Phase-sensitive optical coherence tomography to measure optical aberrations in anterior segment
Techniques for measuring optical aberrations of the eye are disclosed. An example method comprises positioning the eye in a measurement location adjacent to a measurement arm of an optical coherence tomography (OCT) interferometer apparatus, so that source light from the measurement arm passes into the anterior segment of the eye and detecting an interference pattern, the interference pattern resulting from a combination of light reflected from the eye and light reflected from a reference arm of the OCT interferometer apparatus. Based on the interference pattern, an optical delay between a reference surface in the anterior segment of the eye and a measured surface in the eye is calculated, the reference surface being the anterior surface of the cornea or the lens, wherein said calculating comprises measuring an optical phase shift between the reference surface and the measured surface, based on the detected interference pattern.
1. A method for determining optical aberrations of the anterior segment of an eye, the method comprising:
positioning the eye in a measurement location adjacent to a measurement arm of an optical coherence tomography (OCT) interferometer apparatus, so that source light from the measurement arm passes into the anterior segment of the eye;
detecting an interference pattern from the OCT interferometer apparatus, the interference pattern resulting from a combination, in the OCT interferometer apparatus, of light reflected from the eye and light reflected from a reference arm of the OCT interferometer apparatus; and
based on the detected interference pattern, calculating an optical delay between a reference surface in the anterior segment of the eye and a measured surface in the eye, the reference surface being the anterior surface of the eye's cornea or the anterior surface of the eye's lens, wherein said calculating comprises measuring an optical phase shift between the reference surface and the measured surface, based on the detected interference pattern.
2. The method of claim 1 , wherein the method further comprises scanning the source light in a scan pattern across the measured surface in the eye, and wherein said detecting and calculating are repeated for each of a plurality of points in the scan pattern, so as to obtain an optical delay between the reference surface and the measured surface for each of the plurality of points.
3. The method of claim 2 , wherein the reference surface is the anterior surface of the eye's cornea and the method further comprises calculating an optical wavefront for the cornea, based on the distance between the reference surface and the measured surface for each of the plurality of points.
4. The method of claim 2 , wherein the reference surface is the anterior surface of the eye's lens and the method further comprises calculating an optical wavefront for the lens, based on the distance between the reference surface and the measured surface for each of the plurality of points.
5. The method of claim 2 , wherein the method further comprises determining a uniformity of the index of refraction of a component of the eye, based on the optical delay between the reference surface and the measured surface for each of the plurality of points and further based on OCT intensity data for the reference surface or the measured surface, or both.
6. The method of claim 1 , wherein the method is performed without a coverslip positioned between the eye and the measurement arm of the interferometer.
7. The method of claim 1 , wherein said detecting is performed using time-domain OCT.
8. The method of claim 1 , wherein said detecting is performed using spectral-domain OCT.