Built-in LED contact lens electrode for S-cone electroretinographic recordings.

Purpose: To characterize the cone electroretinograms (ERGs) elicited by chromatic stimuli obtained from a newly-developed contact lens electrode with built-in light-emitting diodes (LEDs) emitting different colors.

Methods: Cone ERGs were recorded from normal subjects with a contact lens electrode with built-in blue (430 nm), red (644 nm), and white LEDs. These LEDs have a wide range of luminance intensities (3 log units), and can be used as either the background illumination or the stimulus in any combination. The stimulus duration was fixed at 1 ms. For comparison, cone ERGs were recorded with Ganzfeld color flash stimuli using Wratten color filters on a bright white background.

Results: With a bright background illumination provided by the white LED (2.0 log cd/m2), the blue LED stimulus elicited an ERG with two positive peaks similar to that recorded with conventional Ganzfeld blue flashes. The peak time of the early b-wave was 24 to 28 ms, and that of the later one was 43 to 48 ms, and these values were identical to the L,M-cone and S-cone b-wave, respectively, elicited by Ganzfeld flashes. The ERGs elicited by the red LED lacked the second peak.

Conclusion: These results indicate that the S-cone and L,M-cone ERGs can be recorded simultaneously under the same background with this contact lens electrode. This relatively simple technique can be used to examine the human S-cone system in a routine clinical setting.