Scan pattern and signal processing for optical coherence tomography

#The eye is critical for vision, and people need to see. The eye has a cornea and lens that refract light and form an image on the retina. The retina generates electrical signals in response to the image formed thereon, and these electrical signals are transmitted to the brain via the optic nerve. The fovea and macula of the retina have an increased density of cones in relation to other areas of the retina and provide crisp, sharp vision. Unfortunately, diseases of the retina can adversely affect vision even though other parts of the eye, such as the cornea and lens are healthy.

#Retinal thickness can be used to diagnose and monitor the health of the retina. Many patients who have been diagnosed with retinal vascular diseases and other diseases or conditions have an elevated retinal thickness and take or are treated with medications. Macular edema is an example of elevated retinal thickness which is often related to other diseases such as diabetes. Macular edema can also be related to other diseases such as age-related macular degeneration, uveitis, blockage of retinal vasculature, and glaucoma, for example. It would be helpful to know quickly if a medication is not working or requires re-administration so that treatment can be modified accordingly, and vision preserved. One way to do this is by making regular measurements of the thickness of a patient's retina. One technique used to measure the thickness of the retina is optical coherence tomography (OCT).

#Unfortunately, many prior OCT systems are overly complex and expensive and not well-suited to monitoring retinal thickness regularly, such as on a weekly or daily basis. The prior standard of eye care involves a visit to a health care provider who measures retinal thickness, but such visits require scheduling and appointments and can become expensive, especially if conducted on a weekly or daily basis. Many of the prior OCT systems are not well-suited for in-home monitoring or mobile health care. Such prior systems typically weigh more than a person can easily carry and are not-well suited to travel with the patient. In addition, the prior OCT systems are more complex than would be ideal, and not well-suited for everyday use and hazards such as being dropped. The prior cost of an OCT system may exceed what a typical patient can afford. Furthermore, use of a prior OCT system may require a trained operator. For the above reasons, in-home monitoring of retinal thickness has not been adopted as the prior standard of care and care of patients with retinal disease can be less than ideal in many instances.

#The novel features of the invention are set forth with particularity in the appended claims. A better understanding of the features and advantages of the present invention will be obtained by reference to the following detailed description that sets forth illustrative embodiments, in which the principles of the invention are utilized, and the accompanying drawings of which:

#FIG. 1A shows a simplified diagram of the human eye;

#FIG. 1B shows a perspective view of a monocular optical coherence tomography (OCT) device for measuring eyes of a user, in accordance with some embodiments;

#While various embodiments of the invention have been shown and described herein, it will be obvious to those skilled in the art that such embodiments are provided by way of example only. Numerous variations, changes, and substitutions may occur to those skilled in the art without departing from the invention. It should be understood that various alternatives to the embodiments of the invention described herein may be employed. For example, although reference is made to measuring a thickness of a sample such as the retina, the methods and apparatus disclosed herein can be used to measure many types of samples, such as other tissues of the body and non-tissue material. While reference is made to generating maps of retinal thickness, the methods and apparatus disclosed herein can be used to generate images of retinal samples, such as cross sectional or tomographic images.

#The presently disclosed systems and methods are well suited for incorporation with prior OCT approaches. The OCT interferometer may comprise one or more of a time domain OCT interferometer, a swept source OCT interferometer, spectral domain OCT interferometer or a multiple reflectance OCT interferometer. Although reference is made to a swept source VCSEL with a limited range of sweeping and the use of a plurality of VCSELs, the light source may comprise any suitable light source such as a MEMS tunable VCSEL capable of sweeping over a range of wavelengths from about 20 nm to about 100 nm or more. Although reference is made to retinal thickness maps, in some embodiments, the OCT measurement systems and apparatus are configured to generate 3D tomographic images of the retina. In some embodiments, the 3D tomographic images of the retina comprise high resolution image of the retina, with a spatial resolution along the OCT measurement beam within a range from 4 to 25 microns, for example with resolution within a range from 2 to 10 microns.

#The presently disclosed systems and methods can be configured in many ways. In some embodiments, the OCT system comprises a binocular device, in which one eye is measured and the other eye is presented with a stimulus such as a fixation stimulus. Alternatively, the OCT system may comprise a monocular device, in which one eye is measured at a time and only the measured eye is presented with a fixation stimulus, although the fellow eye may be covered with an occluder, for example.