Nanoemulsions for the ocular delivery of anti-infectives: challenges, advances and prospects in treating infectious eye diseases

Infectious diseases constitute a significant health burden globally, especially with the widespread emergence of antimicrobial resistance. Infectious eye diseases, usually characterised by inflammation, redness of the eye, ocular tissue destruction and vision impairment, may be caused by bacteria, viruses, fungi or parasites. Early diagnosis and effective treatments are necessary to prevent severe visual impairment and blindness in patients. The conventional treatment strategy is using topically or systemically administered antimicrobial agents alone or in combination with steroidal agents. However, the bioavailability of drugs administered topically or systemically is very low due to the barriers presented by the anatomy and physiology of the eye, which militate against the penetration of drugs into intraocular tissues. Local injections directly into intraocular tissues improve the bioavailability of drugs in the eye. Nonetheless, this approach may lead to ocular tissue damage and secondary infections. Nanoemulsions have shown prospects as an effective strategy to overcome the drawbacks of conventional ocular delivery systems. This review discusses various infectious eye diseases and the challenges encountered in their treatments. The formulation techniques and recent studies on the use of nanoemulsions in the treatment of infectious eye diseases are also discussed. Finally, the challenges and recent technological advancements in nanoemulsion design are highlighted. Nanoemulsions, as novel nanomedicines, have a lot of potential in ocular drug delivery, offering advantages such as increased solubility, enhanced residence time on the ocular surface, and improved penetration through the ocular barriers. Nanoemulsions show great potential in treating infectious eye diseases and reducing the incidence of avoidable vision impairment and blindness.