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Corneal accommodation in chick and pigeon.

F Schaeffel, H C Howland

    Journal of Comparative Physiology. A, Sensory, Neural, and Behavioral Physiology
    |March 1, 1987
    PubMed
    Summary

    Changes in the bird

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    Area of Science:

    • Comparative physiology
    • Ophthalmology
    • Avian biology

    Background:

    • Accommodation is crucial for vision, allowing the eye to focus on objects at varying distances.
    • The mechanisms of accommodation differ across species, with the cornea and lens playing key roles.
    • Understanding avian accommodation is vital for comprehending visual adaptations in birds.

    Purpose of the Study:

    • To investigate the contribution of corneal radius of curvature changes to accommodation in birds.
    • To quantify the role of the cornea in natural accommodation in pigeons and chicks.
    • To explore the relationship between corneal shape and accommodative mechanisms in avian species.

    Main Methods:

    • Infrared photoretinoscopy was used to measure natural accommodation.
    • Infrared photokeratometry was employed to assess changes in corneal radius of curvature.
    • Measurements were conducted on adult pigeons and chicks.

    Main Results:

    • Corneal radius of curvature changes significantly contribute to accommodation in both chick and pigeon.
    • In adult pigeons, the cornea accounts for up to approximately 9 diopters of accommodation.
    • Corneal accommodation in chickens (approx. 8 D) is part of a larger accommodative range (15-17 D), with aspherical corneal properties potentially affecting measurements.

    Conclusions:

    • Corneal radius of curvature changes are a primary mechanism for accommodation in pigeons.
    • In chickens, corneal accommodation is significant but works in conjunction with other mechanisms.
    • The aspherical nature of the chicken cornea can influence the accuracy of photokeratometry measurements.

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