Nanotechnology-based ocular drug delivery systems: recent advances and future prospects.

Ocular drug delivery has constantly challenged ophthalmologists and drug delivery scientists due to various anatomical and physiological barriers. Static and dynamic ocular barriers prevent the entry of exogenous substances and impede therapeutic agents' active absorption. This review elaborates on the anatomy of the eye and the associated constraints. Followed by an illustration of some common ocular diseases, including glaucoma and their current clinical therapies, emphasizing the significance of drug therapy in treating ocular diseases. Subsequently, advances in ocular drug delivery modalities, especially nanotechnology-based ocular drug delivery systems, are recommended, and some typical research is highlighted. Based on the related research, systematic and comprehensive characterizations of the nanocarriers are summarized, hoping to assist with future research. Besides, we summarize the nanotechnology-based ophthalmic drugs currently on the market or still in clinical trials and the recent patents of nanocarriers. Finally, inspired by current trends and therapeutic concepts, we provide an insight into the challenges faced by novel ocular drug delivery systems and further put forward directions for future research. We hope this review can provide inspiration and motivation for better design and development of novel ophthalmic formulations.

Corrections of fast neutron inelastic scattering effects on D-T neutron porosity logging.

With the continuous development of logging tools with controllable neutron sources, improving the processing method to make their measurements more consistent with those obtained by chemical sources has become a development trend in well logging based on controllable sources. To study the correction method that is not constrained by other parameters and does not require chemical sources, the reasons for the differences in the neutron porosity responses of D-T and chemical sources are theoretically analyzed. Then the fast neutron slowing-down process is divided into two stages depending on neutron energy. A method to correct the effects of inelastic scattering in D-T neutron porosity is established through the derivation of the theoretical relationship. Finally, the effectiveness of the correction method is verified using the simulation and measured data. The results show that after inelastic scattering correction, the measurement results of neutron porosity logging with controllable and chemical sources are highly consistent, and there is a close correspondence between the two types of sources in terms of measured data. Therefore, the proposed inelastic scattering correction method can effectively replace density correction to make the measurement results of the D-T neutron source more consistent with those of chemical sources. This study is of great significance for the wide application of neutron porosity measurement with controllable neutron sources and the replacement of radioactive sources in logging tools in the future.

Corneal endothelial cell density and its correlation with birth weight, anthropometric parameters, and ocular biometric parameters in Chinese school children.

BACKGROUND: To describe the distribution of corneal endothelial cell density (ECD), and to explore its correlation with birth weight (BW), anthropometric parameters, and ocular biometric parameters in Chinese school children. METHODS: In the population-based cross-sectional Nanjing Eye Study, children were measured for anthropometric information, for ECD by the noncontact specular microscope and for ocular biometric parameters by the optic low-coherent reflectometer. Data from right eyes were analyzed to illustrate the distribution of ECD and for determining correlated factors with ECD using univariate and multiple linear regression analysis. Comparisons among three different BW groups were performed using a one-way ANOVA analysis followed by the Bonferroni correction for pairwise comparisons. RESULTS: Of 1171 children, the mean (± standard deviation) ECD was 2875.34 ± 195.00 cells/mm2. In the Multiple Linear Regression analysis, BW, gender and central corneal thickness were significantly associated with ECD. The ECD increased by 36.16 cells/mm2 with BW increasing by 1 kg (P = 0.001) and increased by 0.44 cells/mm2 for every additional 1 mm in central corneal thickness (P = 0.01). The ECD of girls was 54.41 cells/mm2 higher than boys (P < 0.001). Children born with low BW presented significantly lower ECD than those born with normal BW (P < 0.05) and high BW (P < 0.05). Age and axial length were not significantly associated with ECD (P = 0.06 and P = 0.21, respectively). CONCLUSIONS: In Chinese school children aged 82 to 94 months, the ECD is positively correlated with BW and central corneal thickness, in which BW is a newly identified associated factor. It is like that gender plays an important role in ECD distribution while girls have relatively greater ECD than boys.