Purpose: To investigate the safety of the thrombolytic agent, tenecteplase to the outer retina in pig eyes.Methods: Tenecteplase (50 mu g) was injected into the subretinal space in one eye while the fellow eye received balanced salt solution. At 24 h, 1 week and 9 weeks the eyes were examined by indirect ophthalmoscopy and photographed. Animals were killed at 9 weeks, eyes enucleated and processed for light and transmission electron microscopy. Three locations within the area of the injection bleb were analysed.Results: Retinal pigment epithelial defects, which appeared to be iatrogenic and confined to the injection site, were seen in most of the treated and control eyes. There was no significant difference in the degree of retinal damage between the two groups of eyes at the three sites examined (P > 0.05).Conclusion: Fifty micrograms of tenecteplase appears to be a safe dose with no evidence of toxicity to the outer retina and may have a potential role in the treatment of submacular haemorrhage.