Pattern electroretinogram (PERG) in the early diagnosis of normal-tension preperimetric glaucoma: a case report

INTRODUCTION: The purpose of this case is to present the use of pattern electroretinogram (PERG) in the early diagnosis of normal-tension preperimetric glaucoma in 56 years old woman. METHODS AND RESULTS: At baseline the results were as follows: distance-corrected visual acuity in the right eye (RE) and left eye (LE) 1.0 and 0.7, respectively (Snellen table), normal anterior segments in both eyes, normal fundus in the RE and abnormal cup to disc ratio (0.6) in the LE. Intraocular pressure (IOP) was within normal limits in both eyes: RE-14 mmHg, LE-18 mmHg (Goldmann tonometer). Results of standard automated perimetry (SAP), short wavelength automated perimetry (SWAP) and nerve fiber analyzer (GDx) were normal in both eyes. PERG result was normal in the RE but in the LE reduced amplitudes of P50 and N95 waves were observed. After topical treatment (Xalacom to the LE), a reduction of IOP to 13 mmHg was achieved and was accompanied by amplitudes increase of PERG waves. After discontinuation of the therapy, IOP increased to 18 mmHg and P50 and N95 amplitudes decreased to the values before treatment, suggesting the influence of IOP lowering therapy on electrical function of retinal ganglion cells. After 4 years from the baseline, static perimetry results were still normal, but abnormalities in retinal nerve fiber layer thickness were detected in GDx. CONCLUSIONS: PERG was a useful test not only for the early diagnosis of normal-tension preperimetric glaucoma, but also in evaluating the effectiveness of antiglaucomatous treatment.