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J.M. Houston, B. Adams, W.M. Petroll, H.D. Cavanagh, J.V. Jester; Corneal Haze after Excimer PTK in the Mouse Cornea Related to Stromal Cell Density and Myofibroblast Differentiation but Not Stromal Growth . Invest. Ophthalmol. Vis. Sci. 2003;44(13):892.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: The purpose of this study was to characterize the wound healing response after excimer laser PTK in the mouse cornea using in vivo and laser confocal microscopy. Methods: A total of 45 CD1 mice received 175 pulse, 10 hz excimer laser transepithelial photoablation within the central 2 mm of the right cornea. In 9 eyes, corneal wound healing was followed sequentially by in vivo confocal microscopy to measure epithelial thickness (ET), stromal thickness (ST) and stromal haze (Hz) 1 week pre-operatively and 1, 2, 4, 6, 8 and 12 weeks post-operatively. At the same time points, 5 mice were sacrificed for laser scanning confocal microscopy to measure cell density (CD) using syto 59 nuclear staining and myofibroblast differentiation using anti-α-smooth muscle actin staining (α-SMA). Results: Pre-operatively the mouse corneal ET, ST, Hz and CD respectively averaged 44.2 ± 3.6 µm, 73.2 ± 10.6 µm, 124 ± 39 U and 86,380 ± 13, 193 cells/mm3. The corneal stroma one week after PTK was 50% thinner averaging 38.0 ± 9.7 µm with little change in the ET (40.8 ± 4.1 µm). The stroma grew 8 µm to 46.9 ± 8.7 µm by week 2 but only an additional 3 µm by week 8. Greatest growth in ST occurred from week 8 to week 12 gaining approximately 11 µm to 60.2 ± 8.5 µm with no hyperplasia of the epithelium detected. By contrast Hz and CD were markedly elevated at 1 week averaging 1,574 ± 463 U and 124,837 ± 17,919 cells/mm3, and substantially decreased by week 2 averaging 1,138 ± 266 U and 106,196 ± 17,307 cells/mm3. While Hz and CD were relatively unchanged at week 4, both progressively declined from week 6 to 12 ending with a respective average of 438 ± 155 U and 86,888 ± 24,262 cell/mm3. Anti-α-SMA stained cells immediately underlying the epithelium at week 1 and 2 only. Conclusions: Overall, healing of PTK in the mouse cornea was similar to that previously established for PRK in the rabbit. Furthermore, changes in corneal Hz directly paralleled changes in cell density with peak haze associated with the presence of myofibroblasts.
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