease. They found that MPOD (at 0.5°, measured with HFP) was positively and significantly related to retinal thickness in the patient group (r ϭ 0.57, P Ͻ 0.001) and to a lesser extent in the normal subjects (r ϭ 0.39, P ϭ 0.12).…”

Measuring macular pigment optical density in vivo: a review of techniques

“…Berendschot and van Norren [141] also used a newer version of the device, the FRA 2, which has a number of differences from the first version, including being smaller, which makes it desktop-mountable. Kanis et al [143,148] and van de Kraats and van Norren [139] have also used the FRA 2 in their studies.…”

“…Probably the most familiar optical model is that derived by van de Kraats, Berendschot and van Norren [140], which has been used to work out MPOD in several studies [e.g., 58,136,[141][142][143][144]. In essence, the density of macular pigment is determined using its known spectral characteristics, and by taking into account the amount of light reflected at the internal limiting membrane, the photoreceptor discs and the sclera [58,136,140,141,143]. The densities of the lens, melanin and blood are likewise calculated.…”

Bilateral Symmetry of Visual Function Loss in Cone–Rod Dystrophies

“…A number of studies report considerable symmetry in the central retinal features of the fellow eyes in normal subjects, including central cone photoreceptor density evaluated with adaptive optics, 31,32 optical coherence tomography measures of macular thickness, 33 macular pigment density, 34,35 and macular blood flow. 36 In light of these data, one could speculate that under the action of common mechanistic noxious determinants (such as genetic mutations, environmental and systemic factors), the likelihood of photoreceptor dysfunction and loss would have a similar retinal distribution in the two eyes of a patient, eventually resulting in bilateral symmetry of functional visual loss.…”