Banayan N, Georgeon C, Grieve K, Ghoubay D, Baudouin F, Borderie V
Service d'ophtalmologie 5, Centre hospitalier national d'ophtalmologie des Quinze-Vingts, 28, rue de Charenton, 75012 Paris cedex 12, France.
Inserm UMR S 968, Sorbonne université, CHNO des 15-20, institut de la Vision, 75012 Paris, France.
J Fr Ophtalmol. 2018 Nov;41(9):e395-e406. doi: 10.1016/j.jfo.2018.09.003. Epub 2018 Oct 24.
The limbus is the anatomical and functional barrier between the corneal and conjunctival epithelia. It is characterized by the presence of the limbal stem cell niche, which allows corneal homeostasis to be maintained. Limbal stem cell deficiency is characterized by a dual process: insufficient regeneration of corneal epithelium, which cannot therefore assure its function of physiological support, associated with corneal invasion by conjunctival proliferation. Diagnosis is currently made via routine clinical examination, corneal impression cytology and in vivo confocal microscopy (IVCM). Slit lamp examination shows abnormal limbal anatomy, thin and irregular epithelium with late fluorescein staining, and superficial vascularization. With its high resolution, IVCM allows identification of limbal and corneal epithelial changes at a cellular level in en face views parallel to the corneal surface, but with a restricted viewing field of the corneal surface. It shows a poor transition between the corneal and conjunctival epithelia, associated with a loss of the normal corneal epithelial stratification, low basal cell and sub-basal nerve plexus densities, and subepithelial fibrosis. Spectral domain optical coherence tomography of the central cornea and limbus, with scans in variable orientations, allows a quick, global and non-invasive analysis of normal eyes and those with limbal stem cell deficiency. It shows a thin limbal epithelium, lacking normal thickening, featuring absence of stromal undulations and limbal crypts in cross-sections and sections parallel to the limbus, lack of visible limbal crypts in en face sections, loss of clear transition between the hyporeflective corneal epithelium and the hyperreflective conjunctival epithelium, and hyperreflective subepithelial fibrosis. The limbus is the anatomical and functional barrier between the corneal and conjunctival epithelia. It is characterized by the presence of the limbal stem cell niche, which allows corneal homeostasis to be maintained. Limbal stem cell deficiency (LSCD) is characterized by a dual process: insufficient regeneration of corneal epithelium, which cannot therefore assure its function of physiological support, associated with corneal invasion by conjunctival proliferation.
角膜缘是角膜上皮和结膜上皮之间的解剖学和功能屏障。其特征是存在角膜缘干细胞龛，该龛可维持角膜的内环境稳定。角膜缘干细胞缺乏表现为双重过程：角膜上皮再生不足，因此无法保证其生理支持功能，同时伴有结膜增生侵袭角膜。目前通过常规临床检查、角膜印片细胞学检查和活体共聚焦显微镜检查（IVCM）进行诊断。裂隙灯检查显示角膜缘解剖结构异常，上皮薄且不规则，荧光素染色延迟，以及浅层血管化。IVCM具有高分辨率，可在与角膜表面平行的正面视图中在细胞水平识别角膜缘和角膜上皮的变化，但角膜表面的观察视野有限。它显示角膜和结膜上皮之间的过渡不良，伴有正常角膜上皮分层丧失、基底细胞和基底神经丛密度降低以及上皮下纤维化。中央角膜和角膜缘的光谱域光学相干断层扫描，通过不同方向的扫描，可以对正常眼睛和角膜缘干细胞缺乏的眼睛进行快速、全面且无创的分析。它显示角膜缘上皮薄，缺乏正常增厚，在与角膜缘平行的横截面和切片中没有基质波动和角膜缘隐窝，在正面切片中没有可见的角膜缘隐窝，低反射性角膜上皮和高反射性结膜上皮之间缺乏清晰的过渡，以及高反射性上皮下纤维化。角膜缘是角膜上皮和结膜上皮之间的解剖学和功能屏障。其特征是存在角膜缘干细胞龛，该龛可维持角膜的内环境稳定。角膜缘干细胞缺乏（LSCD）表现为双重过程：角膜上皮再生不足，因此无法保证其生理支持功能，同时伴有结膜增生侵袭角膜。
