Comeal endothelium

Silhnan AJ, Weidner WJ. 1993. Low levels of inorganic mercury damage the comeal endothelium. Exper Eye Res 57 549-555. 

It constitutes the basement membrane of the comeal endothelium, separating it from the stroma. It is a strong, amorphous, and elastic membrane. It is about 10 pm in adulthood. It is synthesized by the endothelial cells from the fourth month of embryonic life. The Descemet s membrane has got two distinct sides ... 

The comeal endothelium constituted of one unique layer of cells, 5-10 pm thick... 

Figure 35-3 Heavy pigment deposits on comeal endothelium, caused by chlorpromazine administration. (Courtesy Jerome Thaler, O.D.)...

A 50-year-old woman with schizophrenia had a 1-year history of gradual deterioration of vision in both eyes. For several years she had been taking chlorpromazine 300 mg/day, trifluoperazine 10 mg/day, and trihexjrphe-nidyl 4 mg/day. Slit lamp examination showed fine, discrete, brown retractile deposits on the comeal endothelium in both eyes, and characteristic bilateral stellate cataracts with dense, dust-like brown-yellow granular deposits were noted along the suture lines in the anterior pole of the lens and obscured the visual axis. 

Figure 4 Human comeal endothelium following three-hour perfusion with lactated Ringer s solution (A) scanning electron micrograph (2100x), (B) transmission electron micrograph (9100x). Source-. Courtesy of H. Edelhauser.

Kwon OH, Kikuchi A, Yamato M et al (2003) Accelerated cell sheet recovery by co-grafting of PEG with PIPAAm onto porous cell culture membranes. Biomaterials 24 1223-1232 Lai JY, Chen KH, Hsu WM et al (2006) Bioengineered human comeal endothelium for transplantation. Arch Ophthalmol 124 1441-1448... 

Liang Y, Liu WS et al (2011) An in situ formed biodegradable hydrogel for reconstruction of the comeal endothelium. Colloids Surf B 82 1-7... 

Cerilpyridiniutii chloride is the 1-hexadecylpyridinium chloride (USP/NF-. Eur.Ph.-, BP-, and Martindate-compliant). Lin et al. (33) compared the primaiy ocular and dermal irritations of several quaternary ammonium compounds. They concluded that the irritancy of these compounds is likely to be related to their solubility in addition to their cationic characteristics. Only celylpyridinium chloride is very soluble in both lipids and w er. It appears that not all of the quaternary ammonium compounds studied are irritant, but celylpyridinium chloride was severely irritating to the skin of the test animal. In a recent work. Green et al. (34) confirmed that ophthalmic medications containing celylpyridinium chloride are potentially hazardous to the comeal endothelium. 

A 66-year-old Chinese man developed comeal endothelial decompensation after intraocular lens repositioning using intra-cameral adrenaline, attributed to prolonged, direct exposure of the comeal endothelium to relatively high concentrations of adrenaline [69 ]. The authors recommended that intracameral epinephrine should not be used for intraoperative mydriasis in procedures in which high concentrations of adrenaline are likely to result. 

Descetnel s membrane is acellular elastic tissue that acts as a basement membrane for the comeal endothelium. 

Sensory systems An in vitro study assessed the cytotoxic effect of GCV on cultured hmnan comeal endothelial (HCE) cells, in view of the possibility of using intracameral GCV injections in CMV endotheliitis and retinitis. GCV was demonstrated to have dose-dependent cytotoxic effects [31 ]. There was a significant decrease in HCE cell viability at GCV concentrations of 5 mg/mL, which may therefore be associated with a higher risk of damage to the comeal endothelium. This effect was not found with concentrations of 0.5mg/mL. 

Mcgowan, S,L Edelhauser, H.F, Pfister, R,R, Whikehart, D,R, Stem cell markers in the human posterior limbus and comeal endothelium ok unwounded and wounded corneas. Mol Vis 13,1984-2000 (2007)... 

FIGURE 38.2 Structure of the cornea. Left Representative histology of a rabbit corneal section. Scale bar is 40 pm. Right Transmission electron microscopy of a rabbit eye, demonstrating the ultrastructure of different corneal layers. Scale bar is 4 pm. Labels ce comeal epithelium b basal epithelial cell bll Bowman s-like layer as anterior stroma k keratocytes ps posterior stroma dm Descemet s membrane endo comeal endothelium. Unpublished data. 

The cornea is composed of five histologically distinct layers with different regenerative capacity corneal epithelium. Bowman s or Bowman s-like layer, stroma, Descemet s membrane (DM), and comeal endothelium (Figure 38.3). The comeal epithelium is a stratified epithelium with 5-7 cell layers that provides a dynamic... 

Damages to the comeal limbus and the comeal endothelium have emeiged as pathophysiologies that may be critically involved in MGK onset, progression, or both. Both pathologies are consistent with clinical observations in human MGK corneas and are spatio-temporally expressed in such a way to contribute to the long-term comeal HD injury (Baradaran-Rafii et al., 2010 Jafarinasab et al., 2010). 

The potential involvement of endothelial toxicity in the late HD injury is intriguing for several reasons. First, it provides a mechanism to explicate the dose dependence of MGK onset, based on the permeation of sufficient doses of HD through the cornea to cause injury to the comeal endothelium. Second, it proposes that the clinically biphasic injury progression observed during the acute phase is an epiphenomenon arising from the differential healing capacities of the comeal epithelium... 

---