Patent Description:
Current ophthalmic refractive surgical methods, such as cataract surgery, intra-corneal inlays, laser-assisted in situ keratomileusis (LASIK), and photorefractive keratectomy (PRK), rely on ocular biometry data to prescribe the best refractive correction. Historically, ophthalmic surgical procedures used ultrasonic biometry instruments to image portions of the eye. In some cases, these biometric instruments generated a so-called A-scan of the eye: an acoustic echo signal from all interfaces along an imaging axis that was typically aligned with an optical axis of the eye: either parallel with it, or making only a small angle. Other instruments generated a so-called B-scan, essentially assembling a collection of A-scans, taken successively as a head or tip of the biometry instrument was scanned along a scanning line. This scanning line was typically lateral to the optical axis of the eye. These ultrasonic A- or B-scans were then used to measure and determine biometry data, such as an ocular axial Length, an anterior depth of the eye, or the radii of corneal curvature.

In some surgical procedures, a second, separate keratometer was used to measure refractive properties and data of the cornea. The ultrasonic measurements and the refractive data were then combined in a semi-empirical formula to calculate the characteristics of the optimal intra-ocular lens (IOL) to be prescribed and inserted during the subsequent cataract phaco surgery.

More recently, ultrasonic biometry devices have been rapidly giving way to optical imaging and biometry instruments that are built on the principle of Optical Coherence Tomography (OCT). OCT is a technique that enables micron-scale, high-resolution, crosssectional imaging of the human retina, cornea, or cataract. OCT technology is now commonly used in clinical practice, with such OCT instruments are now used in <NUM>-<NUM>% of all IOL prescription cases. Among other reasons, their success is due to the non-contact nature of the imaging and to the higher precision than that of the ultrasound biometers.

Even with these recent advances, however, substantial further growth and development is needed for the functionalities and performance of biometric and imaging instruments.

<CIT> and <CIT> disclose OCT systems comprising one light source adjustable between source operating modes and corresponding mode-switching optics.

<CIT> discloses an SS-OCT with first light source for imaging the anterior segment and second light source for imaging the retina.

An optical coherence tomography (OCT) apparatus is defined in claim <NUM>.

A corresponding method is defined in claim <NUM>.

The embodiments described herein may be used to provide and/or operate an all-in-one device to achieve optimized OCT performance for each of several different application modes. Other advantages and variations of the above-summarized embodiments are described below.

In the following description, specific details are set forth describing certain embodiments. It will be apparent, however, to one skilled in the art that the disclosed embodiments may be practiced without some or all of these specific details. The specific embodiments presented are meant to be illustrative, but not limiting. One skilled in the art may realize other material that, although not specifically described herein, is within the scope and spirit of this disclosure.

Embodiments of the presently disclosed techniques and apparatus may be employed in both microscope-mounted and microscope-integrated Optical Coherence Tomography (OCT) systems. <FIG> illustrates an example of a microscope-integrated OCT system <NUM>, and is presented to illustrate the basic principles of OCT.

System <NUM> includes an eye-visualization system <NUM>, configured to provide a visual image of an imaged region in an eye <NUM>, an Optical Coherence Tomographic (OCT) imaging system <NUM>, configured to generate an OCT image of the imaged region; a refractometer <NUM>, configured to generate a refractive mapping of the imaged region; and an analyzer <NUM>, configured to determine refractive characteristics of the eye based on the OCT image and the refractive mapping. It will be appreciated that the OCT imaging system <NUM>, the refractometer <NUM>, and the analyzer/controller <NUM> can be integrated into the eye visualization system <NUM>.

The imaged region can be a portion or a region of the eye <NUM>, such as a target of a surgical procedure. In a corneal procedure, the imaged region can be a portion of a cornea <NUM>. In a cataract surgery, the imaged region can be a capsule and the (crystalline) lens <NUM> of the eye. The imaged region may also include the anterior chamber of the eye, which includes both the cornea <NUM> and the lens <NUM>. Alternatively, the imaged region may cover the full eye, including the cornea <NUM>, the lens <NUM> and the retina <NUM>. In a retinal procedure, the imaged region can be a region of the retina <NUM>. Any combination of the above imaged regions can be an imaged region as well.

The eye-visualization system <NUM> can include a microscope <NUM>. In some embodiments, it can include a slit-lamp. The microscope <NUM> can be an optical microscope, a surgical microscope, a video-microscope, or a combination thereof. In the embodiment of <FIG>, the eye-visualization system <NUM> (shown in thick solid line) includes the surgical microscope <NUM>, which in turn includes an objective <NUM>, optics <NUM>, and a binocular or ocular <NUM>. The eye-visualization system <NUM> can also include a camera <NUM> of a video microscope.

System <NUM> further includes the Optical Coherence Tomographic (OCT) imaging system <NUM>. The OCT imaging system <NUM> can generate an OCT image of the imaged region. The OCT imaging system can be configured to generate an A-scan or a B-scan of the imaged region. The OCT image or image information can be outputted in an "OCT out" signal that can be used by analyzer <NUM>, for example, in combination with an outputted "Refractive out" signal to determine biometric or refractive characteristics of the eye.

OCT imaging system <NUM> can include an OCT laser operating at a wavelength range of <NUM>-<NUM>,<NUM>, in some embodiments at a range of <NUM>-<NUM>,<NUM>. The OCT imaging system <NUM> can be a time-domain, a frequency-domain, a spectral-domain, a swept-frequency, or a Fourier Domain OCT system <NUM>.

In various embodiments, part of the OCT imaging system <NUM> can be integrated into the microscope, and part of it can be installed in a separate console. In some embodiments, the OCT portion integrated into the microscope can include only an OCT light source, such as the OCT laser. The OCT laser or imaging light, returned from the eye, can be fed into a fiber and driven to a second portion of the OCT imaging system <NUM>, an OCT interferometer outside the microscope. The OCT interferometer can be located in a separate console, in some embodiments, where suitable electronics is also located to process the OCT interferometric signals.

Embodiments of the OCT laser can have a coherence length that is longer than an extent of an anterior chamber of the eye, such as the distance between a corneal apex to a lens apex. This distance is approximately <NUM> in most patients, thus such embodiments can have a coherence length in the <NUM>-<NUM> range. Other embodiments can have a coherence length to cover an entire axial length of the eye, such as <NUM>-<NUM>. Yet others can have an intermediate coherence length, such as in the <NUM>-<NUM> range, finally some embodiments can have a coherence length longer than <NUM>. Some swept-frequency lasers are approaching these coherence length ranges. Some Fourier Domain Mode Locking (FDML) lasers, vertical-cavity surface-emitting laser (VCSEL)-based, polygon-based or MEMS-based swept lasers are already capable of delivering a laser beam with a coherence length in these ranges.

The example illustrated as system <NUM> further includes a refractometer <NUM> to generate a refractive mapping of the imaged region. The refractometer <NUM> may be any of the widely used types, including a laser ray tracer, a Shack-Hartmann, a Talbot-Moire, or another refractometer. The refractometer <NUM> can include a wavefront analyzer, an aberration detector, or an aberrometer. Some references use these terms essentially interchangeably or synonymously. A dynamic range of the refractometer <NUM> can cover both phakic and aphakic eyes, i.e., the eyes with and without the natural lens.

In some systems, the OCT imaging system <NUM> and the refractometer <NUM> can be integrated via a microscope interface <NUM> that can include a beam splitter 152c to provide an optical coupling into the main optical pathway of the microscope <NUM> or slit-lamp. A mirror <NUM>-<NUM> can couple the light of the refractometer <NUM> into the optical path, and a mirror <NUM>-<NUM> can couple the light of the OCT <NUM> into the optical path. The microscope interface <NUM>, its beam splitter 152c, and mirrors <NUM>-<NUM>/<NUM> can integrate the OCT imaging system <NUM> and the refractometer <NUM> with the eye-visualization system <NUM>.

In some embodiments, where the OCT imaging system <NUM> operates in the near infrared (IR) range of <NUM>-<NUM>,<NUM>, and the refractometer operates in the <NUM>-<NUM> range, the beam splitter 152c can be close to <NUM>% transparent in the visible range of <NUM>-<NUM>, and close to <NUM>% reflective in the near-IR range of <NUM>-<NUM>,<NUM> range for high efficiency and low noise operations. By the same token, in a system where the mirror <NUM>-<NUM> redirects light into the refractometer <NUM>, the mirror <NUM>-<NUM> can be close to <NUM>% reflective in the near IR range of <NUM>-<NUM>, and the mirror <NUM>-<NUM> can be close to <NUM>% refractive in the near IR range of <NUM>-<NUM>,<NUM>, redirecting to the OCT imaging system <NUM>. Here, "close to <NUM>%" can refer to a value in the <NUM>-<NUM>% range in some embodiments, or to a value in the <NUM>-<NUM>% range in others. In some embodiments, the beam splitter 152c can have a reflectance in the <NUM>-<NUM>% range for a wavelength in the <NUM>-<NUM>,<NUM> range, and a reflectance in the <NUM>-<NUM>% range for a wavelength in the <NUM>-<NUM> range.

<FIG> shows that the system <NUM> can include a second beam splitter 152b, in addition to the beam splitter 152c. The beam splitter 152c directs light between the objective <NUM> and the integrated OCT <NUM>/refractometer <NUM> ensemble. The beam splitter 152b can direct light between a display <NUM> and the binocular <NUM>. A third beam splitter 152a can direct light to the camera <NUM>.

The analyzer, or controller, <NUM> can perform the integrated biometrical analysis based on the received OCT and refractive information. The analysis can make use of a wide variety of well-known optical software systems and products, including ray tracing software and computeraided design (CAD) software. The result of the integrated biometry can be (<NUM>) a value of the optical power of portions of the eye and a corresponding suggested or prescribed diopter for a suitable IOL; (<NUM>) a value and an orientation of an astigmatism of the cornea, and suggested or prescribed toric parameters of a toric IOL to compensate this astigmatism; and (<NUM>) a suggested or prescribed location and length of one or more relaxing incisions to correct this astigmatism, among others.

The analyzer <NUM> can output the result of this integrated biometry towards the display <NUM>, so that the display <NUM> can display these results for the surgeon. Display <NUM> can be an electronic video-display or a computerized display, associated with the eye-visualization system <NUM>. In other embodiments, the display <NUM> can be a display in close proximity of the microscope <NUM>, such as attached to the outside of the microscope <NUM>. Finally, in some embodiments, display <NUM> can be a micro-display, or heads-up display, that projects the display light into the optical pathway of the microscope <NUM>. The projection can be coupled into the main optical pathway via a mirror <NUM>. In other embodiments, the entire heads-up display <NUM> can be located inside the microscope <NUM>, or integrated with a port of the microscope <NUM>.

In previously available systems, the OCT engine and optics of microscope-mounted or microscope-integrated OCT systems, such as the one illustrated in <FIG>, are non-configurable, with fixed system parameters, such as axial resolution, lateral resolution, and depth of focus. However, optimum system requirements for OCT differ, for different applications. For example, corneal and retinal applications typically require higher axial resolution than cataract-related procedures. Cataract applications, on the other hand, need a longer depth of focus for full-eye imaging or anterior-segment imaging, but typically obtain this longer depth of focus at the expense of compromised lateral resolution and axial resolution.

Various embodiments described herein provide microscope-based OCT apparatuses to flexibly address medical needs for cornea refractive, cataract, and vitreoretinal applications. As discussed in further detail below, the OCT engine and optics in various of these embodiments are reconfigurable, i.e., switchable, so that a single apparatus can provide optimum OCT performance for each of several operating modes or applications.

<FIG> illustrates another embodiment of a system <NUM>, in this case including mode-switching optics and laser-switching functionality consistent with some of the embodiments disclosed herein. While the basic functionality of system <NUM> is similar to that of system <NUM>, as illustrated in <FIG>, the components of system <NUM>, as illustrated in <FIG>, are grouped differently, for the purposes of discussion. It will be appreciated that the physical grouping may vary, from one embodiment to another.

System <NUM> includes a microscope unit <NUM>, a measurement head <NUM>, and an OCT console <NUM>, as well as a mode switching controller <NUM>. In some embodiments, measurement head <NUM> is mounted to a separate microscope unit <NUM>, while in others the components of measurement head <NUM> are integrated into a single unit with microscope unit <NUM>.

Microscope unit <NUM> may include some or all of the components shown in the eye-visualization system <NUM> of <FIG>, including the microscope <NUM>, which in turn includes an objective <NUM>, microscope optics <NUM>, up-beam and down-beam splitters 152u and 152d, and microscope binocular <NUM>. Microscope unit <NUM> may further include a display <NUM>, in some embodiments, and/or a camera <NUM>, in some embodiments, as illustrated in <FIG>. Because these details are not important to illustrate the operation of the mode-switching optics and laser-switching of the system <NUM> shown in <FIG>, these details of microscope unit <NUM> are not shown in <FIG>.

In the system <NUM> shown in <FIG>, the OCT system <NUM> is illustrated as a single block. In <FIG>, in contrast, the components of a configurable OCT imaging system are shown in more detail. In the example of <FIG>, these components are divided between measurement head <NUM>, which is integrated with or mounted on microscope unit <NUM>, and OCT console <NUM>. In some embodiments, some or all of the components shown in OCT console <NUM> may be included in a single unit with some or all of the components in measurement head <NUM>, for example.

The OCT console <NUM> includes multiple light sources, in the illustrated example comprising OCT laser sources 232a and 232b. OCT console <NUM> further includes a laser switch/combiner <NUM>, which allows for the selection of and/or combination of the outputs from laser sources 232a and 232b, in various embodiments. In some embodiments, laser switch/combiner <NUM> comprises an optical switch, permitting one or the other of outputs from laser sources 232a and 234b to be relayed to an OCT engine <NUM>. In other embodiments, laser switch/combiner <NUM> may comprise an optical combiner, such that laser sources 232a and 232b are selected or combined by selectively powering or lasing on laser sources 232a and/or 232b. In still other embodiments, laser switch/combiner <NUM> may combine both an optical switch and an optical combiner. It should be noted that while only two laser sources are shown in the example system <NUM> of <FIG>, other systems might include three or more distinct laser sources, with each having different optical characteristics that are useful for different OCT applications. The switching between different sources and/or operational modes may allow the switching between an optical source suitable for long-range and low-resolution imaging and a source suitable for short-range and high-resolution imaging.

OCT engine <NUM> includes an interferometer, beam splitting, reference beam length adjustment, as well as an OCT detector and digitizer. OCT engine <NUM> may further comprise a camera and frame grabber, in some embodiments. The details of interferometry for OCT are well known and not provided here, but it will be understood that OCT engine <NUM> may be configured for time-domain OCT, in which case it includes functionality for scanning the reference arm, or for spectral-domain OCT, or for swept-source OCT. In embodiments as disclosed herein, the interferometer may be configured so that it supports the use of any of several laser sources, e.g., so that the components of the interferometer are configured to handle any of several different laser wavelengths, for example.

Measurement head <NUM> includes relay optics <NUM>, scanner <NUM>, and mode-switching optics <NUM>. Scanner <NUM> comprises the circuitry and mechanics for performing x-y scanning across the imaged object (z-axis scanning is performed by OCT engine <NUM>), while relay optics <NUM> include any optical components necessary for beam deliver from the scanner to the imaged object (e.g., an imaged cornea), and more generally to couple the forward and reflected beams between the scanner and the imaged object. These may include, for example, an additional beam expander/reducer, a focusing lens, and/or lens combinations. Mode-switching optics <NUM> include one or several optical stages, where the optical components for one or more of these optical stages can be swapped out or adjusted, according to two or different operating modes, under the control of mode-switching controller <NUM>. In other words, the mode-switching optics can change/adjust the optical performance of the beam delivery path, based on the selection of one of several possible operating modes.

<FIG> shows several examples of switchable or configurable optics that might be included in mode-switching optics <NUM>. For example, mode-switching optics <NUM> may be configured so that a beam expander or beam reducer can be selected, e.g., moved in or out of an optical path, to change beam parameters for first and second operating modes. Mode-switching optics <NUM> may comprise two different collimators <NUM> with different focal lengths, for example, configured to provide different beam diameters to the input of the scanner, where mode-switching controller <NUM> selects one of the collimators according to a desired operating mode. This switching between two different collimators <NUM> is shown in <FIG>, for example, where the switching is performed with a motor <NUM>. In some embodiments, a switchable mirror <NUM> (or galvanometer mirror, MEMS mirror) can be used to change the beam direction to go through different optics; in still other embodiments, an optical fiber switch <NUM> can be used to switch between different optical paths and optics. These alternatives are shown in <FIG>. More generally, the selectable/adjustable optics in mode-switching optics <NUM> may provide for different lateral resolutions and depths of focus, for example, according to two or more different operating modes.

Referring back to <FIG>, mode-switching controller <NUM> comprises circuitry for taking as input a selection of an operating mode (e.g., from a user interface, not shown) and providing the control signals for selecting the configurable optics in mode-switching optics <NUM> and the selectable laser sources and/or source operating modes in OCT console <NUM>, e.g., via laser switcher/combiner <NUM>. Mode-switching controller <NUM> may comprise a processor circuit coupled with program memory, or digital logic, or a combination of both, and may be configured, for example, to determine a set of control signals for application to mode-switching optics <NUM> and OCT console <NUM>, based on a selected operating mode, e.g., using a look-up table or other mapping of operational mode to optics settings or control signals.

In the example embodiment shown in <FIG>, the measurement head <NUM> is attached to a surgical microscope unit <NUM>, for instrasurgical applications. <FIG> illustrates an embodiment of an OCT apparatus <NUM> in which the measurement head <NUM> is mounted on a measurement table, for clinic applications. The functionality of the various components shown in <FIG> may be identical or similar to that of the components shown in <FIG>, in some embodiments, but the optical components may vary, depending on the particular applications or range of applications for which the equipment is intended.

Similarly, <FIG> shows an embodiment of an OCT apparatus <NUM>, in which a measurement head <NUM> combines both OCT functionality as well as an aberrometer <NUM>. The aberrometer <NUM> could be based on ray-tracing, for example, in which case it may share the scanning functionality with the OCT functions. Alternatively, aberrometer <NUM> may be based on Schack Hartman or Talbot Moire technologies, for example, in which case it may be coupled into the optical path through a dichroic beam splitter.

With the above detailed examples in mind, it will be appreciated that an example optical coherence tomography (OCT) apparatus embodying one or more of the devices and techniques describe herein includes an optical source module comprising two or more selectable optical sources and further comprises an OCT engine coupled to the optical source module, the OCT engine comprising an OCT interferometer. This example OCT apparatus still further includes a mode-switching optics module coupled to the OCT engine and comprising one or more swappable, selectable, or adjustable optical components, such that the mode-switching optics module is configured to selectively provide two or more optical configurations for the optical path between the OCT engine and an imaged object, according to two or more corresponding operating modes. It should be appreciated that the term "module" is used herein to refer to an assembly of devices, such as optical devices, electronic devices, where the module may also comprise circuit boards, mounting apparatuses, housings, connectors, and the like.

In some embodiments, the OCT apparatus further includes a mode-switching controller configured to (a) control the optical source module to select an optical source and (b) control the mode-switching optics module to select one of the two or more optical configurations for the optical path, based on a selected operating mode. In some embodiments, the mode-switching controller is configured to receive, from a user interface, an indication of the selected operating mode. In some embodiments, the OCT apparatus further comprises a microscope coupled to the mode-switching optics and configured for viewing an imaged object scanned by the OCT apparatus.

In some embodiments, the optical source module comprises an optical switch configured to switch an output of a selected one of the two or more selectable optical sources, for relaying to the OCT engine. In some of these and in some other embodiments, the optical source module comprises an optical combiner configured to combine outputs from the two or more selectable optical sources, where the two or more selectable optical sources are configured to be selected by selectively powering or lasing on one of the selectable optical sources.

In some embodiments, the mode-switching optics module comprises a beam expander element or beam reducer element, where the beam expander element or beam reducer element is configured to be selectively moved in or out of the optical path, to change beam parameters for at least first and second operating modes. In some of these and in some other embodiments, the mode-switching optics module comprises first and second collimators, having different focal lengths, where the first and second selectable collimators are configured to be selectable according to a desired operating mode. In some of these latter embodiments, the mode-switching optics module comprises a switchable mirror controllable to selectively change an optical beam direction to pass through the first collimator or second collimator, depending on a selected operating mode, while in others the mode-switching optics module comprises an optical fiber switch controllable to selectively direct an optical beam through the first collimator or second collimator, depending on a selected operating mode.

<FIG> illustrates an example method suitable for implementation in an OCT apparatus, such as an OCT apparatus configured according to any of the above examples. As seen at block <NUM>, the method comprises controlling an optical source module to select one of two or more selectable optical sources. As seen at block <NUM>, the method further comprises controlling a mode-switching optics module coupled to the optical source module via an OCT engine, the OCT engine comprising an interferometer, to select one or more swappable optical components or to adjust one or more adjustable optical components, so as to select one of two or more selectable optical configurations for the optical path between the OCT engine and an imaged object.

In some embodiments, the method further comprises receiving, from a user interface, an indication of the selected operating mode, wherein said controlling of the optical source module and the mode-switching optics module is responsive to the received indication. This is shown at block <NUM>, which is illustrated with a dashed outline to indicate that it need not be present in every embodiment or instance of the illustrate method.

In some embodiments, controlling the optical source module comprises controlling an optical switch configured to switch an output of a selected one of the two or more selectable optical sources, for relaying to the OCT engine. In other embodiments, controlling the optical source module comprises selectively powering or lasing on one of the two or more selectable optical sources.

In some embodiments, controlling the mode-switching optics module comprises controlling the mode-switching optics to move a beam expander or beam reducer in or out of the optical path, to change beam parameters for at least first and second operating modes. In some of these and in some other embodiments, controlling the mode-switching optics module comprises selecting between at least first and second collimators, having different focal lengths, where the first and second selectable collimators are configured to be selectable according to a desired operating mode. In some of these latter embodiments, controlling the mode-switching optics module comprises controlling a switchable mirror to selectively change an optical beam direction to pass through the first collimator or second collimator, depending on a selected operating mode, while in others, an optical fiber switch is controlled to selectively direct an optical beam through the first collimator or second collimator, depending on a selected operating mode.

Claim 1:
An optical coherence tomography (OCT) apparatus (<NUM>, <NUM>, <NUM>), comprising:
an optical source module comprising two or more selectable optical sources (232a, 232b);
an OCT engine (<NUM>) coupled to the optical source module, the OCT engine comprising an OCT interferometer; and
a mode-switching optics (<NUM>) module coupled to the OCT engine (<NUM>) and comprising one or more swappable, selectable, or adjustable optical components, such that the mode-switching optics module is configured to selectively provide two or more optical configurations for the optical path between the OCT engine (<NUM>) and an imaged object, according to two or more corresponding operating modes,
wherein the optical source module comprises an optical switch (<NUM>) configured to switch an output of a selected one of the two or more selectable optical sources (232a, 232b), for relaying to the OCT engine,
or wherein the optical source module comprises an optical combiner (<NUM>) configured to combine outputs from the two or more selectable optical sources (232a, 232b), and wherein the two or more selectable optical sources (232a, 232b) are configured to be selected by selectively powering or lasing on only one of the selectable optical sources (232a, 232b).