Recent insights from animal myopia research

1. Recent insights from animal myopia research Christine Wildsoet University of California - Berkeley

2. Animal models for myopia - Common animals & paradigms

3. Important questions • Do similar mechanisms underlie lens-induced- & form deprivation-myopia? • How do eyes distinguish between myopic & hyperopic defocus? • What signals pass from the retina to the sclera? • Can animals be used to model the refractive effects of eye diseases

4. The lens defocus models

5. Form Deprivation-Myopia & Lens-induced Myopia are different Lens defocus is a better model for the more common form of human myopia.

6. Refractive compensation to imposed defocus (active emmetropization) in chicks

7. Important questions • Do similar mechanisms underlie lens-induced- & form deprivation-myopia? • How do eyes distinguish between myopic & hyperopic defocus? • What signals pass from the retina to the sclera? • Can animals be used to model the refractive effects of eye diseases

8. Light at night inhibits lens-induced but not form deprivation myopia 15 minutes of light every hour during the night Yew & Wildsoet (2002)

9. Important questions • Do similar mechanisms underlie lens-induced- & form deprivation-myopia? • How do eyes distinguish between myopic & hyperopic defocus? • What signals pass from the retina to the sclera? • Can animals be used to model the refractive effects of eye diseases?

10. Decoding defocus ZENK expression studiesindicates that theretina can differentiate between myopic & hyperopic defocus -BUT HOW?

11. Stimuli for decoding defocus • High spatial frequencies seem to be important for decoding myopic defocus • Abnormal growth can increase monochromatic aberrations • Eye growth is chromatically tuned

12. High frequency A-scan ultrasonography

13. Sign but not power of lens used to decode defocus Wildsoet & Wallman ARVO (1996)

14. Cues for decoding defocus Myopic example Diether & WildsoetARVO (2002)

15. High spatial frequencies & moderate to high contrast important for decoding myopic defocus 100% 65% 32% 16% 11%

16. Monochromatic aberrations & eye growth in chick Through-focus images of point source in imaging system Coletta, Marcos, Wildsoet et al. ARVO (2000)

17. 2.5 2 1.5 FWHM (min arc) 1 0.5 0 Hyperopes Emmetropes Myopes Refractive Error Type Induced myopia increases aberrations in chicks Angular double-pass image width varies slightly with refractive error

18. Important questions • Do similar mechanisms underlie lens-induced- & form deprivation-myopia? • How do eyes distinguish between myopic & hyperopic defocus? • What signals pass from the retina to the sclera? • Can animals be used to model the refractive effects of eye diseases?

19. How much of eye growth is controlled locally? Myopic growth is regulated locally but perhaps not hyperopic growth Wildsoet ARVO (2001)

20. “Myopia inducers”: Neither optic nerve section norciliary nerve section prevent effects

21. “Hyperopic inducers”: Optic nerve section but notciliary nerve section interferes with effect

22. Myopic defocus is more potent than hyperopic defocus Simultaneous exposure to myopic & hyperopic defocus results in hyperopia Wildsoet & Collins ARVO (2000)

23. Multifocal lenses & refractive changes

24. Myopic defocus (positive lenses) has a stronger effect than hyperopic defocus (ciliary nerve section)

25. Important questions • Do similar mechanisms underlie lens-induced- & form deprivation-myopia? • How do eyes distinguish between myopic & hyperopic defocus? • What signals pass from the retina to the sclera? • Can animals be used to model the refractive effects of eye diseases?

26. Albinism - A chick model

27. Natural emmetropization in albino chicks is abnormal

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