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Sarah Peterson, Satish Herekar, Marc D Friedman, Evan A Sherr, David Muller; Pentacam Densiometry Method for Analysis of Cross-linking in Whole Porcine Globes. Invest. Ophthalmol. Vis. Sci. 2014;55(13):3720.
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© ARVO (1962-2015); The Authors (2016-present)
To evaluate the use of Pentacam densitometry maps in conjunction with a new laboratory protocol as a method to measure differences in UVA-RF crosslinking induced changes in whole globe porcine eyes.
18 fresh whole globe porcine eyes were obtained <24 hours postmortem in saline on ice from Sioux-Preme (Sioux City, IA). Epithelium was removed with a dull blade, and globes were soaked in Blood Bank Buffered Saline (Fisher Scientific, Agawam MA) for >20 minutes at 37°C. Globes were mounted on a holder and an intraocular pressure of 30mmHg was applied to the globe through a cannula. Drops of 0.1% Riboflavin with 0.25%HPMC were applied to the corneas every 2 minutes for a total of 15 minutes at 37°C. The corneas were aligned to a Pentacam HR (Oculus Optikgeräte GmbH) outfitted with a 475nm (±25nm) notch filter to eliminate fluorescence saturation. Three pre-illumination images were acquired for each cornea. Avedro’s KXL-II (Avedro, Inc. Waltham MA) was used to illuminate a 4mm central circular spot on the cornea with a UVA(365nm) irradiance of 30mw/cm2 for a total dosage of 10, 15 or 20J/cm2. The 0.1% Riboflavin formulation was applied every 4 minutes during UVA exposure, following which, three post-illumination images were acquired for each cornea. Density ratios were determined by comparing a 2mm central treatment zone to the 6mm non treatment zone. The pre-illumination density ratios were compared to the post-illumination density ratios, and graphed vs. Avedro KXL-II UVA dose.
Corneal densitometry changes pre to post UVA exposure clearly show the 4mm diameter pattern exposed. The corneal density increased linearly with increasing UVA dose (R2 = 0.98).
Pentacam densiometry difference maps produce a linear relationship between UVA dosage and pre-illumination/post-illumination density ratios and may be a useful method in quantifying corneal cross-linking.
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