An article to be published in Plos One describes how Inserm researchers have succeeded in preserving the visual function in rats suffering from glaucoma. This disease is associated with an abnormal increase in intraocular pressure and can lead to blindness. The team of researchers directed by Christophe Baudouin at the Institut de la Vision ((Inserm/CNRS/UPMC) focussed on inflammation-specific molecules: chemokines. Blocking one of the chemokines (CXCR3) led to reduced intraocular pressure, by restoring normal aqueous humour flow, thus protecting the retina and the visual function.

Glaucoma is the second leading cause of blindness across the globe, affecting fifty to sixty million people, 6-7 million of whom are blind. In France, approximately 800,000 people receive treatment for glaucoma. The disease is characterized by the progressive destruction of the optic nerve and an irreversible alteration to the visual function, generally associated with an abnormal increase in intraocular pressure.

This high intraocular pressure is caused by an obstruction to the normal aqueous humour flow on a specific ocular structure: the trabecular meshwork. However, there is little understanding of the degeneration of trabecular tissues, which causes this malfunction.

Current treatment for glaucoma does not directly target the original pathology of the trabecular meshwork.This could partly explain why treatment frequently fails, sometimes leading to blindness even with access to the best possible medical care.

The team of researchers directed by Christophe Baudouin at the Institut de la Vision is dedicated to studying physiopathological mechanisms responsible for glaucomatous trabecular pathology, and, more specifically, the role of specific “chemokine“ molecules in inflammation.

Several researchers from the team have recently demonstrated on the tissues of patients suffering from glaucoma, and on a human trabecular cell line, there is a balance between the CXCL12 chemokine and a truncated form of this molecule, SDF-1(5-67). Whereas the first molecule encourages the viability of trabecular meshwork tissues via the CXCR4 receptor, its other form causes the loss of the trabecular meshwork via the CXCR3 receptor. It would appear that the transition from a “healthy” form to a truncated form is driven by a specific environment and the cytokines and metalloproteases involved in glaucoma.

In a second phase, the researchers used an animal model of glaucoma and observed that blocking CXCR3 reduces intraocular pressure and restores the trabecular filter function, thus preserving the visual function by protecting the retina.

This research has improved understanding of glaucoma. As Alexandre Denoyer, the leading author of the publication explains: “The novel strategy targeting trabecular chemokines could result in the development of an innovative treatment to replace or complement current long-term treatment using eye drops”.

Using transcranial magnetic stimulation (TMS), an international team led by researchers from the Centre de Recherche de l’Institut du Cerveau et de la Moelle Epinière (CNRS / Inserm / UPMC) has succeeded in enhancing the visual abilities of a group of healthy subjects. Following stimulation of an area of the brain’s right hemisphere involved in perceptual awareness and in orienting spatial attention, the subjects appeared more likely to perceive a target appearing on a screen. This work, published in the journal PLoS ONE, could lead to the development of novel rehabilitation techniques for certain visual disorders. In addition, it could help improve the performance of individuals whose tasks require very high precision.

TMS is a non-invasive technique that consists in sending a magnetic pulse into a given area of the brain. This results in an activation of the cortical neurons located within the range of the magnetic field, which modifies their activity in a painless and temporary manner. For several years, scientists have been looking at the possibility of using this technique to enhance certain brain functions in healthy subjects.

In this respect, the team led by Antoni Valero-Cabré has carried out research involving the stimulation of a region of the right cerebral hemisphere known as the frontal eye field. Strictly speaking, this is not a primary visual area but it participates in the planning of ocular movements and the orientation of each individual’s attention in the visual space. In a first experiment, a group of healthy subjects tried to distinguish a very low contrast target appearing on a screen for just 30 ms. In some of the tests, the subjects received a magnetic pulse lasting between 80 and 140 ms on this frontal region before the target appeared. The researchers found that the success rate was higher when using TMS. The visual sensitivity of healthy subjects was temporarily increased by around 12%. In a second experiment, the subjects were shown a fleeting visual cue indicating the spot where the target could appear. In this configuration, the enhancement of visual sensitivity, which remained of the same order, was only apparent when the cue indicated the correct location of the target.

Although cerebral functions such as conscious vision are highly optimized in healthy adults, these results show that there is a significant margin for improvement, which can be “enhanced” by TMS. This technique could be tested for the rehabilitation of patients suffering from cortical damage, due for example to a cardiovascular accident, and for that of patients with retinal disorders. The second experiment suggests that rehabilitation based on both TMS and visual cues could be more selective than the use of stimulation alone. The researchers want to further explore this possibility using repetitive TMS, which, in this case, could make it possible to obtain long-lasting modification of cerebral activity.

Furthermore, according to the researchers, TMS could be used in the near future to increase the attentional abilities of individuals performing tasks that require good visual skills.

These experiments benefited from funding from the European ERANET NEURON BEYONDVIS initiative, partly financed by ANR.