Visual improvement in glaucoma eyes has been a topic of interest ever since Dr. George Spaeth proposed decades ago that it would be the ideal outcome to aim for in the treatment of glaucoma. Over the last decade multiple publications, including one from our group, have shown that with significant and consistent IOP reduction, improvement of visual field can be demonstrated in some glaucoma patients. The working hypothesis here has been that moribund or partially dormant retinal ganglion cells (RGC) can recover with significant IOP reduction. In addition, recent OCT imaging studies have also demonstrated that reproducible and consistent anterior movement of the lamina cribrosa can be observed after marked IOP reduction with surgery.
As ophthalmologists, we have often assumed that this improvement is a result of redistribution of mechanical forces or improved blood flow to the optic nerve head and other modalities would be unlikely to be helpful. Sabel et al. summarize decades of animal and human evidence that such improvement can occur due to changes in the brain and propose that alternating current stimulation (ACS) can reliably achieve it in some patients. The proposed mechanisms, in addition to resurrection of unhealthy RGCs or 'silent survivors', consist of synchronization of neuronal oscillations and their temporal organization ('coherence'), and reorganization and amplification of spatial neural networking. Sabel et al. also propose that the high variability observed in damaged areas of the visual field is due to the fact that these regions are more susceptible to environmental and physiological influences and are functioning at their metabolic limits. ACS is hypothesized to affect brain plasticity and synaptic connections across the brain and optimize desirable neural networks in the brain. In a randomized trial on ACS, the best evidence available so far on this matter, Gall et al. demonstrated a modest improvement in visual field threshold sensitivity (about 10%) and other outcome measures immediately and two months after a ten-day course of ACS. It is important to note that the results are from patients with all types of neuropathy including glaucoma.
While the data provided in this review are promising, longer term findings would be essential to generalize these findings. It stands to reason that the results may not be permanent after a single ten-day course of treatment and that repeating the ACS would be necessary to maintain effect. The findings need also to be confirmed by other groups and in other patient populations.
Results may not be permanent after a single ten-day course of treatment and that repeating the ACS would be necessary