Measurement of eye length and eye shape by optical low coherence reflectometry

Background: The precise and rapid measurement of eye length and eye shape a re essential for investigating eye growth regulation and myopia. For this p urpose, we developed an optical low coherence reflectometer and obtained pr eliminary measurements in volunteers. Methods: The instrument includes a rotating glass cube to produce longitudi nal scans at a velocity of 0.42 m/s and a repetition rate of similar to 13 scans/s. Heterodyne detection of light reflected from the anterior cornea a nd the posterior retina permits to measure axial eye length and eye shape t off-axis eye length). Each measurement consists of five consecutive scans. Reproducibility and precision were determined in one volunteer by measuring axial eye length five consecutive times, each time repositioning the eye. Eye shapes were determined in right eyes of four volunteers by measuring ey e length every 3.3 degrees from 10 degrees nasally to 10 degrees temporally . Results: Axial eye length measured repeatedly in one volunteer did not diff er between or within the measurements (one-factor ANOVA). The average stand ard deviation was 11 mu m. Eye shapes a) varied substantially among subject s and b) differed considerably from the corresponding shapes of spherical m odel eyes with identical axial eye lengths. Conclusion: The newly developed reflectometer permits the precise and rapid measurement of eye length and eye shape. Such measurements, especially in children, may provide important information about mechanisms of eye growth regulation and the development of myopia.