Abstract
Abstract: :
Purpose: Methylene blue (MB), a vital dye, is known to stain corneal and conjunctival epithelial cell without visible toxicity in vivo. To examine whether MB could be safely used in surgery for assisting of visualization of the internal limiting membrane or the epiretinal membrane, we evaluated the dose–related retinal toxicity of MB injected into the vitreous cavity of rabbit eyes. In addition, comparison with the effect of trypan blue (TB) was explored Methods: Pigmented Rabbits underwent gas–compression vitrectomy. 0.1 ml of MB (Sigma, USA) or TB (Sigma, USA) at a concentration of 0.03%, 0.06%, 0.1% or 0.2% was injected into the vitreous cavity in one eye of each rabbit. Preservative–free saline of equal volume was injected into other eyes as a control. All rabbits were examined and photographed before and after injection. Baseline and postinjection electroretinography (ERG) were performed. Four weeks after injections, rabbits were sacrified and eyes were enucleated for light and electron microscopic examination. Results: No ophthalmoscopic changes were seen in all eyes. There was no significant difference between ERGs recorded from control eyes and MB–injected eyes in any concentration group. Histological examination with light microscopy did not reveal any retinal abnormalities in the eyes injected with dye and saline. In the eyes injected with 0.1% and 0.2% of MB, some vacuolar changes were observed in the outer plexiform layer with electron microscopy. Almost the same changes were detected in the eyes injected with TB. Conclusions: This study demonstrated the lack of toxicity in the retina after prolonged presence of MB in the vitreous cavity following 0.1ml of 0.03% or 0.06% solution injection. But 0.1% and 0.2% solution of MB and TB showed a similar retinal toxicity. There is no difference in the toxicity evaluation between MB and TB.
Keywords: retina • ocular irritancy/toxicity testing • pathology: experimental