Lye elongation during accommodation assessed by partial coherence inteferometry

Purpose. Several studies demonstrate a positive correlation between near work and progression of myopia. Biometrie changes of the anterior and posterior eye segment during accommodation arc measured using partial coherence interferometry (PCI), with a precision more than tenfold better as compared to ultrasound. Methods. Thirty eyes of 20 emmetropie and myopic subjects (age: 20 to 30 years) are measured. The spherical equivalent refraction ranges from +1.0 to -9.5 diopters. Conical thickness, anterior chamber depth, lens thickness and vitreous length are obtained during monocular fixation at the far and near point. Due to a special interfcrometric setup. PC'1 enables non-invasive biometry of axial length with an unprecedented precision of better lhan 5 urn. ResuIts. During maximum accommodation, axial eye length increases by 11 i 2.1 p.m in emmétropes and by 5 + 1.9 urn in myopes. Myopic eye elongation is significantly less pronounced than in emmetropie eyes (p.OOl ). Moreover axial eye length change and refraction are significantly correlated. Besides a decrease of anterior chamber depth and a thickening of the lens, the posterior lens pole moves an average of 70 ±39 fim posteriorly during maximum accommodation. Conclusion. In all subjects axial eye length increases during accommodation. This increase is significantly less in myopes. In contrary to the common view, the posterior lens pole moves posteriorly during accommodation. 'I he e\e elongation during accommodation is possibly a contributing factor to the development and progression of myopia.