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Postnatal control of ocular growth: dopaminergic mechanisms
1Department of Ophthalmology, University of Pennsylvania School of Medicine, Scheie Eye Institute, Philadelphia 19104-6075.
Insights
Retinal dopamine helps control eye growth and vision. Apomorphine, a dopamine agonist, limits excessive eye elongation during visual deprivation in chicks and monkeys, suggesting a key role in vision-dependent eye development.
Area of Science:
- Ophthalmology
- Neuroscience
- Developmental Biology
Background:
- Postnatal eye growth and refractive error are regulated by vision-dependent feedback mechanisms.
- The retina is implicated as a key site for this feedback.
- Visual deprivation in animal models causes ocular enlargement and myopia, accompanied by reduced retinal dopamine levels.
Purpose of the Study:
- To investigate the role of retinal dopamine in regulating eye growth and refractive error.
- To determine if dopamine agonists can counteract the effects of visual deprivation on eye development.
- To explore the potential independent regulation of axial and equatorial eye dimensions.
Main Methods:
- Studies were conducted on neonatal chicks and rhesus monkeys.
- Visual deprivation was induced to promote ocular enlargement and myopia.
- Local application of the dopamine agonist apomorphine was used to assess its effects on eye growth.
- Retinal dopamine concentrations were measured.
- Axial and equatorial eye dimensions were measured in chicks.
Main Results:
- Visual deprivation led to increased ocular axial elongation and myopia, with decreased retinal dopamine.
- Apomorphine administration limited axial elongation during visual deprivation in chicks, but not equatorial growth.
- Preliminary data in rhesus monkeys suggest apomorphine eye drops suppress axial growth and myopia during visual deprivation.
- Axial and equatorial eye growth were found to be independently regulated in chicks.
Conclusions:
- Retinal dopamine plays a crucial role in the vision-dependent regulation of eye growth and refraction.
- Dopamine agonists like apomorphine show potential for limiting myopia progression.
- The findings support a retinal hypothesis for emmetropization, linking vision to ocular growth control.
Abstract:
A vision-dependent feedback mechanism contributes to the regulation of postnatal eye growth and refraction; this mechanism is located at least in part in the retina. In chicks and rhesus monkeys, visual deprivation leads to ocular enlargement and a myopic refractive error, and it also reduces the retinal concentration of dopamine. In neonatal chicks, local application of the dopamine agonist apomorphine limits the excessive axial elongation that is associated with visual deprivation. Both D1 and D2 dopamine receptor mechanisms may participate. Remarkably, apomorphine is geometrically selective, not limiting the exaggerated equatorial growth that occurs during visual deprivation. Preliminary results in neonatal rhesus monkeys indicate that apomorphine eye drops also suppress exaggerated axial growth and myopic refractive error during visual deprivation; equatorial diameters were not measured. Our observations are consistent with a retinal hypothesis for emmetropization and suggest that retinal dopamine participates in a mechanism linking ocular growth control to vision. In addition, we conclude that axial and equatorial dimensions are independently regulated in the chick.