A versatile system for studying mammalian intraretinal metabolism and function in situ.

Microelectrodes can be introduced into the intact mammalian eye after the preparation has been stabilized with an animal head-holder and an ocular fixation ring. A versatile system for introduction and manipulation of the electrode consists generally of three coaxially orientated tube-like structures which interadapt in a telescopic fashion: an illuminator is threaded into the main body of a micromanipulator, the electrode, in turn, is threaded into the illuminator. The whole central axis therefore moves in unison as the micromanipulator is positioned or advanced by a remotely controlled hydraulic motion operating system. Two drive jacks, angularly attached to the main body, can move the central axis within a 38° conical plane around the vertical axis. Intravitreal and transretinal vertical movements (down to 2 μm) can be executed by coarse and fine controls respectively. The illuminator is used for intravitreal, fundic and electrode illumination as well as photo-stimulation (for electroretinography). PO₂ and pH microelectrodes have been successfully used in this system. Local electroretinograms can be made using the PO₂ electrode as the sensor. Simultaneous transretinal PO₂ measurements and electroretinography are theoretically possible using a single PO₂ electrode. Microelectrode measurements are generally made in a specially designed Faraday cage.