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Hydrostatic pressure changes behind chick and pigeon corneas are insufficient to account for corneal accommodation

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Abstract

Corneal accommodation accounts ~9 D of accommodation in pigeon eyes and for ~8 D of the full 15–17 D accommodative range in chicken eyes.1 The mechanisms of corneal accommodation are largely unknown. To test the role of intraocular pressure changes in corneal accommodation in chick and pigeon eyes we regulated the pressure behind excised corneas and measured the changes in corneal curvature. Curvatures of excised corneas with a hydrostatic pressure applied behind them were measured using IR keratometry. The radii of curvature of the excised corneas under hydrostatic pressure were similar to those measured in the living bird and in the intact excised eyes (six chick eyes 4.34–4.63 mm and four pigeon eyes 3.55–4.07 mm). Pressure changes regulated around physiological values2 (10–22 mmHG) resulted in small changes in corneal curvature (chicks 0.14–0.33 mm and pigeons 0.10–0.16 mm). When expressed as corneal refracting power (chicks 2.50–5.69 D and pigeons 2.36–3.20 D) the changes are insufficient to account for the full range of corneal accommodation.

© 1991 Optical Society of America

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