Imaging and the perspective of clinical electrophysiology

Clinical electrophysiology allows a detailed analysis of retinal function in various disorders. When for decades the morphological examination of the retina was limited to ophthalmoscopy and fluorescein angiography, electrophysiological techniques allowed detection of retinal abnormalities in morphologically ‘‘normal’’ retina: e.g. cone dystrophies with the fullfield ERG, early stages of macular dystrophies with the pattern ERG (PERG) or multifocal ERG (mfERG), early stages of chloroquine retinopathy with the mfERG, non-manifesting carriers of Best disease with the EOG or retinal ganglion cell damage in autosomal dominant optic atrophy with the VEP. In recent years, new techniques for the evaluation of retinal morphology have been introduced in clinical practice. Optical coherence tomography (OCT) within the last 15 years has evolved from frequency domain techniques to the fourth generation with spectral domain techniques, and further development with even higher resolution and additional possibilities is only a question of time [1]. The OCT has changed our understanding of retinal morphology in several diseases and, in addition, has allowed the detection of subclinical alterations, which are difficult to visualize otherwise, e.g. residual subfoveal fluid after retinal detachment surgery or beginning retinal edema in diabetic maculopathy or retinitis pigmentosa [2]. New non-invasive imaging devices allow the detection of autofluorescent pigments in the retinal pigment epithelium (RPE) with different wavelengths of autofluorescence, predominantly lipofuscin (fundus autofluorescence, FAF) and melanin (near-infrared autofluorescence, NIA) [3, 4]. Increased production of lipofuscin is associated with multiple degenerative disorders in the photoreceptorRPE complex. FAF allows us to determine structural integrity of the RPE and to define areas of degenerative activity. FAF can be used for early detection of retinal dystrophies or chloroquine retinopathy, or for separation between nevi or small uveal melanomas. The utility of FAF has been demonstrated in small children in whom electrophysiology is difficult to perform [5]. More recently near-infrared autofluorescence has been introduced which promises additional information in retinal dystrophies or degenerations and ocular tumours [4, 6]. The development of new retinal imaging techniques results in certain disadvantages and advantages for the experts in clinical electrophysiology. Disadvantages are predominately present in clinical U. Kellner (&) Retina Science, Bonn, Germany e-mail: kellneru@retinascience.de