Evidence exists that both the pattern electroretinogram (PERG) as a parameter of ganglion-cell function and computerized morphometric disc analysis (ONHA) predict subsequent glaucomatous visual field defects in ocular hypertensive eyes. Since November 1991 we have conducted a prospective longitudinal study to evaluate the suitability of PERG and ONHA for detecting incipient glaucoma damage. Inclusion criteria were: an intraocular pressure of > or = 25 mmHG (at least two measurements taken on different days) or, in eyes with additional risk factors, > or = 23 mmHG; a normal Octopus visual field (mean defect < or = 2 dB, no local defect); and no definite glaucomatous disc cupping. After a mean follow-up period of 14.6 +/- 8.8 (range 1-33) months and with a mean intraocular pressure of 24.4 (range 18-42) mmHg, none of the 66 patients (115 eyes) converted to glaucoma. Furthermore, PERG and ONHA do not agree in their estimation of the glaucoma risk at this stage.