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Kaitlin T Wozniak, Sam C Butler, Margaret DeMagistris, Christine Callan, Wayne Knox, Jonathan D Ellis, Krystel R Huxlin; Short- and long-term impact of Laser-Induced Refractive Index Change (LIRIC) on corneal nerve distribution in rabbits. Invest. Ophthalmol. Vis. Sci. 2019;60(9):5076. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Disruption of corneal innervation is a significant side-effect of laser refractive surgeries such as LASIK. Our team has developed Intra-tissue Refractive Index Shaping (IRIS) into a non-ablative, laser refractive correction procedure named Laser-Induced Refractive Index Change (LIRIC), which was recently performed in humans for the first time. Here, we asked whether LIRIC damages or otherwise impacts the distribution of corneal nerves in a rabbit model.
LIRIC was performed in 10 eyes from 8 Dutch Belted rabbits using a 405nm Ti:Sapphire laser under topical and surgical anesthesia. Corneas were applanated and a high NA objective was used to create a 4.5mm diameter Fresnel lens with a +2.5D spherical correction in the mid-stroma. To separate laser from applanation effects, 6 Sham eyes received no laser treatment, but were applanated for the same duration. Four hours after LIRIC/Sham, 4 rabbits were sacrificed; 5 LIRIC and 3 Sham eyes were placed in fixative and processed for histology. Three months after LIRIC/Sham, 4 more rabbits were processed identically. Two rabbit eyes were analyzed as untreated controls. Frozen corneal sections were immunoreacted with βIII tubulin (TUJ1) antibodies, followed by secondary antibodies tagged with Alexa-555, and counter-stained with DAPI. Corneal sections were traced and analyzed with Neurolucida to measure nerve lengths and densities.
Immediately after LIRIC/Sham, compared to controls, both LIRIC and Sham eyes had lower epithelial Tuj1-positive nerve densities (mean±SD; LIRIC: 2.9±2.3 mm/mm2; Sham 0.6±0.01 mm/mm2; control: 7.7±1.9 mm/mm2) and lower sub-basal nerve lengths (LIRIC: 0.3±0.3 mm; Sham: 0.02±0.01 mm; control: 0.8±0.2 mm). In contrast, stromal nerve densities appeared unaffected (LIRIC: 0.4±0.1 mm/mm2; Sham: 0.3±0.06 mm/mm2; control: 0.5±0.2 mm/mm2). Three months after treatment, nerve distributions had returned to normal (control levels) in all 3 corneal layers.
LIRIC and Sham eyes exhibited depressed TUJ1 staining in the epithelium and sub-basal layer immediately after treatment, suggesting that the effect was caused by applanation rather than LIRIC. Because this effect had disappeared 3 months later, we concluded that LIRIC does not negatively impact corneal nerve distribution and may avoid long-term, post-operative side-effects such as pain, discomfort, and dry eye.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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