<prompt> Blood retinal barrier is formed byMuller cellsAmacrine cellsHorizontal cellsOuter Plexiform layer  <response>: Ans. d Outer Plexiform layerRef: Retina by Ryan 6e, p. 657; Khuranas Anatomy 2e, p. 151Blood retinal barrier at 2 levels Inner - Non-fenestrated capillaries of the retinal vessels superficial capillary network in NFL and deep capillary network between INL and OPL Outer - tight junctions of RPE 