Fig. 3

Morphologic characteristics of foveal immaturity observed by use of spectral-domain optical coherence tomography (SD-OCT). The first line displays the three grades of inner retinal layers’ extrusion from the foveal center: grade 1, incomplete INL extrusion, and grade 0; absent of INL extrusion. The second line shows the three grades of foveal shape maturity: grade 0, absence of foveal pit, grade 1 shallow pit, and grade 2 normal deep foveal pit. The last line shows the types of outer segment layers in ROP patients: All of the external limiting membrane (ELM), Ellipsoid zone (EZ) and RPE are detectable, only 2 of them are visible and only 1 hyper-reflective layer was visible