Post-natal refractive development of the eye matches optical power with axial length to focus the visual image onto the photoreceptors. When successful, the eye reaches emmetropia or zero refractive error. However, ~25% of the US population develops myopia while only 10% develop hyperopia. The prevalence of myopia has reached near epidemic proportions in Asian countries. Progressive myopes and high myopes have increased risk of retinal detachment and blindness. While ~$3.9 billion dollars was spent in 2001 on refractive corrections for distance vision (not including the cost of nearly 1 million refractive surgeries performed), no treatments exist to prevent or arrest the progression of myopia. The mechanisms driving refractive development have been localized to the retina, but the retinal pathways and biochemical signaling remain unknown. Based on the assumption that contrast sensitivity and spatial frequency are characteristics of the visual image that drive this response, we hypothesize that the main retinal pathways involved are the ON and OFF pathways. These pathways are proposed to stimulate unique biochemical signals that suppress default excessive eye growth. Thus, normal refractive development relies on constant biochemical feedback derived from retinal pathways activated by normal visual images. We further hypothesize that abnormalities in the visual environment, retinal pathways, or specific biochemical signals will result in down-regulation of the biochemical signaling which then allows for excess eye growth and myopia. In order to test this hypothesis, (Aim 1) the refractive development of specific mouse models with ON or OFF pathway defects will be tested under normal and form deprived visual conditions. In addition, the possibility that ON or OFF pathways originating from rod or cone photoreceptors may control refractive development will be tested by using mice with only functional rods or cones. Refractive development will be assessed by measurements of refractive error and ocular dimensions. The biochemical signals associated with the ON and OFF pathway will be investigated in Aim 2. We hypothesize that dopamine is a putative ON pathway signal. Thus, dopamine synthesis and release will be examined during refractive development in the ON/OFF pathway mutants as well as determining the consequence of the absence of dopamine on refractive development in a retina-specific dopamine deficient mouse. An OFF pathway biochemical signal will be identified using gene profiling in a mouse model with only functional OFF pathways. Candidate genes will then be tested in OFF pathway mutant mice. These experiments are designed to determine the retinal mechanisms of refractive development, thus identifying novel targets for pharmacological or behavioral interventions that could prevent or retard the development of myopia.
Uncorrected refractive errors represent the leading cause of blindness in the world and are the focus of the World Health Organization Vision 2020 program. In the US, ~25% of the population has myopia and an estimated $3.9 billion is spent annually for refractive correction of distance vision;not including the cost of renewed prescriptions or the nearly 1 million refractive surgeries that are performed annually. The proposed research will reveal new insights into the retinal mechanisms that control refractive development, thus identifying novel targets for new interventions that would prevent or retard refractive errors.
|Park, Han na; Jabbar, Seema B; Tan, Christopher C et al. (2014) Visually-driven ocular growth in mice requires functional rod photoreceptors. Invest Ophthalmol Vis Sci 55:6272-9|
|Chakraborty, Ranjay; Lacy, Kip D; Tan, Christopher C et al. (2014) Refractive index measurement of the mouse crystalline lens using optical coherence tomography. Exp Eye Res 125:62-70|
|Chakraborty, Ranjay; Park, Han na; Aung, Moe H et al. (2014) Comparison of refractive development and retinal dopamine in OFF pathway mutant and C57BL/6J wild-type mice. Mol Vis 20:1318-27|
|Barathi, Veluchamy A; Chaurasia, Shyam S; Poidinger, Michael et al. (2014) Involvement of GABA transporters in atropine-treated myopic retina as revealed by iTRAQ quantitative proteomics. J Proteome Res 13:4647-58|
|Pardue, Machelle T; Stone, Richard A; Iuvone, P Michael (2013) Investigating mechanisms of myopia in mice. Exp Eye Res 114:96-105|
|Park, Hanna; Tan, Christopher C; Faulkner, Amanda et al. (2013) Retinal degeneration increases susceptibility to myopia in mice. Mol Vis 19:2068-79|
|Stone, Richard A; Pardue, Machelle T; Iuvone, P Michael et al. (2013) Pharmacology of myopia and potential role for intrinsic retinal circadian rhythms. Exp Eye Res 114:35-47|
|Park, Han na; Qazi, Yureeda; Tan, Christopher et al. (2012) Assessment of axial length measurements in mouse eyes. Optom Vis Sci 89:296-303|
|Wisard, Jeffrey; Faulkner, Amanda; Chrenek, Micah A et al. (2011) Exaggerated eye growth in IRBP-deficient mice in early development. Invest Ophthalmol Vis Sci 52:5804-11|
|Wisard, Jeffrey; Chrenek, Micah A; Wright, Charles et al. (2010) Non-contact measurement of linear external dimensions of the mouse eye. J Neurosci Methods 187:156-66|