Luminance-modulated adaptation in the global flash mfERG: a preliminary study of early retinal functional changes in high-risk glaucoma patients

Abstract

To investigate the association of the luminance-modulation global flash multifocal electroretinogram (mfERG) and other clinical assessments of vision in subsets of subjects at high risk of developing glaucomatous damage. Eighteen subjects (28 eyes) with asymmetric glaucoma and ocular hypertension were measured in this longitudinal study of visual field, OCT, and multifocal electroretinogram (mfERG). Five ophthalmic examinations were scheduled, once every 12months over a 4-year period. The mfERG was assessed using a luminance-modulated global flash stimulation paradigm. The adaptive index which we have reported previously was calculated. There was a significant thinning of the peripapillary retinal nerve fiber layer over the course of the study for eyes with ocular hypertension, or for fellow eyes with asymmetric glaucoma which initially had an abnormal adaptive index; such eyes showed a thinning rate of -3.59 and -3.69μm/year, respectively. However, no significant thinning was found for eyes which initially had a normal adaptive index. Two subjects were shown to have glaucomatous damage, confirmed by abnormal thinning of the retinal nerve fiber layer and visual field loss respectively at the last visit. However, these patients had shown an abnormal adaptive index in the mfERG measurement at the first visit. The adaptive index calculated from the measurement of luminance-modulated global flash mfERG is useful for predicting progression of signs related to glaucoma, especially in high-risk groups. The abnormal adaptive index reflects the change in fast-adaptive mechanisms in the retina and indicates the risk of developing glaucoma.