Dry eye syndrome and allergic conjunctivitis are the most common inflammatory disorders of the eye surface. Although eye drops are the most usual prescribed dosage form, they are characterized by low ocular availability due to numerous barrier mechanisms of the eye. The use of biopolymers in liquid ophthalmic preparations has numerous advantages, such as increasing the viscosity of the tear film, exhibiting bioadhesive properties, and resisting the drainage system, leading to prolonged retention of the preparation at the site of application, and improvement of the therapeutic effect. Some mucoadhesive polymers are multifunctional excipients, so they act by different mechanisms on increasing the permeability of the cornea. Additionally, many hydrophilic biopolymers can also represent the active substances in artificial tear preparations, due to their lubrication and moisturizing effect. With the modification of conventional ophthalmic preparations, there is a need for development of new methods for their characterization. Numerous methods for the assessment of mucoadhesiveness have been suggested by the literature. This review gives an overview related to the development of mucoadhesive liquid ophthalmic formulations for the treatment of dry eye and allergic conditions.
