**5. Conclusions**

In summary, VITD could play a role in the protection of the retina and RPE from oxidative stress, inflammation, and apoptosis through the suppression of pro-inflammatory mediators and by enhancing the antioxidant defense capacity. Taking into consideration all the results we have observed, VITD could be a useful candidate in modulating the chronic low-grade inflammation and oxidative stress responsible for the complications in DR. However, further preclinical in vivo tests and DR patient clinical trials are needed to verify the therapeutic potential of VITD.

**Author Contributions:** Conceptualization, P.F.-R., S.R., M.H. and A.G.-L.; data curation, J.B.; funding acquisition, P.F.-R. and A.G.-L.; investigation, S.R. and J.B.; methodology, S.R. and M.H.; project administration, P.F.-R.; supervision, P.F.-R., S.R. and M.H.; visualization, P.F.-R., J.B. and M.H.; writing—original draft, P.F.-R., J.G.-Z. and V.B.-M.; writing—review and editing, P.F.-R., S.R., V.B.-M., M.H. and A.G.-L. All authors have read and agreed to the published version of the manuscript.

**Funding:** The present work was partially funded by Thea Laboratoires, Fundación Jesús de Gangoiti Barrera, and partially supported by RETICS (RD16/0008) from ISCIII, Ministerio de Economía y Competitividad, Spain.

**Acknowledgments:** The authors want to acknowledge Idoia Belza Zuazu and Maite Moreno Orduña for their excellent technical assistance.

**Conflicts of Interest:** A.G.-L. is a consultant for Bayer, Novartis, Allergan, Thea, and Roche. The rest of the authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.
