Intracameral thrombin and the corneal endothelium

Topical thrombin-related corneal calcification

PURPOSE

To report a highly unusual case of corneal calcification after brief intraoperative use of topical thrombin.

METHODS

A 44-year-old man underwent sclerouvectomy for ciliochoroidal leiomyoma, during which 35 UNIH/mL lyophilized bovine thrombin mixed with 9 mL of diluent containing 1500 mmol/mL calcium chloride was used. From the first postoperative day, corneal and anterior lenticular capsule calcifications developed, and corneal involvement slightly enlarged thereafter.

RESULTS

A year later, 2 corneal punch biopsies confirmed calcification mainly in the Bowman layer. Topical treatment with 1.5% ethylenediaminetetraacetic acid significantly restored corneal clarity. Six months later, a standard extracapsular cataract extraction with intraocular lens placement improved visual acuity to 20/60.

CONCLUSION

This case suggests that topical thrombin drops with elevated calcium concentrations may cause acute corneal calcification in Bowman layer and on the anterior lens capsule.

Postoperative hypopyon after intravitreal bovine thrombin for macular hole surgery

PURPOSE

We used intravitreal autologous fibrinogen with bovine thrombin for the surgical closure of macular holes in 60 cases.

METHODS

Pars plana vitrectomy with separation of the posterior cortical vitreous was performed after air/fluid exchange. One to two drops each of autologous fibrinogen and bovine thrombin (20 to 80 U) were instilled in each patient.

RESULTS

Five (8%) of 60 patients developed a hypopyon without unusual pain on the first postoperative day. Inflammation responded to frequent topical corticosteroids within 48 to 72 hours.

CONCLUSION

Postvitrectomy hypopyon after the use of bovine thrombin may represent an immune reaction that must be differentiated from endophthalmitis. We recommend careful observation and frequent topical corticosteroids.

Thrombin induced cytoskeletal change in cultured bovine corneal endothelial cells mediated via protein kinase C pathway

We studied the participation of the protein kinase C pathway in thrombin-induced cytoskeletal alterations in confluent cultured bovine corneal endothelial (BCE) cells. Cultured BCE cells were exposed to alpha-thrombin (0.1-10 U/ml for 15-60 min) and the distribution of F-actin and vinculin plaques was examined using immunofluorescent staining and electron microscopy. Phorbol 12-myristate 13-acetate (PMA, 10 nM for 15 min), the broad spectrum protein kinase inhibitors staurosporine (10 nM) and H-7 (10 nM), and highly specific PKC inhibitor calphostin C (10 nM) were used to evaluate the role of PKC/phosphorylation in this phenomenon. HA-1004 (10 nM) was used as a negative control for these inhibitors. In a parallel experiment, PKC activity of cytosol and membrane of BCE cells was also evaluated. In control samples, F-actin was distributed mainly at the periphery of cells, where it formed dense peripheral bundles; vinculin plaques were also present at the cell boundary. Exposure of BCE cells to thrombin changed the distribution of F-actin and vinculin into a diffuse pattern; a similar alteration was also induced by incubation with PMA. These phenomena were blocked by incubation with H-7, staurosporine and calphostin C. Both cytosolic and membrane PKC activity was increased after 5 to 30 min exposure of alpha-thrombin and returned to the control level after 1 h. alpha-Thrombin induces alteration in the cytoskeleton of BCE cells, and this message is transduced at least in part by PKC dependent pathways. PKC/phosphorylation may thus play an important role in physiological processes that involve alterations of the cytoskeleton.

The effects of denatured sodium hyaluronate on the corneal endothelium in cats

In an in vivo cat model, wide-field specular microscopy and scanning electron microscopy were used to observe whether heat-denatured sodium hyaluronate causes cell damage to the corneal endothelium. The endothelial cell toxicities of various drugs, including 0.01% benzalkonium chloride, 0.2% chlorhexidine digluconate, and 0.5% lidocaine, mixed with intact or untreated sodium hyaluronate were also investigated. Neither heat-denatured nor intact or untreated sodium hyaluronate alone had any adverse effect on the corneal endothelium in cats, whereas 0.01% benzalkonium chloride and 0.2% chlorhexidine digluconate, mixed with sodium hyaluronate, caused substantial endothelial morphologic changes, which resulted in corneal edema. By comparison, 0.5% lidocaine with sodium hyaluronate was found to have minimal effect on the corneal endothelium in cats. These findings indicate that some chemical contaminant with sodium hyaluronate, not heat-denatured sodium hyaluronate, induces an immediate onset of pseudophakic bullous keratopathy.