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The pathophysiology and pathogenesis of myopia are still a matter of controversy. Exaggerated longitudinal eye growth is assumed to play an important role in the development of myopia. A significant correlation between refraction and amount of near-work has been reported. However, current knowledge of changes of axial eye length with accommodation is limited because clinical ultrasound biometry does not provide the precision and resolution required to thoroughly investigate these phenomena. Partial coherence interferometry (PCI), a noninvasive biometric technique, uses laser light with short coherence length in combination with interferometry to achieve precision in the micrometer to submicrometer range and resolution of 10 microm. In the present study this technique was used to investigate axial eye length changes in 11 emmetropic and 12 myopic eyes during monocular fixation at the far and near point. In 7 subjects, the contralateral eye has also been measured to investigate interocular differences in eye elongation. All investigated eyes elongated during accommodation. This elongation was more pronounced in emmetropes than in myopes (P< 0.001). Mean accommodation-induced eye elongations of 12.7 microm (range, 8.6-19.2 microm) and 5.2 microm (range, 2.1-9.5 microm), corresponding to a dioptric change of approximately-0.036 D and-0.015 D, were obtained for emmetropes and myopes. No significant difference in accommodative amplitudes between groups (5.1+/-1.2 D [range, 3.8-7.1 D] versus 4.1+/-2.0 D [range, 1.0-7.1 D]; P= 0.14) was detected. No significant interocular difference in …