Application of synchronous detector techniques for electroretinographic studies in patients with retinitis pigmentosa.

A description is given of the application of the Synchronous Detector technique for eleciroretinographic (ERG) measurements (cone function) in patients with retinitis pigmentosa. The results obtained, in terms of average amplitudes and average "delay time," are compared with the results obtained by conventional waveform averaging processes. Time delay measurements with the Synchronous Detector system are relatively independent of amplitude and precise waveform definition, and provide a convenient means of differentiating normal and abnormal responses. Very small signals can be measured with this system, and estimates of delay time can be obtained at levels where the usual (waveform) averaged responses have poor definition. A correlation of visual field loss with abnormal delay time is noted. The relationship of this method of signal analysis to the usual ERG interpretation is discussed briefly.