title: Intravitreal tenecteplase (metalyse) for acute management of retinal vein occlusions.
abstract: OBJECTIVE
  To determine the ability of an intravitreal injection of tenecteplase (TNK) to penetrate an intraretinal venous thrombus and its effectiveness in thrombolysis in a porcine model of branch retinal vein occlusion (BRVO).
  
  
  METHODS
  Six pigs (group 1) were anesthetized, and a BRVO was induced photothrombotically in the left eye; immediately afterward, fluorescence-conjugated TNK (100 μg) was injected into both eyes, with enucleation at 24 hours. Retinal penetration was assessed on frozen sections by epifluorescence microscopy. A further six pigs (group 2) were anesthetized; BRVO was induced in both eyes, and TNK was injected into the vitreous in the left eye. Both eyes were harvested a week later. The area of the lasered site and an area away from the burn were dissected and processed in epoxy resin and stained for light or transmission electron microscopy. The percentage blockage, clot volume, cytostructure, and extent of thrombolysis by TNK were assessed.
  
  
  RESULTS
  TNK penetrated the veins in both eyes of group 1 pigs, with more intense staining in the eyes with the occlusion. In group 2 eyes, thrombolysis was significant in the eyes injected with TNK (P = 0.03); blockage was seen in all six untreated eyes and one treated eye. Clot volume was significantly higher in untreated eyes (P = 0.028). Percentage blockage varied from 8.5% to 83.9%. Damage by TNK to the neural retina was not seen. There was no significant difference in cytostructure between treated and untreated eyes (P = 0.357).
  
  
  CONCLUSIONS
  TNK was able to penetrate the retinal veins with and without an occlusion and effect lysis of BRVO, and did not cause damage to the retinal tissue. Intravitreal TNK may be useful as an acute treatment for RVOs of recent onset.
authors.affiliation: Lions Eye Institute, Centre for Ophthalmology and Visual Science, University of Western Australia, Perth, Australia. ianmcallister@lei.org.au.
authors.forename: Ian L
authors.initials: IL
authors.lastname: McAllister
authors.forename: Sarojini
authors.initials: S
authors.lastname: Vijayasekaran
authors.forename: Dao-Yi
authors.initials: DY
authors.lastname: Yu
mesh_terms: D000208:Acute Disease; D000818:Animals; D004195:Disease Models, Animal; D005343:Fibrinolytic Agents / Q000008:administration & dosage* / Q000493:pharmacokinetics; D058449:Intravitreal Injections; D012169:Retinal Vein / Q000378:metabolism; D012170:Retinal Vein Occlusion / Q000188:drug therapy* / Q000378:metabolism; D013552:Swine; D000077785:Tenecteplase; D015912:Thrombolytic Therapy / Q000379:methods*; D010959:Tissue Plasminogen Activator / Q000008:administration & dosage* / Q000493:pharmacokinetics
chemical_list: D005343:Fibrinolytic Agents; D010959:Tissue Plasminogen Activator; D000077785:Tenecteplase
keywords: BRVO; TNK; vitreoretinal surgery