Abstract
Purpose :
Intrinsically photosensitive retinal ganglion cells (ipRGC) express the photopigment melanopsin. Melanopsin is present in the axons of ipRGCs that pass through the optic nerve head (ONH), which corresponds to the blind spot. Blue light stimulation of the ONH has been demonstrated to activate melanopsin. The synaptic pathway between ipRGCs and dopaminergic amacrine cells in the retina has implicated these cells in the light-mediated mechanisms regulating eye growth. This human experimental study addresses the hypothesis that axial length (AxL) decreases with repetitive daily blue light stimulation of the ONH over a 6-day period.
Methods :
Three emmetropic and 3 myopic volunteers (30 to 35 years) participated in this study over 9 consecutive days. Each stimulation day, volunteers underwent one 1-minute period of ONH stimulation with a flickering light using a VR headset (MyopiaX®, Dopavision GmbH, Germany). The first two days served as controls, with stimulation of the ONH by red light (620 nm, 22 cd/m2) on Day -1 and no stimulation on Day 0, followed by daily stimulation by blue light (460 nm, 22 cd/m2) on Days 1 through 6. AxL was measured with optical biometry (Lenstar LS 900, Haag-Streit AG, Switzerland) prior to any stimulation on Day -1, serving as baseline, and then one day after each period of ONH stimulation. A linear mixed model was used to analyze the changes in AxL relative to baseline with ONH stimulation and refractive error.
Results :
A significant interaction between ONH stimulation and refractive error was found for the changes in AxL (p<0.05). The change in AxL after 6 days of blue light stimulation amounted to -20±7 µm (Mean±SEM) in myopes (p<0.05) and -1±7 µm in emmetropes (n.s.). No significant differences were observed between the AxL changes with red light and no light control conditions.
Conclusions :
The results of this study indicate that repeated ONH stimulation by blue light may have the potential to reduce axial length, presumably through increased choroidal thickness. The effect appears to be more pronounced in myopes. These data in adults may have promising implications for the treatment of progressive myopia in children and adolescents by repeated blue light stimulation of the ONH via an innovative digital technology.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.