Alternative photosensitizer penetration depth evaluation in ex vivo human eyes for photodynamic antimicrobial therapy
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James M Lai1, Katherine Krishna1, Brandon Chou1
1Ophthalmic Biophysics Center, Department of Ophthalmology, University of Miami Miller School of Medicine, Miami, FL, USA.
Purpose:
Fungal keratitis has a poor prognosis given deep penetration into the corneal stroma. While Rose Bengal photodynamic antimicrobial therapy (RB-PDAT) is a promising adjunct treatment for refractory cases, poor penetration limits its effectiveness. This study explores the penetration depth of alternative photosensitizers to address this issue.
Methods:
Thirty-five human corneas were soaked for 30 minutes in 0.0075% solution of Rose Bengal disodium (n = 5), Rose Bengal lactone (n = 5), Erythrosin B disodium (n = 5), Erythrosin B lactone (n = 5), Eosin Y disodium (n = 5), Methylene blue (n = 5), or NaCl (control, n = 5). Confocal microscopy was used to assess penetration depth.
Results:
All photosensitizers penetrated greater into the cornea as compared to control. There was no significant difference in penetration between Rose Bengal lactone and Rose Bengal disodium (RB lactone: 106 ± 11 µm vs RB disodium: 99 ± 13 µm, p > 0.05). The penetration depths of the alternative photosensitizers was significantly greater than either Rose Bengal formulation (Erythrosin Blactone: 192 ± 31 µm, Erythrosin B disodium: 163 ± 13 µm, Eosin Y disodium: 249 ± 31 µm, Methylene Blue: 355 ± 151 µm).
Conclusions:
Alternative photosensitizers exhibit superior penetration compared to Rose Bengal. However, antimicrobial efficacy and corneal safety require more robust evaluation before clinical use.
