Measurement of the Photopic Negative Response of the Electroretinogram by Discrete Wavelet Analysis

The Electroretinogram (ERG) is the mass recording of the electrical activity of retina. The a-wave and b-wave, which reflect the outer retinal activity have been studied widely for various retinal conditions. The photopic negative response (PhNR) ,a component of the full-field, brief flash electroretinogram (ERG) that reflects retinal ganglion cell function is less studied. The PhNR has been reported to be abnormal in various ocular diseases including glaucoma, diabetic retinopathy, and idiopathic intracranial hypertension (IIH). An important limitation of previous studies of the PhNR is the subjective nature by which it is measured. Furthermore, a uniform standard for assessing the PhNR in visually-normal controls and in patients with ocular disease is lacking. The overall goal of the present thesis is to address these limitations by developing a discrete-wavelet-transform-based approach for identifying and quantifying the PhNR quickly and objectively and apply it to patients with known optic nerve dysfunction due to IIH to establish an objective metric of retinal ganglion cell dysfunction. Three specific aims are proposed to achieve the overall goal. Aim 1 will develop an approach based on wavelet analysis for application to the human ERG. Aim 2 will determine the frequency components and time range in the discrete wavelet transform (DWT) that correspond to the PhNR of the full-field human ERG. Aim 3 will evaluate the PhNR using wavelet analysis as an index of retinal ganglion cell (RGC) function in IIH. Data from this thesis will provide the first objective assessment of the PhNR in a patient population, setting the stage for the use of this methodology in clinical trials.