An A-mode ultrasound unit was used to investigate how the principal refractive surfaces of the eye changed during the act of accommodation. Sixteen volunteers took part in an investigation where changes were studied in both the cyclopleged and noncyclopleged state. Measurements of axial length, anterior chamber, lens thickness, and vitreous chamber depth were made at three different accommodation response levels over time. The results showed no significant change in axial length or vitreous chamber depth of the eye from cycloplegia to any accommodative response level. The depth of the anterior chamber and thickness of the lens showed significant changes at each of the three accommodative response levels. These results are consistent with the Helmholtz-Fincham theory of accommodation. This study also demonstrated the time course of action of two drops of 1% cyclopentolate with full cyclopentolate cycloplegia reached between 35 and 45 minutes for subjects with dark irides.
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