[Evaluation of trypan blue toxicity in idiopathic epiretinal membrane surgery with macular function test using multifocal electroretinography: seven prospective case studies].

Introduction: Idiopathic epiretinal membranes are considered the consequence of glial proliferation through a defect of the internal limiting membrane and can induce a functional macular syndrome associating mainly metamorphopsia and visual acuteness. Visual disturbance is not bound to the area and the degree of transparency of the membrane, but to distortion of external layers of the retina. Multifocal electroretinography (ERGm) can assess the macular area and retina extending 20 degrees. We used this tool to study macular function pre- and post-operatively with seven patients presenting idiopathic epiretinal membrane.

Patient And Method: All patients had successful vitrectomy, with 0.2 ml of 0.15% trypan blue (TB) staining to facilitate peeling. This stain is not toxic for the pigment epithelium but it becomes so for photoreceptors at doses exceeding 0.2%. We tried to estimate the echo of TB 0.15% on photoreceptors through this exam. An ERGm was done 1 week before the operation as well as 1 month and 4 months after on 14 eyes of seven patients with ERMs.

Results: Results show a pre-operative decrease in the electrical retinal response densities in the foveal, perifoveal and parafoveal areas. One month after operation, no significant difference was found compared to pre-operative results. However, at 4 months, an improvement of the retinal response density was observed. Retinal response densities in the macular area increased progressively after ERM surgery.

Conclusion: The 0.15% TB facilitated ERM peeling and does not seem to present any retinal toxicity.