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Eye Adaptation to Defocus Experiment in White Leghorn Chicks

Explore how the eyes of White Leghorn chicks adapt to defocus through induced states of hypermetropia and myopia using lenses. This experiment measures changes in the choroid and eye sensitivity to lens defocus.

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Eye Adaptation to Defocus Experiment in White Leghorn Chicks

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  1. Can eyes adapt to defocus? By: Kristian Galan Mentors: Frances Rucker & Olufunke Adeusi

  2. Introduction • The goal for this experiment is to see if the eye adapts to defocus. • Adaptation is when the eye changes its sensitivity to maintain good vision.

  3. Vocabulary • Choroid~ thin vascular layer between the sclera and the retina. It supplies blood to the retina and conducts arteries and nerves to other structures in the eye • Retina~ the nerve layer that lines the back of the eye. It senses light and creates impulses that travel through the optic nerve to the brain

  4. Vocabulary (cont’d) • Defocus~ when images aren’t focused directly on the retina • Lens~ used to correct defocused images. In this experiment we are inducing defocus with lenses. • Hypermetropia~ when an image is focused behind the retina • Myopia~ when an image is focused in front of the retina

  5. Equipment/tools • White Leghorn chicks • + and - lenses(+6, -6.5) • Ultrasound • Refractometer (Refraction) • Anesthetics

  6. Movie

  7. Procedure • Measurements of the chicks eyes are taken before exposing the chicks to the lenses, using both ultrasound and refraction • A negative lens was put on the chick’s right eye for 2 days to create a state of hypermetropia • The lens was taken off 4 times a day for 15 minutes each time to prevent the eye growing to compensate for the hypermetropia • On the third day we measured the eyes again. We then put positive lenses on both eyes of the chick to create a state of myopia for four hours. After that the eyes were measured again.

  8. Results

  9. Results (cont’d) • The choroid in the control eye did not thicken as much as the choroid in the experimental eye. • The choroid response in the experimental eye was more sensitive to plus lens defocus. • The eye appears to adapt to having the minus lens on.

  10. Further experiments • Because we have only tried this with the minus lens, we plan to do the same experiment using positive lens first followed by a minus lens.

  11. References • http://www.crypticscriber.com/dump/eye.gif • http://www.dblink.org/images/et-fig9.JPG • http://www.Medterms.com

  12. Acknowledgements • Dr. Frances Rucker • Olufunke Adeusi • CCNY • Dr. Sat • Harlem Children Society

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