Abstract
Purpose :
Selective stimulation and adaptation of the retinal ON and OFF channels has been shown to have specific effects on contrast, choroidal thickness (ChT) and refractive development. We have presented dynamic ON and OFF stimuli and have measured ChT changes after 1h (humans) and ChT, dopamine and DOPAC release after 3h (chickens).
Methods :
Dynamic ON or OFF stimuli (developed under Visual C++ 8.0) consisted of about 2000 small squares that had a saw–tooth shaped monochrome grey temporal luminance profile, either with a rapid ON and slow linear decay (ON stimulus) or vice versa (OFF stimulus). All squares were randomly phase shifted with respect to each other at a cycle frequency of about 1Hz. Humans: 11 young subjects were asked to watch ON and OFF stimuli for 60 minutes that were presented on a large screen at 2.3m distance. ChT was determined with Spectral Domain Optical Coherence Tomography (HRA+OCT Spectralis, Heidelberg Engineering). Chickens were exposed to dynamic ON or OFF stimuli for 3 hours (n=7 in both cases) in a “chicken discotheque” (4 large computer screens represented the walls). ChT was determined by SD-OCT. Thereafter, retinal and vitreal dopamine (DA) and its metabolites (DOPAC and HVA) were analyzed by high-performance liquid chromatography (HPLC).
Results :
In humans, subfoveal choroid thickened, on average, by +5.31±2.03 µm (SEMs) after 1 hour ON, and thinned -4.71±0.55 µm after 1 hour OFF stimulation. In chicks, 3 hours of ON stimulation caused choroidal thickening (both eyes pooled, ON +26.91±6.68 µm, OFF -5.72±3.53 µm, p=0.0002, two-tailed unpaired t-tests) and higher vitreal DA levels compared to OFF stimulation (both eyes pooled, ON vs OFF: 0.60±0.06 vs 0.45±0.04, p<0.05). No significant changes were found in retinal catecholamines.
Conclusions :
We found small but significant choroidal thickening after dynamic ON and thinning after OFF stimulation for 1h in young human subjects. Similar effects were observed in chickens after 3h. The directions of changes in ChT match previous findings when subjects were reading text of different contrast polarities, assumed to stimulate either ON or OFF systems. Furthermore, we found that ON stimulation stimulated vitreal dopamine release while OFF stimulation reduced it. Since DA is assumed to inhibit myopia, the direction of changes in DA matches the expected changes in choroidal thickness.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.