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Abstract
The electrical response of the retina was examined as a function of retinal region, using stimuli of various spatial frequencies in the first experiment. In the second experiment, the regional response of the retina to defocus at high and low spatial frequencies was investigated. Twenty three subjects were recruited for global flash multifocal electroretinogram (mfERG) in experiment 1. Black and white gratings (printed on plastic transparent sheets) of four spatial frequencies (SF), 0.24, 1.2, 2.4 and 4.8 cycle per degree were presented in front of the mfERG stimulation. The amplitudes and implicit times of the direct (DC) and induced (IC) components of mfERG responses were pooled into six concentric rings for analysis. There was low amplitude DC at low SF, which increased with increasing SF, and which decreased with increasing eccentricity. The IC was high in amplitude at all SF and reduced in amplitude with increasing eccentricity. Our findings suggested that outer and inner retina had different characteristics in processing spatial details. In experiment 2, Twenty-three young adults were recruited for mfERG measurement. The retinal electrical responses for low (0.24cpd) and high (4.8cpd) SF under fully corrected conditions of short-term negative defocus (-2D) and short term positive defocus (+2D) conditions were measured. There was a sign-dependent response to defocus in the DC response, mainly in peripheral regions. The sign dependent response at low SF was more obvious than that at high SF, and was located more peripherally. The IC response showed no clear trends for either defocus condition. The human retina seems to have a decoding system for optical defocus, which was tuned for low spatial frequency, and was located in the retinal near periphery.
Highlights
With the exceedingly fast growing population of myopia in the world, myopia becomes an important global public health problem [1,2,3]
What types of visual stimulus are required for regulating the emmetropization? Visual stimulus projected onto the retina comprises a wide range of spatial frequencies, which plausibly tune the emmetropization [18,19,20,21,22]: Schmid and Wildsoet [21] found that exposure to spatial frequency within the range of 0.086 and 4.3 cycle per degree could inhibit form-deprived myopia in chick [21]
There is low amplitude DC with low spatial frequencies (SF) grating (0.24cpd), the DC amplitude increases with increasing number of gratings, and the DC amplitude decreases with increasing eccentricity at all eccentricities
Summary
With the exceedingly fast growing population of myopia (short-sightedness) in the world, myopia becomes an important global public health problem [1,2,3]. The relationship between sign-dependent changes in the messengers’ concentration and different signs of defocus (dopamine [28, 29], retinoic acid [30, 31] and glucagon [32, 33]) further supports that the retina responds to the signs of defocus. This compensatory activity manipulates the eye growth to achieve the clear retinal image. Since there is limited study for human, studying the retinal physiological interaction between the visual stimulus and optical defocus in human eye allows better understanding of the underlying mechanism in eye growth
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