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S.E. Wilson, M.V. Netto, R.R. Mohan; Myofibroblast Generation in the Anterior Stroma Is Triggered by Surface Irregularity . Invest. Ophthalmol. Vis. Sci. 2005;46(13):2159.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To determine the relationship between the level of stromal surface irregularity and myofibroblast generation. Methods: A fine mesh screen was used to mask excimer laser ablation using a refractive ablation of –4.5 diopters (D) by placing the screen for varying percentages of pulses at the end of the ablation in 35 New Zealand rabbits, divided into five different groups: –4.5 D PRK with no screening (group I), –4.5 D PRK with screening of 10% of pulses (group II), –4.5 D PRK with screening of 30% of pulses (group III), –4.5 D PRK with screening of 50% of pulses (group IV) and –4.5 D PRK with screening of 50% of pulses followed by smoothing phototherapeutic keratectomy using either hyaluronic acid or 1% methylcellulose as masking agents (group V). Slit lamp analysis and haze grading was performed in all five groups. Rabbits were sacrificed at 4 weeks after treatment and corneas underwent immunohistological staining for myofibroblast marker alpha–smooth muscle actin (SMA). Results:Slit–lamp examination revealed significant haze formation in corneas in groups III and IV, less in group II, and little haze in groups I or V. Analysis of SMA staining at 4 weeks after surgery showed the lowest myofibroblast formation in groups I (3.0 ± 5.1 cells/400x field) and V (3.2 ± 5.7), with progressively more in groups II (7.1 ± 6.5 ), III (11.8 ± 7.2) and IV (19.5 ± 10.0). Group I was significantly different from groups II, III, and IV, and groups II and III were significantly different from group IV (p < 0.05). Groups I and V were not significantly different. Conclusions: Objective and subjective analysis demonstrated a correlation between the level of stromal surface irregularity and the level of corneal haze formation after surface ablation. We hypothesize that surface irregularity leads to abnormal basement membrane regeneration and, therefore, greater TGF beta and PDGF penetration into the stroma from the epithelium, associated with trans–differentiation of keratocytes to myofibroblasts. Alternatively, greater surface area of contact between epithelium and the underlying stroma may be the key factor associated with greater TGF beta and PDGF access to the stroma and resulting myofibroblast generation. EY10056
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