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Aim To examine the influence of cloudy media on the slow double-stimulation multifocal electroretinogram (mfERG). Methods Slow double-stimulation mfERG responses were measured from 26 subjects with normal ocular health under normal and light scattering conditions (induced using acrylic sheets) (Experiment 1) and another nine cataract patients before and after cataract surgery (Experiment 2). The amplitudes and implicit times of the first (M 1 ) and second (M 2 ) stimulation were compared under normal and light scattering conditions in Experiment 1 and they were compared under precataract and postcataract surgery in Experiment 2. Results Compared with control conditions (normal and postcataract surgery), the M 1 amplitude in the central region was significantly reduced in light scattering conditions (acrylic sheets and precataract surgery); the M 2 amplitude and both M 1 and M 2 implicit times of all regions examined were moderately affected in precataract surgery. The M 1 :M 2 amplitude ratio and implicit time ratio were virtually unaffected in cloudy media for either central or mid-peripheral regions. Conclusion Cloudy media affects the mfERG amplitude and implicit time in the slow double-stimulation, but does not affect the response ratio (ie, M 1 :M 2 amplitude ratio and implicit time ratio) between the two stimulations. This suggests that the ratio analysis can be applied in patients with mild to moderately cloudy ocular media to evaluate the functional integrity of the retina.

Purpose This study investigated the retinal adaptive mechanism in inner retinal dysfunction using the slow double-stimulation multifocal electroretinogram (mfERG) paradigm. Methods Slow double-stimulation mfERG responses were recorded from 15 eyes of 15 4-month-old Mongolian gerbils in control conditions and after suppression of inner retinal responses with injections of tetrodotoxin (TTX) and N -methyl-d-aspartic acid (NMDA). The stimulation consisted of five video frames: the two initial frames with multifocal flashes were triggered by two independent m-sequences, followed by three dark video frames. The results were compared with findings in humans: 7 subjects with glaucoma and 31 age-matched normal subjects were measured using the same mfERG protocol. Results The stimulation generates two responses (M 1 and M 2 ) from the two independent multifocal frames. The M 1 :M 2 ratio showed a significant reduction after administration of TTX+NMDA in the animal study. This matched with the human glaucoma findings. Glaucoma subjects generally have a reduced M 1 :M 2 ratio; this ratio showed a sensitivity of 86%, with a specificity of 84% for differentiating normal eyes from glaucomatous eyes. Conclusion This stimulation paradigm provides a method of measuring temporal visual characteristics. The M 1 :M 2 ratio acts as an indirect functional indicator of retinal adaptation, which may be abnormal in the diseased retina. Further development of this method may help to describe the functional variation in the diseased retina and to predict the occurrence of a range of retinopathies.