Monocular transcorneal electrical stimulation induces ciliary muscle thickening in contralateral eye

Transcorneal electrical stimulation (TES) is a treatment method for retinal diseases like retinitis pigmentosa (RP) and has also been used to evaluate retinal sensitivity by determining phosphene thresholds, which are subjective luminance impressions caused by retinal stimulation.

A pilot study was conducted to investigate the effects of monocular TES on the ciliary muscle (CM, s. the figure), the structure responsible for near vision, and its impact on central accommodation control. The study involved ten healthy adults, and optical coherence tomography (OCT) imaging was used to assess morphological changes in the right eye's CM during monocular ipsi- and contralateral TES. The results showed that ipsilateral TES induced a thickening of the CM, suggesting potential effects on blood flow or interstitial fluid. Interestingly, the study found that also contralateral TES led to a thicker CM in the right eye, indicating involvement of the central control circuit of accommodation. A systemic effect might derive from a synchronization of neuronal activity in the visual pathway possibly elicited by the electrical stimulation. These findings have implications for the clinical application of TES and the current understanding of the accommodation process, as well as for research of presbyopia and myopia. If TES proves to also have neuromodulation effects on the CM function, it could be used for the treatment of accommodation insufficiencies and presbyopia, and as adjunct therapy for myopia control strategies in children. Click here to read the original article

*_{Credits to the structure of the eye figure: OpenStax College, CC BY 3.0 <https://creativecommons.org/licenses/by/3.0>, via Wikimedia Commons}