Abstract
Purpose :
The ciliary muscle plays a key role in the process of accommodation, allowing the crystalline lens to adjust its refractive power for near and far vision. With age, the lens becomes increasingly rigid, resulting in presbyopia. The ciliary muscle’s function is preserved, and its electrical potentials during accommodation can be recorded. We developed a wireless intraocular device to directly record the ciliary muscle’s biopotentials using a novel bipolar electrode placed in the ciliary sulcus. Here, we present first results recorded in a non-human primate eye.
Methods :
An implant (12x18mm) was designed to be placed under the superior rectus muscle (Fig.1). It consists of a microcontroller and a biopotential recorder that digitizes the signal. The recorded signals are transmitted via Bluetooth, and the hardware design reduces noise arising from this transmission. The firmware allows maximized battery (CR1025, li-ion) lifetime while maintaining high measurement accuracy. To protect the implant and improve its biocompatibility, it was coated with parylene and a silicone layer (Fig.1a). A novel differential electrode to be inserted into the ciliary sulcus records the electrical potentials of the ciliary muscle. It is placed on a capsular tension ring and comprises two concentric gold-coated rings connected by spokes (Fig.1a insert).
Results :
In vitro experiments showed that the implant can maintain low energy mode for several months and is capable of continuous recording for >80h. Tests using simulated biopotentials with a 2mV amplitude exhibited an effective resolution of 3.64µV. After successful implantation in the phakic eye of a cynomolgus monkey (Fig.1b), initial in vivo measurements revealed a consistent baseline (including drift typical for biosignal acquisition) with peaks during mechanical eye stimulation (Fig.2).
Conclusions :
Our wireless intraocular system designed to record the ciliary muscle’s electrical potentials during accommodation in vivo has been shown to deliver consistent baseline signals in the phakic eye of a cynomolgus monkey. Following animal training, the monkey will be tested in a setup with controlled presentation of accommodative targets. This will allow for correlating the biopotentials with the eye’s refractive state. Ultimately, the implant may lay the foundation for a biomimetic intraocular lens to restore accommodation in the presbyopic human eye.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.