Interferometric measurement of the axial length of the eye

A fast and accurate fiberoptic-based interferometer for non- contact measurements of the axial length of the eye was constructed and tested. A novelty of the interferometer design is the use of a diffractive, bifocal lens, which simultaneously focuses on the cornea and on the retina. A superluminescent light emitting diode with a coherence length of 30 micrometers is used as light source. The axial length of the eye is measured by rapidly translating a reference mirror a distance covering the axial length. The estimated accuracy of a measurement is about 100 micrometer, a number which compares well with those of conventional ultrasonic-based measurements.