Biometric changes in the eyes of Norwegian university students - A three-year longitudinal study

Purpose: The aim of this study was to investigate the changes in biometric measurements and corresponding refractive errors during a three-year period among university students exposed to high educational demands. Methods: A three-year longitudinal cohort study was performed among 149 Nor wegian engineering students (79 females and 70 males, mean age 20.6+/-1.2 y ears) measuring their refraction and ocular dimensions at the beginning and at the end of the period. The examinations included refraction, keratometr y, and A-scan ultrasonographic measurements of the ocular components, all m ade in cycloplegia. Results: After three years the mean refractive change was -0.52+/-0.45 D (p <0.05), which was accompanied by a change in lens thickness of 0.07+/-0.10 mm (p<0.05), and a vitreous chamber elongation of 0.27+/-0.30 mm (p<0.05). The results refer to the right eye. Stratification of the sample based on t heir initial refraction (myopes, emmetropes, and hyperopes) showed refracti ve change towards myopia for all subgroups as well as a significant increas e in lens thickness and vitreous chamber depth. No significant three-year c hange in anterior chamber depth or corneal curvature was found in any of th e groups. For all groups, vitreous chamber elongation gave a notable dioptr ic change in myopic direction. Conclusions: A shift in refraction towards myopia after puberty is accompan ied by vitreous chamber elongation which can explain the dioptric change in myopic direction.