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A Physiological Model to Measure Effects of Age on Lenticular Accommodation and Spherical Aberration in Chickens

¹ From the School of Optometry, University of Waterloo, Waterloo, Ontario Canada; and the ² Department of Neuroscience, University of Pittsburgh, Pittsburgh, Pennsylvania.

PURPOSE. To assess physiological accommodative function of intact intraocular lenses, as measured by focal length changes, in chickens of various ages.

METHODS. Eyes of white leghorn chickens, aged 0 days (hatchlings), 7 days, 14 days, 6 weeks, 1 year, and 2 years, were enucleated and the backs of the globes, except for the ciliary nerve and ganglion, were removed. The ciliary nerve and ganglion were suctioned into the tip of a suction electrode, and lenses were optically scanned before, during, and after accommodation. Accommodation was elicited by delivery of 30-Hz electrical pulses.

RESULTS. For all age groups, lenticular focal lengths for stimulated eyes were significantly shorter than for relaxed eyes, indicating that accommodation had been induced. Lenticular accommodative amplitudes decreased significantly with age, with reduced function occurring between 0 and 7 days and again between 14 days and 1 year. Although accommodation was associated with an increased spherical aberration in all age groups, the increase was significant only in some age groups.

CONCLUSIONS. Results showing reduction of lenticular accommodation concomitant with increasing age suggest that in spite of major differences in anatomy and physiology of the accommodative mechanism, chickens may become presbyopic. Results showing high amounts of nonmonotonic spherical aberration in hatchling lenses suggest inherently poor optics in these birds.

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