Due to their sun and oxygen exposure, the eyes are especially susceptible to oxidative stress, which causes several ocular pathologies. One of the antioxidants that is most present in the eyes to fight oxidative stress is glutathione, the defecit of which is linked to several ophthalmologic diseases. The research group of the CEU UCH of Valencia headed by professor Alicia López Castellano and specialized in developing new pharmaceutic means for the administration of medicines via transdermic or ophthalmic techniques, has designed a new ocular insert to administer antioxidants through the cornea and the sclera of the eye. Their study, published in Pharmaceutics, analyzes the benefits of this new method of administration compared to traditional ophthalmic drops.
CEU UCH Professor María Sebastián, member of the research team, says, “The anatomic and physiologic structure of the eye represents, in itself, an important barrier for the administration of medicines. The amount of medicine that breaks through the cornea or sclera when using drops, gels or creams, is very limited, making it necessary to develop more efficient alternative methods. This is why we have been working for several years on the development of bioadhesive ocular inserts to treat ocular diseases, increasing the time that the medicine remains in the eye, and so that it may be released gradually, thus penetrating the ocular tissues better.” Following their work on the administration of antibiotics through the cornea with this type of inserts, in this last study the team has tested the administration of an antioxidant, this time through the cornea and sclera, using the same type of inserts.
Ocular antioxidants, combined
As the CEU UCH researchers explain in the study, glutathione is the most available natural antioxidant in the eyes, and a deficit is linked to pathologies of the retina, the human tissue that consumes the most oxygen: Hence the need to for better protection against oxidative stress via glutathione.
The ability to generate this antioxidant decreases with age, which can favor the appearance of ocular pathologies such as diabetic retinopathy, glaucoma or macular degeneration linked to aging. The lack of glutathione is also associated to the appearance of cataracts and hereditary degenerative diseases, such as retinitis pigmentosa. “In this case, we have collaborated with the team headed at the CEU UCH by professor María Miranda, who had already studied the beneficial effect of glutathione to slow down the cellular death of the photoreceptors in an experimental model of this disease,” adds María Sebastián.
The insert as a new pharmacological method
The study shows that the created ocular insert is able to release the antioxidant in the eye. One of the advantages of these inserts is that they can be applied less times than ophthalmic drops, as well as controlling the release of the medicine, providing a more comfortable administration for the patient. To design the best ophthalmic insert possible, the research team has studied the diffusion of glutathione through the cornea and sclera using a rabbit’s eye as an animal model. Furthermore, they have verified that glutathione does not cause an irritation of the ocular mucosa and that it can be stored preserving its properties for a month at 4 degrees C in the dark.
“We hope that in a very near future these new methods of administration with ocular inserts, in this case for antioxidants, reach the market and represent significative progress in the efficiency of treatments for ocular tissues,” conclude the authors of the study.