Peripheral contrast sensitivity and its contribution to myopia onset

Visual information is central to eye growth and development of myopia. Research into genetic and environmental factors promoting myopia has shown that abnormal contrast signaling between adjacent retinal cones is able to cause axial elongation of the eye globe. Patients with myopia show increased contrast sensitivity in mid-peripheral fields of vision, which can promote myopia progression during the active eye growth in children. High myopia, which is associated with the LVAVA and LIAVA haplotypes of the opsin gene, is believed to be explained by disruption of signaling that is triggered by light absorption by photopigments located in L- and M-cones and that regulates emmetropization. Bipolar cells have receptive fields around their centers that activate contrast produced by distinct images. Their lowest activity was observed in response to blurred images, when the light is evenly distributed across the receptive field. The light affecting a cone normally causes it to hyperpolarize; however, this process may be affected by feedback from adjacent cones that are also activated when the lighting is homogeneous. The studies evidence that not only myopic or hyperopic image defocus contribute greatly to abnormal eye growth, but also changes in contrast sensitivity in the near peripheral retina. Therefore, studies of optical correction methods, i.e., of peripheral defocus and peripheral contrast–modulating spectacles and contact lenses, are ongoing. Thus, peripheral contrast sensitivity is essential in visual adaptation and eye growth. Changes in peripheral contrast sensitivity may promote myopic refractive response, adding to peripheral defocus. This opens up opportunities for further development of optical methods for management of progressive myopia in children.