Graefe's Arch Clin Exp Ophthalmol (1989)227:123-130 Graefe's Archive for Clinical and Experimental Ophthalmology © Springer-Verlag 1989 The pattern-evoked electroretinogram (PERG): Age-related alterations and changes in glaucoma Matthias Korth, Folkert Horn, Brigitte Storck, and Jost Jonas Augenklinik der Universit/it, Schwabachanlage 6, D-8520 Erlangen, Federal Republic of Germany Abstract. Pattern-onset electroretinograms (PERGs) were studied in 147 normal subjects of different ages (14-79 years) and in 110 eyes of 65 patients with glaucoma or ocular hypertension. The responses showed an increase (P<0.001) in peak latency with increasing age and a de- crease (P< 0.001) in amplitude which approximately paral- lels the loss of ganglion cells estimated by other authors. Many glaucoma eyes showed a loss of the normally present spatial tuning. In the age group above 50 years 50% of the onset responses were significantly diminished and the peak latencies were not significantly different. A negative correlation (P<0.001) was found between the size of the PERG and the cup/disc ratio and a positive correlation (P<0.001) with the area of the neuroretinal rim of the optic disc. The PERG decreased (P< 0.01) with increasing visual field losses. Introduction The purpose of the present investigation is twofold: (1) to describe age-dependent alterations of the PERG in nor- mal eyes to establish reference values for clinical use and (2) to study the PERG in glaucoma eyes and to relate the findings with the normative data. In his monograph on the basis of clinical electroretinography, Karpe [32] intro- duced the electroretinogram (ERG) into routine clinical use for investigating and diagnosing various diseases of the eye. Normative data have been determined before for the now widely used flash-evoked ERG which showed typical ampli- tude decreases with increasing age [32, 47]. Because of the potential value of the PERG in differentiating optic nerve from retinal diseases the establishment of base values for different age groups is needed to make this method a useful part of routine electrodiagnostic testing. Typical stimuli applied in earlier studies were phase- reversing patterns generated on the screen of a TV monitor observed in direct view. With this technique certain precau- tions must be taken: Refraction must be corrected, the pupil size can be a problem [28, 51], and the luminance of the screen may be low. In the present study a Maxwellian-view system was used which alleviates these difficulties. Onset- offset stimuli [52] of high contrast were used since with this stimulus maximum responses are obtained with the on- set of spatial frequencies higher than the ones most fre- Offprint requests to : M. Korth quently employed (= spatial band pass or tuning, [32]). This indicates that this response is produced probably by center- surround receptive fields. Possible age effects which have only recently been communicated for the reversal PERG (see Discussion) were studied in a group of normals larger than the ones previously examined. Among the tests available to the ophthalmologist for studying glaucoma, electrophysiological procedures have not been standard in the past. The early study by Leyd- hecker [36], for instance, did not show a reduction in size of the conventional single flash ERG in glaucoma eyes. After signal averaging became available the study of visual evoked potentials (VEPs) resulted in findings related to glaucomatous defects. Recently, the averaging of ERGs to visual patterns has also led to useful results. The use of the PERG in optic nerve diseases in general was initiated by the reports of a nonrecordable PERG in patients and experimental animals with optic atrophy following damage to the optic nerve [25, 40, 41]. Several studies indicated a reduced PERG in glaucoma [7, 24, 29, 37, 44, 45, 49, 55] and even in ocular hypertension [3, 12, 60]. However, normal PERGs have also been de- scribed in glaucoma [11]. Many studies have shown that in glaucoma the VEP can be reduced in amplitude [10, 23] or increased in peak latency [6, 10, 30, 31, 51, 54], but a few simultaneous studies of both the PERG and the VEP [37, 45] indicated that the PERG is more often dis- turbed than the VEP. In addition, the observations of a reduced PERG in ocular hypertension may indicate that the PERG is an early indicator of optic nerve damage. Conventional single-flash ERGs were also studied in our patients to exclude defects that might be present in the outer retina. Since glaucoma is accompanied by changes of the optic disc and of the visual fields, relations between papillometric data and field defects with the PERG were also tested. Methods and materials The stimulus Onset-offset stimuli were applied as vertical square-wave stripe patterns of two fundamental spatial frequencies (0.2 and 3.4 c/deg). The diameter of the circular field was 22 degrees, the physical pattern contrast was kept constant at 0.97, and cross hairs kept at the edge of a stripe provided a central fixation mark. The stimuli were presented in a