1. PHYL2027 Saccadic Oscillations and the Avian Pecten John D. Pettigrew Vision Touch and Hearing Research Centre, University of Queensland 4072 Australia.

2. The Fundus Oculi of Birds Action of opthalmoscope Pecten (=fan or comb) oculi No retinal blood vessels Keel-shaped morphology Diverse forms

3. Principle of the Ophthalmoscope: Eyeball to eyeball: Note that both retinas are congruent. Both can see each other clearly! Except for the fact that they block each other’s light

4. Eyeball to eyeball: Note that both retinas are congruent. Both can see each other clearly! Except for the fact that they block each other’s light.

5. Helmholtz’ Solution: Interpose a light source between the two eyes, through a small prism that does not obstruct the view.

6. Light source Prism

7. Looking into an owl’s eye

8. TMS Coil

9. Coil

10. Coil

11. Coil

12. Coil

13. Coil

14. Coil

19. Coil

20. Coil

22. Recording Eye Movements: Search coil technique Scleral coil of wire High frequency alternating e/m field Current induced in coil gives eye position

25. Saccadic Oscillations Birds only Frequency inversely proportional to mass of eye 60 Hz zebra finch------------10 Hz emu 1 cycle (Pacific Baza) to 20 cycles (Kingfishers) Repetition rate: 2 Hz (chick) to 0.1 Hz (owls) Axis of rotation: A-P i.e. torsional

27. Fluorescein “Angiography” in Birds Intravenous fluorescein View fundus Slow accumulation of fluorescein at pecten Fluorescein distributed by saccadic oscillation Need long inter-saccadic interval to observe Frogmouth an ideal subject

34. 3 Different Styles of Retinal Perfusion: 1. Mammalian: Blood Vessels in the way 2. Avian: “Downtime” from oscillations 3. Megabat: Focal plane broken up

37. Why Birds Can Detect Small, Eccentric Targets that are Invisible to Humans until they are Imaged on the Fovea.

38. Human Owl