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Sharp vision: a prerequisite for compensation to myopic defocus in the chick?
S T Nevin1, K L Schmid, C F Wildsoet
1Center of Eye Research, Queensland University of Technology, Brisbane, Australia.
Current Eye Research
|April 17, 1998
Summary
Sharp vision is essential for chicks to compensate for induced myopia. Preventing sharp vision leads to increased myopia, while partial vision allows for partial compensation, highlighting vision
Area of Science:
- Ophthalmology
- Developmental Biology
- Animal Models
Background:
- Active emmetropization, the process by which the eye adjusts its focus, can be influenced by spectacle lenses.
- The debate continues regarding whether emmetropization is uni-directional or bi-directional.
Purpose of the Study:
- To investigate if access to sharp vision is necessary for compensation to experimentally induced myopic defocus in chicks.
- To further understand the mechanisms of active emmetropization.
Main Methods:
- Imposing myopic defocus using various positive lenses (+15 to +65 D) in chicks.
- Manipulating access to sharp vision using stand-off cones and optic nerve section.
- Measuring refractive errors and axial ocular dimensions.
Main Results:
- Complete preclusion of sharp vision prevented compensation and led to increased eye growth and myopia.
- Limiting sharp vision resulted in partial compensation.
- Higher power lenses progressively reduced compensation, with very high powers inducing myopia.
Conclusions:
- Sharp visual input is fundamental for the compensation of imposed myopic defocus.
- These findings provide insight into the role of vision in active emmetropization.