Non-invasive measuring of biopotentials of the ciliary muscle during accommodation in emmetropes.

To see near objects clearly, the ciliary muscle shapes the human eye's crystalline lens to adjust its refractive power, a process known as accommodation. This contraction of the ciliary muscle also results in an electrical potential change. Previous work from the 1950s and 1960s reported electrical voltages in the microvolt range that were attributed to the accommodating ciliary muscle, however without clarifying the interaction between lens and muscle. Here, we present data of 12 emmetropic participants using a custom-developed scleral contact lens electrode which enables to record accommodation-dependent biopotentials of the ciliary muscle with an accuracy up to the millivolt range. Therefore, participants alternately shifted their focus from far to various near targets while the biopotentials of the ciliary muscle and the actual refractive change of the crystalline lens were recorded by a contact lens electrode and an eccentric infrared Photorefractor. In addition, the impact of confounding biopotentials such as squinting and eye movements was investigated. Our research points to a potentially new objective method of measuring accommodative change. Understanding these biopotentials could lead to the development of self-focusing visual aids as an alternative way of vision correction in presbyopes.