Background: In adult rats we study the short- and long-term effects of focal blue light-emitting diode (LED)-induced phototoxicity (LIP) on retinal thickness and Iba-1+ activation.
Methods: The left eyes of previously dark-adapted Sprague Dawley (SD) rats were photoexposed to a blue LED (20 s, 200 lux). In vivo longitudinal monitoring of retinal thickness, fundus images, and optical retinal sections was performed from 1 to 30 days (d) after LIP with SD-OCT. Ex vivo, we analysed the population of S-cone and Iba-1+ cells within a predetermined fixed-size circular area (PCA) centred on the lesion.
Results: LIP resulted in a circular focal lesion readily identifiable in vivo by fundus examination, which showed within the PCAs a progressive thinning of the outer retinal layer, and a diminution of the S-cone population to 19% by 30 d. In parallel to S-cone loss, activated Iba-1+ cells delineated the lesioned area and acquired an ameboid morphology with peak expression at 3 d after LIP. Iba-1+ cells adopted a more relaxed-branched morphology at 7 d and by 14-30 d their morphology was fully branched.
Conclusion: LIP caused a progressive reduction of the outer retina with loss of S cones and a parallel dynamic activation of microglial cells in the lesioned area.
Keywords: LED-induced phototoxicity; adult albino rat; cone photoreceptor; microglia activation.