GFAP and diabetic retinopathy: This difference of expression of GFAP which is a pan glial retinal marker between the two diseases shows that the extent of glial damage is more in diabetic retinopathy, compared to MacTel2 in which the expression of Müller cell specific markers e.g. GS (glutamine synthetase) and CRALBP (cellular retinaldehyde binding protein) are specifically reduced.