Abstract
Abstract: :
Purpose: Recent work has renewed interest in the pattern electroretinogram (PERG) as a test for glaucomatous damage.[1–3] To better understand the relationship between the PERG and visual field loss, patients with field defects confirmed on both static visual fields and multifocal visual evoked potentials (mfVEP) were studied. Methods: Thirteen patients with open–angle glaucoma and with unilateral field defects were recruited. PERGs, mfVEPs, and Humphrey 24–2 visual fields (HVF) were obtained from each eye of patients and controls. PERGs were recorded with DTL electrodes and the Espion system (Diagnosys) using both a transient [4] and a steady–state [1] paradigm. The mfVEPs were obtained using the VERIS system (EDI), three channels of recording, and analyzed with custom software as previously described [5,6]. Results: For the 13 patients, 15 eyes had abnormal HVF (significant clusters and abnormal GHT) while 13 eyes had abnormal mfVEPs (significant clusters). The HVF and mfVEP agreed in 24 of the 26 eyes. Of these 24 eyes, 13 had a defect (significant clusters in the same region), and 11 appeared normal, on both tests. PERGs were analyzed for these 24 eyes that had similar results on both HVF and mfVEP. Of various PERG measures, the ratio of P50toN95 to P50 of the transient PERG showed the best agreement with the HVF/mfVEP data. The PERG was outside the normal limits for 10 eyes and agreed with the HVF/mfVEP in 17 (71%) of the eyes. Of the 7 disagreements, 5 PERG were within normal limits, although the mfVEP and HVF showed clear defects. In these 5 cases, the abnormal region on HVF/mfVEP occupied an area less than a hemifield. Conclusions: Although the agreement between the PERG measure and the HVF/mfVEP was reasonably good, the PERG missed defects detected by both the HVF and mfVEP. For example, 5 eyes with PERGs within the normal range had local defects clearly visible on the mfVEP and HVF. This suggests that the PERG may miss local defects in some patients with glaucoma. 1. Bach (2001) Eur J Ophthal; 2. Porciatti & Ventura (2004) Ophthal; 3.Garway–Heath et al (2002) IOVS; 4. Graham (2001) Prog Ret Eye Res; 5. Hood & Zhang (2000); 6. Hood et al (2002) AO.
Keywords: electrophysiology: clinical • electroretinography: clinical • visual fields