Macular pigment (MP) is composed of lutein, zeaxanthin, and meso-zeaxanthin, which accumulate mainly at the macula. MP has antioxidant function and can filtering blue wave. Measurement of MP is about its optical density, that is, macular pigment optical density (MPOD). This review summarizes the function and clinical use of MP and MPOD. Researches has show that MPOD is related to some ocular disease such as age-related macular degeneration, macular telangiectasia type 2, diabetic retinopathy, Stargardt disease et al. MPOD can be used in the judgment of clinical diagnosis, treatment effect. The specific mechanism of MP metabolism in the retina and in the pathogenesis of the disease, genotype specific nutritional therapy of xanthophyll, the establishment of a database combined with artificial intelligence and the rapid and convenient MP determination are all issues of great contention that need to be resolved.
Objective To observe the changes of macular microvascular structure and macular pigment density (MPOD) in eyes with macular edema (ME) secondary to retinal vein occlusion (RVO), and preliminarily analyze their correlation. MethodsA prospective clinical study. A total of 62 eyes of 62 patients with monocular RVO secondary ME (RVO-ME) diagnosed in the Ophthalmology Hospital of Xi'an No.1 Hospital from July 2020 to May 2021 were included in this study. There were 33 males with 33 eyes, 29 females with 29 eyes. The age was 58.30±12.15 years. The course of disease from the onset of symptoms to medical treatment was 12.29±7.65 days. All patients underwent best corrected visual acuity (BCVA), optical coherence tomography angiography (OCTA) and MPOD test. BCVA examination was performed using a standard logarithmic visual acuity chart, which was converted to logarithm of minimum angle of resolution (logMAR). The vascular density (VD), vascular skeletal density (SD), foveal avascular area (FAZ) and central macular thickness (CMT) of the superficial retinal capillary plexus (SCP) in the range of 3 mm×3 mm in the macular area of bilateral eyes were measured by OCTA. MPOD was measured by heterochromatic scintillation photometry. Bilateral eyes passed examination in 37 cases. The eyes of 25 patients failed to pass the test. The changes of macular VD, SD, FAZ area, CMT and MPOD between the affected eyes and the contralateral eyes were compared. The MPOD of the affected eye and the contralateral eye was compared by paired t test. FAZ area, CMT, VD, SD, and logMAR BCVA were tested by paired Wilcoxon signed rank sum test. Spearman rank correlation test was used to analyze the correlation between macular blood flow density (VD, SD) and foveal morphology (FAZ area, CMT) with logMAR BCVA and MPOD. ResultsCompared with contralateral eyes, VD (Z=－5.981) and SD (Z=－6.021) were decreased, FAZ area (Z=－2.598) and CMT (Z=－6.206) were increased, and the differences were statistically significant (P＜0.05). In 37 patients who passed MPOD test in bilateral eyes, the MPOD value of the affected eye was lower than that of the contralateral eye, and the difference was statistically significant (t=－2.930, P＜0.05). Compared with the affected eye which failed to pass the MPOD detection, macular VD (Z=－2.807) and SD (Z=－2.460) were increased, FAZ area (Z=－4.297) and CMT (Z=－3.796) were decreased in the affected eye which passed the MPOD test, and the differences were statistically significant (P＜0.05). Correlation analysis showed that logMAR BCVA in the affected eye was negatively correlated with macular VD and SD (r=－0.298, －0.461; P＜0.05), which was positively correlated with FAZ area and CMT (r=0.487, 0.789; P＜0.05). MPOD in the affected eye was negatively correlated with logMAR BCVA (r=－0.344, P＜0.05). MPOD in the contralateral eye was positively correlated with CMT (r=0.358, P＜0.05). ConclusionsThe VD and SD of macular SCP are decreased, FAZ area is enlarged, CMT is thickened, and MPOD is decreased in RVO-ME eyes. MPOD is negatively correlated with logMAR BCVA.