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Holly Butler Hindman, Margaret DeMagistris, Christine Callan, Thurma McDaniel, Krystel R Huxlin; Differential Effects of Topical Mitomycin C and Steroid on Wound Healing and Optics after Photorefractive Keratectomy in Cats. Invest. Ophthalmol. Vis. Sci. 2016;57(12):1285.
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© ARVO (1962-2015); The Authors (2016-present)
To assess the differential effects of topically applied agents on myofibroblast transformation and optical outcomes following photorefractive keratectomy (PRK) in a cat model.
26 eyes of 13 cats underwent -10 D myopic PRK. Cats were then assigned to 1 of 3 treatment groups: control, Mitomycin C (MMC – 0.02% for 2 mins) and topical steroid (BID for 2 wks). Corneal thickness and reflectivity were measured using optical coherence tomography (OCT) and wavefront aberrations were quantified using a Hartmann-Shack aberrometer. Cats were sacrificed for histology at 2, 4, and 12 wks post-PRK. Corneas were excised, fixed and stained immunohistochemically for alpha-smooth muscle actin (α-SMA).
2 weeks after PRK, significant differences were noted with respect to stromal (KW=9.576, P<0.01) and epithelial thickness changes (KS=7917, P<0.05) between groups. Control and steroid-treated eyes had increased stromal thickness and decreased epithelial thickness relative to MMC-treated eyes. MMC treatment also resulted in a thinner band of α-SMA staining and lower stromal reflectivity 2 wks post-operatively than in control and steroid-treated eyes. By 4 wks post-PRK, there was no detectable α-SMA in MMC-treated eyes, whereas control and steroid-treated eyes continued to express it. By 12 wks post-PRK, stromal reflectivity in MMC-treated eyes (but not control or steroid-treated eyes) returned back to baseline. By 12 wks post-PRK, there were also significant differences in the amount of defocus change induced by PRK between the 3 groups (KW=9.269, P<0.0005, D=7.75, P< 0.01), with MMC eyes exhibiting the greatest treatment effect (defocus change: -5.45 ± 0.17µm relative to baseline). Steroid-treated eyes showed moderate regression (defocus change: -3.30 ± 0.35 µm), while control eyes had the most severe regression (defocus change: -2.04±0.36 µm). However, by 12 wks, no significant differences in induced higher order root mean square (HORMS) existed between groups (control: +0.39 ± 0.34 µm, steroid: +0.60 ± 0.15 µm, MMC: +0.91 ± 0.17 µm; KW = 2.35, P=0.34).
Relative to steroid-treated and control eyes, MMC treatment was associated with more favorable wound healing responses and optical outcomes after PRK. This included a decrease in the amount and length of α-SMA expression, greater epithelial stability, and less myopic regression.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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