Transcorneal iontophoresis

Li et al. [196] studied the sites of ion delivery in the eye during iontophoresis. Using nuclear magnetic resonance imaging (MRI) and a probe ion (Mn2+), the study compared transscleral with transcorneal iontophoresis. The results have shown that transscleral iontophoresis delivered the ion into the vitreous, whereas transcorneal iontophoresis delivered the ion into the... 

Li, S.K., E.K. Jeong, and M.S. Hastings. 2004. Magnetic resonance imaging study of current and ion delivery into the eye during transscleral and transcorneal iontophoresis. Invest Ophthalmol Vis Sci 45 1224. 

Transcorneal iontophoresis of antibiotics for the treatment of corneal ulcers offers a potentially effective method of management. Numerous studies have demonstrated successful penetration of antibiotics into the anterior chamber after iontophoretic treatment, compared with topically eyedrop instillation of the drug [42,58,59,66,67], The efficacy of the treatment was investigated in rabbit eyes after intrastromal injection of Pseudomonas. Gentamicin, tobramycin, and ciprofloxacin iontophoresis resulted in significantly fewer bacterial colonies in the cornea compared with frequent eyedrops instillation [68-71],... 

Transcorneal Iontophoresis of Drugs into Rabbit Eyes... 

Despite these relatively successful results, transcorneal iontophoresis has never been studied in randomized, clinically controlled studies. The reason could be that the common topical drops treatment is relatively successful in treating most anterior ocular disorders with very few complications even though it requires frequent treatment. 

Transcorneal and transscleral iontophoresis, at the same conditions, can produce different toxicity levels due to the significant differences between cornea tissue and sclera. Any damage to the corneal surface immediately affects the vision and comfort of the patient, which is less pronounced when applied to the sclera. The clarity of the cornea is essential for interaction with light whereas the sclera is not relevant for light interaction. The cornea is an avascular and highly innervated tissue, unlike the sclera, and thus very sensitive to pain and hypoxia. On one hand, transcorneal iontophoresis endangers the front window of the eye, but on the other hand transscleral iontophoresis threatens the retina underneath the application site, which is essential for visual image formation. 

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