US researchers have identified an immune cell population that helps maintain normal intraocular pressure (IOP), potentially representing a new glaucoma treatment target. 

Writing in Immunity, the Duke University-led team reported that although macrophages have previously been observed in the conventional outflow pathway, their role in regulating IOP was not known. In mice, the researchers found these long-lived resident macrophages were concentrated in the trabecular meshwork and Schlemm’s canal, while monocyte-derived macrophages were more common around distal vessels. 

Selective depletion of the resident macrophages in mouse eyes led to raised IOP, increased outflow resistance and abnormal extracellular matrix remodelling in the resistance-generating tissues, they said. In contrast, depletion of monocyte-derived macrophages did not produce the same physiological changes.  

Lead author Dr Katy Liu said the work helps answer a longstanding question over whether the immune system directly regulates IOP. The team said disruption of this macrophage-mediated maintenance system could contribute to ocular hypertension and glaucoma pathogenesis. “Now we have a specific target for developing new therapies that can normalise the eye pressure and stop vision loss, in contrast to current medications that do not target the source of disease,” said Duke University corresponding author Distinguished Professor W. Daniel Stamer.