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Purpose@#This study aimed to assess the difference in the vascular parameters of perfusion in the optic nerve head in normal tension glaucoma (NTG) across disease stages using optical coherence tomography angiography and its correlation with peripapillary retinal nerve fiber layer (RNFL) thickness. @*Methods@#In this retrospective study, 83 eyes with varying stages of NTG (25 mild, 31 moderate, and 27 severe) and 90 healthy eyes were enrolled. The perfusion density (PD) and flux index (FI) of the optic nerve head divided into four sectors were determined. We compared the vascular, structural, and functional parameters between normal and glaucomatous eyes and performed a subgroup analysis among the NTG stages. Pearson correlation coefficient was used to assess the topographic correlation between vascular parameters and RNFL thickness. @*Results@#PD and FI were significantly decreased in the NTG group. Subgroup analysis revealed a significant decrease in vascular parameters in most regions in the NTG group, except for the nasal PD and temporal FI. Post hoc analysis showed a significant decrease in PD in the inferior region across all severity levels (mild vs. moderate, p = 0.012; moderate vs. severe, p = 0.012; mild vs. severe, p < 0.001). PD and FI were strongly correlated with RNFL thickness in all quadrants (all p < 0.001), with the strongest correlation observed in the inferior region. @*Conclusions@#Vascular parameters were significantly decreased in glaucomatous eyes, and the degree of decrease in vascular parameters was proportional to glaucoma severity. Peripapillary perfusion analysis using optical coherence tomography angiography may complement other measurements used for glaucoma diagnosis.
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PURPOSE: In this study we investigated the safety level of the national standard for tinted soft contact lenses by comparing the standards in various countries. METHODS: To evaluate the current guidelines for tinted soft contact lenses such as form and appearance, diameter, curvature radius, vertex power, cylindrical refractivity and cylindrical axis, luminous/ultraviolet ray (UV) transmittance, moisture content, oxygen permeability coefficient, extractables, elution test, cytotoxicity, sensitization, eye irritation test, acute systemic/subchronic/subacute toxicity, genotoxicity and biocompatibility safety test using rabbit eyes and sterility test. We compared the standards of International Organization for Standardization (ISO), Food and Drug Administration (FDA) of the United States, Ministry of Health, Labor and Welfare (MHLW) of Japan and Ministry of Food and Drug Safety (MFDS) of Korea. RESULTS: The guidelines for tinted soft contact lenses of ISO, FDA and MFDS are similar to soft contact lenses but MHLW of Japan classifies these lenses and sets specific guidelines. First, the oxygen permeability coefficient measured at 6mm from the center should be maintained over 80%. Also, coloring should not affect the oxygen permeability coefficient significantly. Regarding the physical (form and appearance, diameter, curvature radius, moisture content) and optical (vertex power, cylindrical refractivity and cylindrical axis, luminous/UV transmittance, oxygen permeability coefficient) characteristics, no differences were found between ISO and MFDS. However, several differences were found in chemical characteristics (extractables, elution test) and biological stability (cytotoxicity, sensitization, eye irritation test, acute systemic/subchronic/subacute toxicity test, genotoxicity, biocompatibility safety test using rabbit eyes, sterility test). For example, the elution test is required only by MFDS. CONCLUSIONS: The reinvestigation into the effectiveness of the elution test is needed and new evaluation measures including scanning electron microscopy and atomic force microscopy designed for tinted soft contact lenses to evaluate the size of the optical area, the location and roughness of the pigmented layer are required.