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Jeffrey Z Tsao, Landon K Grange, C Andres Benatti, Hideki Fukuoka, Natalie A Afshari; Objectively measuring optical blurring in amniotic membranes and the effects of collagen cross-linking. Invest. Ophthalmol. Vis. Sci. 2017;58(8):4861.
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© ARVO (1962-2015); The Authors (2016-present)
Amniotic membranes are used in corneal and conjunctival surgeries to promote wound healing among other beneficial effects. We aimed to study the clarity of amniotic membranes as well as to examine the effects cross-linking on optical quality.
Five different amniotic membranes types (three cryopreserved and two dehydrated) and Collagen Shield as control were analyzed with two samples each (n = 15), three each for the dehydrated samples. Optical blurring quantified as “blur index” was calculated via image analysis of a photo taken of the sample over a laptop liquid crystal display, using the standard deviation ratio of gray values seen from the membrane over the petri dish they rested upon. A “transparency ratio” estimated transmittance by comparing the maximum gray values of sample versus petri dish. For cryopreserved membrane types, we also examined the impact of time after package opening on transparency (fresh vs 1 week old). Finally, using riboflavin and UV light we cross-linked a sample of each type and measured the optical effect.
Blur indices among all membranes ranged from 0.255% to 24.6%, with smaller values signifying minimal blurring for all membrane types.Transparency ratios ranged between 0.90 and 1.08, with greater values signifying more brightness. BI and TR had an inverse correlation (r = –0.923, 95% CI 0.847–0.962).Cross-linking had a range of effects on BI values, from a 36% reduction to a 41% increase, and a smaller range of effects on TR values, from a 5% reduction to 3% increase.
This quick method helps objectively assess the amount of blurring from amniotic membranes. The blur index measurement could potentially be useful in predicting what a patient may experience visually, but further study would be needed to correlate with effects on visual acuity. Collagen cross-linking did not have a predictable or statistically significant effect on BI or TR.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
Screenshot of image analysis with gray value graphs comparing an amniotic membrane to petri dish.
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