Postreceptoral adaptation abnormalities in early age-related maculopathy

Abstract

Age-related maculopathy (ARM) has become the major cause of blindness in the Western World. Currently its pathogenesis and primary site of functional damage is not fully understood but ischemia is believed to play a major role. Early detection and precise monitoring of progression of ARM are main goals of current research due to lack of sufficient treatment options, especially in the dry, atrophic form of this disease. We applied the multifocal electroretinogram (mfERG) that can detect any local functional deficit objectively in the central retina. We recorded two paradigms in early ARM patients, the fast flicker and the slow flash paradigm which both represent fast adaptation processes of the proximal retina but under differing photopic conditions and stimulation rates. By subtracting the waveform responses we extracted a late component in the difference waveform that was significantly reduced in the early ARM group compared to a healthy control group (p < or = 0.05). We propose that this multifocal nonlinear analysis permits the detection of adaptative deficits and provides topographic mapping of retinal dysfunction in early ARM. The difference waveform component we extracted with this novel approach might indicate early functional loss in ARM caused by ischemia in postreceptoral layers such as bipolar cells and inner plexiform regions.

Age‐related maculopathy in the light of ischaemia

“…Analysis of the global flash mfERG revealed a significant reduction of its early waveform component (DR) in the early ARM group compared to the age‐similar healthy group (Figure 1B). We inferred that both waveform components reflected post‐receptoral functional deficits located within the ON and OFF bipolar cells and the outer and inner plexiform layer in early ARM 69 …”

“…Psychophysical function tests have not yet separated primary receptoral and post‐receptoral deficits 67,68 . We have applied an electrophysiological technique for measuring post‐receptoral responses by using the multifocal electroretinogram (mfERG, Veris Science 5.1.5X, EDI Inc, Redwood City, CA, USA) 11,69 . In its conventional, fast flicker application, the mfERG measures cone‐mediated ON and OFF bipolar cells but also inner retinal cell contributions 70 .…”

“…67,68 We have applied an electrophysiological technique for measuring post-receptoral responses by using the multifocal electroretinogram (mfERG, Veris Science 5.1.5X, EDI Inc, Redwood City, CA, USA). 11,69 In its conventional, fast flicker application, the mfERG measures cone-mediated ON and OFF bipolar cells but also inner retinal cell contributions. 70 According to the ischaemia postreceptoral hypothesis, these are the most susceptible areas to ischaemia.…”

The electroretinogram: a useful tool for evaluating age-related macular disease?

“…Various studies have reported the efficacy of the mfERG in the assessment of ARMD [6,19,20,29,33,[39][40][41][42][43][44][45][46][47][48][49][50][51][52][53][54][55][56][57][58].…”

“…The slow flash mfERG is another paradigm that has been subtracted from the conventional fast flicker mfERG to assess non-linear adaptive components within the retina in ARM [48]. Interestingly, neither conventional mfERG nor slow flash mfERGs discriminated between the ARM group and age-similar controls.…”