The epigenetic modification of nucleic acids represents one of the most significant areas of study in the field of nucleic acids because it makes gene regulation more complex and heredity more complicated, thus indicating its profound impact on aspects of heredity, growth, and diseases. The recent characterization of epigenetic modifications of DNA and RNA using chemical labelling strategies has promoted the discovery of these modifications, and the newly developed single-base or single-cell resolution mapping strategies have enabled large-scale epigenetic studies in eukaryotes. Due to these technological breakthroughs, several new epigenetic marks have been discovered that have greatly extended the scope and impact of epigenetic modifications in nucleic acids over the past few years. Because epigenetics is reversible and susceptible to environmental factors, it could potentially be a promising direction for clinical medicine research. In this review, we have comprehensively discussed how these epigenetic marks are involved in disease, including the pathogenesis, prevention, diagnosis and treatment of disease. These findings have revealed that the epigenetic modification of nucleic acids has considerable significance in various areas from methodology to clinical medicine and even in biomedical applications.

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ObjectivesTo investigate vascular flow density in pathological myopia with optical coherence tomography (OCT) angiography.DesignA prospective comparative study was conducted from December 2015 to March 2016.SettingParticipants were recruited in Beijing Tongren Hospital.ParticipantsA total of 131 eyes were enrolled, which were divided into three groups: 45 eyes with emmetropia (EM; mean spherical equivalent (MSE) 0.50D to −0.50D), 41 eyes with high myopia (HM; MSE ≤−6.00D, without pathological changes), and 45 eyes with pathological myopia (PM; MSE ≤−6.00D and axial length (AL) ≥26.5 mm, and with pathological changes).Main outcome measuresMacular, choriocapillaris and radial peripapillary capillary (RPC) flow densities were measured and compared between groups, and their relationships with AL and best corrected visual acuity (BCVA) were analysed.ResultsSignificant differences were found in macular, choriocapillaris and RPC flow densities among the three groups (p<0.05). Multiple comparisons revealed that, compared with the EM and HM groups, macular and RPC flow densities of the PM group were significantly decreased (p<0.05), but no significant difference in choriocapillaris flow density was found between the PM and HM groups (p=0.731). Compared with the EM group, retinal flow density in the macular and arcuate fibre region was not decreased in the HM group. In addition, there was a negative correlation between AL and superficial macular flow density (β=−0.542, p<0.001), deep macular flow density (β=−0.282, p=0.002) and RPC flow density (β=−0.522, p<0.001); and a positive correlation between BCVA and superficial macular flow density (β=0.194, p=0.021), deep macular flow density (β=0.373, p<0.001), and choriocapillaris flow density (β=0.291, p=0.001).ConclusionsMacular and RPC flow densities decreased in pathological myopia compared with high myopia and emmetropia. No significant decrease of retinal flow density in the macular and arcuate fibre region was found in high myopic eyes compared with emmetropic eyes. Moreover, macular and RPC flow densities were negatively related to AL, and macular flow density was positively related to BCVA.