The raised eye pressure experienced by people who have glaucoma puts physical pressure on the optic nerve, which results in loss of vision and, in many cases, blindness. Even with effective treatment, the damage has generally always been considered irreversible. Fresh hope comes from a German study that suggests this visual degeneration can be partially reversed.
The new clinical trial appears to change the outlook of patients with the condition after demonstrating significant vision improvement in partially blind patients who underwent 10 days of a noninvasive treatment called alternating current stimulation (ACS). According to lead investigator Dr. Bernhard A. Sabel of the Otto-von-Guericke University of Magdeburg, "ACS treatment is a safe and effective means to partially restore vision after optic nerve damage."
The study, Sabel says is “the first ever large-scale, multicenter clinical trial in the field of noninvasive brain modulation using electric currents and [it] suggests that visual fields can be improved in a clinically meaningful way." The results are published in the journal PLOS ONE.
For the study, the team looked at 82 patients, 33 with visual deficits caused by glaucoma and 32 who had anterior ischemic optic neuropathy caused by inflammation, optic nerve compression (due to tumors or intracranial hemorrhage), congenital anomalies or Leber's hereditary optic neuropathy. Eight of the participants had more than one cause of optic nerve damage.
The groups were randomized: 45 patients underwent 10 daily applications of ACS for up to 50 minutes per day over a two-week period while 37 patients received “sham stimulation.” This is a little like a placebo, where patients believe they are receiving treatment even though they are not. In fact, this study was double-blind, meaning it was set up so that for any given clinical session, neither the patient nor the person administering the stimulation knew if the treatment was genuine or not. This method helps scientists offset the placebo effect.
The team administered ACS by attaching electrodes to the skin near the eyes. No participants reported discomfort during stimulation, although the team says some temporary dizziness and mild headaches occurred in a few rare cases. Each person had his or her vision tested before treatment and then again 48 hours after its completion. Participants were then checked again, two months later, to see if there were any long-lasting changes.
The patients who had received ACS showed significantly greater improvements in the whole visual field than individuals in the “sham-treated” group. This amounted to a 24% improvement after treatment in the ACS group compared to a 2.5% improvement in the sham group. It was found that the ACS group also experienced significant recovery at the edges of the visual field.
These improvements from the treatment were still stable two months later — the ACS group showed a 25% improvement in the visual field while there were only negligible changes — only 0.28 percent — in the sham group.
The team says previous smaller studies have shown that well-synchronized dynamic brain functional networks are critical for vision restoration. Although loss of vision leads to de-synchronization, neural networks can be re-synchronized by ACS via rhythmic firing of the ganglion cells of the retina, activating or "amplifying" residual vision.
Sabel adds that "while additional studies are needed to further explore the mechanisms of action, the results warrant the use of ACS treatment in a clinical setting to activate residual vision by brain network re-synchronization." Although we’re still a little hazy on the finer points of neural synchronization, it seems the benefits are pretty plain to see.
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