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Frank Schaeffel, Min Wang, Andrea Carrillo Aleman; Reading white text on black background may cause less myopia than conventional black text on white. Invest. Ophthalmol. Vis. Sci. 2018;59(9):1171.
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Experiments by Crewther and Crewther in chickens (Neuroreport 2002, 2003), as well as studies in knock-out mice with deficient ON (Chakraborty et al Exp Eye Res 2015) or OFF pathway signalling (Chakraborty et al Mol Vis 2014) suggested that ON pathway activity represents an inhibitory signal for eye growth while OFF may be stimulatory. We have analyzed the strength of the ON and OFF inputs under various visual exposures and tested their effects on choroidal thickness in human subjects.
Software was written in Visual C++ for realtime analysis of the ON and OFF contributions in visual scenes. At 285,000 regularly spaced positions in video frames (640x480 pix), the gray levels of surrounding pixels were subtracted from the gray level of the center pixel. If positive, the position was considered ON stimulating, if negative, OFF stimulating. The analysis was done for different receptive field sizes, to read out the strength of ON and OFF stimulation at different spatial frequencies. Six young subjects (age 23-29) were tested with stimuli that preferentially stimulated either ON or OFF, presented on a 65” monitor at 2.5 m distance to reduce accommodation-related effects. Choroidal thickness was measured with the OCT Spectralis (Heidelberg Instruments Inc, Massachusetts, USA) and Lenstar LS 900 (Haag-Streit, Koeniz, Switzerland) before and after 30 and 60 min exposure. Screen brightness was matched to 35 cd/m2 for all stimuli.
(1) The most striking finding by the software was that natural scenes were balanced with regard to ON and OFF stimulation but that black text on white overstimulated OFF while white text on black overstimulated ON pathways, both for arabic and chinese text. (2) After reading black text on white for 60 minutes, the choroid had thinned in all subjects (on average of both eyes: -16.8±4.6µm, p<0.02). After reading white text on black background, the choroid had thickened (on average by +9.6± 7.1µm, p<0.0003).
Bi-directional changes in choroidal thickness can be induced in humans by overstimulating either the ON or OFF pathways, without changing focus or luminance. Reading black text on white overstimulates OFF, causes choroidal thinning and may induce myopia. Reading white text on black background stimulates ON, causes choroidal thickenning, and should have an inhibitory effect on myopia.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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