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Samantha Bradford, Eric R Mikula, Yilu Xie, Donald Brown, Tibor Juhasz, James V Jester; Enhanced Transepithelial Riboflavin Delivery Using Femtosecond Laser Machined Epithelial Microchannels. Invest. Ophthalmol. Vis. Sci. 2020;61(7):2580.
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© ARVO (1962-2015); The Authors (2016-present)
Ultraviolet light corneal collagen crosslinking (UVA-CXL) via photoactivation of riboflavin (Rf) is an effective treatment for Keratoconus that is also being developed as a refractive corneal procedure. A major drawback of UVA-CXL is the need to remove the corneal epithelium to achieve adequate stromal Rf concentrations for CXL, leading to patient discomfort, delayed visual recovery, and risk of infection. Transepithelial (TE) CXL, even using chemical disruption of the corneal epithelial barrier, has been shown to have limited success in both increasing stromal Rf concentration and decreasing patient pain and delayed visual recovery. This study describes a femtosecond laser (FS) approach to machine corneal epithelial microchannels (MC) for enhanced stromal Rf penetration. This technique when combined with nonlinear optical CXL (NLO CXL) results in no damage to the corneal epithelium.
Using a 1030nm FS laser with 5-10μJ pulse energy, the corneal epithelium of ex vivo rabbit eyes were machined to create 2μm diameter by 25μm long MC at a density of 100-400 MC/mm2. Stromal Rf penetration through the MC was then determined by applying 1% Rf in PBS for 30 minutes followed by removal of the cornea and extraction from the central stromal button. Stromal Rf concentrations were then compared to those obtained using standard epithelial debridement or TE using 0.01% BAK to disrupt the epithelial barrier.
MC formed using 5μJ/pulse at a density of 400 MC/mm2 achieved a stromal Rf concentration that was 50% of that achieved by epithelial debridement and imbibing with 1% Rf. Stromal Rf levels were also equal to that of debrided corneas soaked with 0.5% Rf, and significantly greater than debrided corneas soaked with 0.1% RF (3 fold higher) or TE corneas treated with 1% Rf in BAK (2 fold higher). Organ culture of NLO CXL treated corneas showed a normal corneal epithelium following FS machining while TE BAK treated corneas showed extensive epithelial and stromal damage at 24 hours post treatment.
FS epithelial machining can be used to enhance stromal penetration of Rf for corneal CXL. When paired with NLO CXL, this method minimizes epithelial and stromal damage, and should lead to greater patient comfort, more rapid visual recovery and no risk of infection.
This is a 2020 ARVO Annual Meeting abstract.
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