Corneal haze development after PRK is regulated by volume of stromal tissue removal
Corneal haze development after PRK is regulated by volume of stromal tissue removal
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DOI：
10.1097/00003226-199811000-00011
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发表时间：
1998-11-01
期刊：
影响因子：
2.8
通讯作者：
Jester, JV
中科院分区：
文献类型：
--
作者：
Moller-Pedersen, T;Cavanagh, HD;Jester, JV
目的.确定准分子激光经上皮光消融术是否可以减少手动上皮清创术后观察到的初始角膜细胞损失。第二，建立角膜上皮细胞的初始厚度和基质丢失与角膜haze发生的关系。方法.五只兔子接受了5毫米直径的单眼上皮清创手动刮。另外5只兔子接受了5 mm直径的准分子激光经上皮光消融，预设（预期）深度为60 μ m，以确保完全去除上皮，并在所有角膜中进行浅层基质角膜切除术。在3个月期间的不同时间，通过体内聚焦共焦显微镜（CMTF）评估动物，其产生角膜的定量图像强度深度分布，其提供（i）角膜细胞损失的深度、（ii）上皮和基质厚度和（iii）来自前角膜的反向散射光的测量值作为角膜混浊的客观估计。结果手动上皮清创术与前基质角膜细胞最初损失至108 +/- 14 μ m的深度相关，随后是迁移性角膜细胞的再增殖。这些细胞显示出增加的反射率，在3周时产生相当于临床混浊等级1-2（1，442 +/-630 U）的显著的光反向散射。此外，在没有可检测到的炎症的情况下发生再增殖，并且与正常角膜细胞形态和反射率的快速恢复相关。除了14-44 μ m的浅层基质角膜切除术外，经上皮光消融还诱导了所有角膜的完全上皮清创。与手动清创相比，光消融诱导的前基质中的初始角膜细胞损失（69 +/- 19 μ m）减少了36%（p < 0.01），但与强烈的伴随炎症相关。与手动清创角膜相比，光消融角膜显示出显著更多的光反向散射（p < 0.01），在3周时增加了3倍（4，397 +/-1，367 U），在3个月时增加了6倍（1，483 +/-1，172与234 +/- 91 U相比）。后向散射光或混浊随基质角膜切除术深度的增加而成比例增加（r = 0.95，p < 0.001），但与诱导的角膜细胞死亡深度无关。光消融角膜后向散射增加似乎与（i）角膜细胞再生反应更明显，迁移成纤维细胞密度和反射率更高，以及（ii）再生后肌成纤维细胞转化相关。结论：准分子激光经上皮光消融术诱导的角膜细胞损失显著低于手动上皮清创术;然而，光消融术后出现更强烈的炎症反应和更大程度的光反向散射（haze）增加，这与角膜细胞活化和肌成纤维细胞转化增加有关。最重要的是，角膜伤口修复的程度以及角膜混浊的发展和持续时间随着基质光消融深度的增加而成比例地增加（即，基质组织去除的体积），但与初始角膜细胞损失的深度无关。
Purpose. To determine whether excimer laser transepithelial photoablation can reduce the initial keratocyte loss seen after manual epithelial debridement. Second, to establish the relationship between initial depth of keratocyte and stromal loss and the subsequent development of corneal haze. Methods. Five rabbits received a 5-mm diameter monocular epithelial debridement by manual scraping. An additional five rabbits received a 5-mm diameter excimer laser transepithelial photoablation to a preset (intended) depth of 60 mu m to ensure complete epithelial removal and to generate a superficial stromal keratectomy in all corneas. At various times during a 3-month period, animals were evaluated by in vivo confocal microscopy through focusing (CMTF), which generates a quantitative image intensity depth profile of the cornea that provides measurements of (i) depth of keratocyte loss, (ii) epithelial and stromal thickness, and (iii) backscattered light from the anterior cornea as an objective estimate of corneal haze. Results. Manual epithelial debridement was associated with an initial loss of anterior stromal keratocytes to a depth of 108 +/- 14 mu m that was followed by repopulation with migratory keratocytes. These cells showed increased reflectivity producing significant backscattering of light equivalent to clinical haze grade 1-2 (1,442 +/- 630 U) at 3 weeks. Furthermore, repopulation occurred without detectable inflammation and was associated with a rapid restoration of normal keratocyte morphology and reflectivity. Transepithelial photoablation induced complete epithelial debridement in all corneas in addition to a superficial stromal keratectomy of 14-44 mu m Photoablation induced 36% less initial keratocyte loss (69 +/- 19 mu m) in the anterior stroma than manual debridement (p < 0.01) but was associated with intense concomitant inflammation. Photoablated corneas showed significantly more light backscattering (p < 0.01) compared with manually debrided corneas with a threefold increase at 3 weeks (4,397 +/- 1,367 U) and a sixfold increase at 3 months (1,483 +/- 1,172 compared with 234 +/- 91 U). Backscattering of light or haze increased proportionally with increasing stromal keratectomy depth (r = 0.95, p < 0.001) but was unrelated to depth of induced keratocyte death. The increased backscatter in photoablated corneas appeared related to (i) a more pronounced keratocyte repopulation response with a higher density and reflectivity of migratory fibroblasts and (ii) myofibroblast transformation after repopulation. Conclusions, Excimer laser transepithelial photoablation induced significantly less keratocyte loss than manual epithelial debridement; however, photoablation was followed by a more intense inflammatory response and a greater increase in backscattering of light (haze) that was associated with increased keratocyte activation and myofibroblast transformation. Most important, the magnitude of corneal wound repair and the development and duration of corneal haze increased proportionally with increasing stromal photoablation depth (i.e., the volume of stromal tissue removal) but were unrelated to depth of initial keratocyte loss.