FLORetina 2025: A second Müller glial cell type in the human fovea

Christine A. Curcio, PhD, FARVO, presented highlights from her research, focusing on Müller glia organization in the human fovea and what prematurity may reveal about foveal development and plasticity, at the FLORetina 2025–International Congress on OCT and OCT Angiography (ICOOR), held from 4 to 7 December in Florence, Italy.¹ Her presentation centered on data from a published study of a single adult fovea from an organ donor who died at age 28 and had been born at 28 weeks’ gestation. Curcio is with the UAB Heersink School of Medicine in Birmingham, Alabama, USA.

The study was enabled by volume electron microscopy, which Curcio described as “like OCT at the nanometer scale.” This approach allowed reconstruction of entire Müller cells at 50-nm resolution—critical for studying Müller glia, which are large, complex cells spanning much of the retinal thickness. Previous techniques had provided only partial views.

Two principal findings emerged. First, the fovea itself was small, with a small foveal pit and foveal avascular zone. The underdeveloped pit contained abundant Müller glia, consistent with known mechanisms of foveal development. As Curcio explained, ganglion cells normally migrate centrifugally over a prolonged developmental period, and “that can be interrupted by premature birth.” The team interpreted the small pit and retained Müller glia as an expected consequence of prematurity, reflecting what is now often termed macular arrested development.

The second finding was unexpected: the presence of a second Müller glial cell type in the foveal center. In addition to classic Müller glia spanning from the inner limiting membrane (ILM) to the external limiting membrane (ELM), the investigators identified cells with Müller-like ultrastructural features that extended only from the ILM to the outer plexiform layer (OPL). These cells wrapped tightly around foveal circuitry, from cone pedicles through bipolar and ganglion cells. Curcio noted, “we found a second population of cells right in the foveal center that looked just like Müller glia,” but with a truncated vertical extent. The group termed these cells “inner Müller cells.”

She emphasized that it remains unclear whether this cell type is unique to prematurity or has simply been overlooked: “it’s possible that it’s been there all along… but it took volume electron microscopy to see it.” Curcio suggested that, under certain conditions, these cells might be detectable with clinical imaging if ophthalmologists know to look for them.

Importantly, the donor did not have retinopathy of prematurity, underscoring that prematurity-related visual consequences extend beyond ROP and reflect broader neurodevelopmental effects. Curcio highlighted growing evidence that prematurity is a lifelong condition and raised questions about links between low birth weight and later retinal disease, including age-related macular degeneration.

Curcio's goal in presenting these data clinically was explicit: “to stimulate thought among ophthalmologists” who image the fovea daily, and to encourage reinterpretation of foveal structure in health and disease in light of a newly recognized Müller glial population.

Reference

1. Curcio CA. Unusual morphology of foveal Müller glia in an adult human born preterm. Presented at: FLORetina 2025–International Congress on OCT and OCT Angiography (ICOOR); December 4-7, 2025; Florence, Italy.