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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.

Cone electroretinograms (ERGs), elicited by different color flashes under Ganzfeld conditions, were recorded from 6 patients with multiple evanescent white dot syndrome (MEWDS). All of the patients had normal color vision as determined by the Farnsworth Panel D-15 except for one who showed non-specific errors. The b-waves elicited from short wavelength sensitive (S-) cones were reduced more than the mixed long (L-) and middle (M-) wavelength sensitive cones in the affected eyes. The ratio of the S-cone b-wave amplitude of the affected eyes to that of the normal fellow eyes was significantly lower than the comparable ratio for the L- and M-cone ERG b-waves (p= 0.012). The S-cone ERGs recorded from 2 patients recovered to normal levels after their symptoms abated. These ERG results indicate that the S-cone system is more impaired than the L- and M-cone systems in the acute stage of MEWDS, and the changes in the S-cones may be reversible.

Cone electroretinograms (ERGs) elicited by different chromatic stimuli were recorded from patients with typical retinitis pigmentosa (RP) younger than 50 years of age. Ganzfeld color flashes on a bright white background illumination were used to elicit short-wavelength-sensitive (S-), and mixed long- (L-) and middle- (M-) wavelength-sensitive cone ERGs. Three patients with dominant inheritance, 22 patients with non-dominant inheritance, and 27 age-similar normal subjects were compared. Although the b-wave amplitudes of both the S- and L,M-cone ERGs were reduced in the RP patients, the S-cones were reduced to a greater degree than the L,M-cones. No significant difference in the S-cone reduction was observed between patients with dominant inheritance and those with non-dominant inheritance. The selective reduction of the S-cone system, reported previously in psychophysical studies, may be attributable not only to the macular region but also to the entire retina.