Investigating focal macular electroretinogram function for fundus‐related perimetry application

Abstract

Aims/Purpose: This study aimed to investigate the utility of focal macular electroretinogram (ERG) function in fundus‐related perimetry (microperimetry) for assessing cryptogenic diseases such as macular dystrophy. The decline in visual sensitivity of the retina was measured using microperimetry, and the retinal layer causing this decline was identified using multifocal ERG.A focal macular ERG function was used for microperimetry instead of multifocal ERG.Methods: The developed apparatus comprised illumination and photographic optical systems separated by a mirror with a hole, a microperimetry optical system and an ERG optical system separated by a 45° cold mirror. It also consisted of an Edmund infrared camera EO‐50231, a lens, a halogen lamp, an objective lens, four double convex lenses, two aperture stops, a mirror, a 12.1‐inch high brightness (2000 cd/m2) monitor and an artificial eye. Its electrical measuring equipment included a differential amplifier, a high‐pass filter, a 50‐Hz notch filter and two non‐inverting amplifiers. Moreover, the equipment consisted of the National Instruments' I/O device USB‐6216, a shielded connector block, plate electrodes, an electromagnetic shield sheet and the LabVIEW 2018 software for data retrieval. To perform the focal macular ERG, a DynaScan 49‐inch ultrahigh brightness (3500 cd/m2) liquid crystal display (LCD) was prepared.Results: The ERG software could display three stimulus spot circles with diameters of 5°, 10° and 15° on the ultrahigh brightness LCD. Additionally, a function for adjusting the size of the stimulus spot circle was added as the diameter was changed from 1° to 15°. The focal macular ERG was able to measure a wave, b wave and photopic negative response (PhNR). It was found that certain small waves on the b wave were confirmed with high probability as oscillatory potentials (OPs), while one positive wave similar to the d wave was confirmed sometimes; however, the c wave was not confirmed.Conclusions: It can be concluded that when not only the a wave, b wave and PhNR but also the OPs and d wave are confirmed, the focal macular ERG function can identify the retinal layer causing visual alterations at specific points throughout the retina.