Light-adjustable lens illumination system with fovea protection

A light adjustable lens illumination system comprises an illumination source, for generating a light beam; a light delivery system, for projecting the light beam onto a Light Adjustable Lens (LAL), implanted into an eye, wherein a fraction of the light beam propagates past the LAL to a retina of the eye; and a protective beam-shaper, for shaping the light beam to have an intensity pattern with a relative central intensity reduction that varies along an axis; wherein the relative central intensity reduction at the retina is greater than the relative central intensity reduction at a LAL plane.

TECHNICAL FIELD

This patent document describes illumination systems for light adjustable lenses, and in more detail, illumination systems with fovea protection.

BACKGROUND

The techniques of cataract surgery are progressing at an impressive pace. Generations of phacoemulsification platforms and more recently introduced surgical lasers keep increasing the precision of the placement of intraocular lenses (IOLs) and keep reducing unintended medical outcomes. Nevertheless, after the IOLs have been implanted, the postsurgical healing process can shift or tilt the IOLs in a notable fraction of the patients, leading to a diminished visual acuity, and a deviation from the planned surgical outcome.

A new technique has been developed recently to correct or mitigate such a postsurgical IOL shift or tilt. The new technique is capable of adjusting the optical properties of the IOLs with a postsurgical procedure to compensate the shift or tilt of the IOL. As described in commonly owned U.S. Pat. No. 6,905,641, to Platt et al, entitled: “Delivery system for post-operative power adjustment of adjustable lens”, hereby incorporated by reference in its entirety, the IOLs can be fabricated from a photo-polymerizable material, henceforth making them Light Adjustable Lenses, or LALs. In the days after the surgery, the implanted LALs may shift and tilt, eventually settling into a postsurgical position different from what the surgeon planned. Once the LAL settled, a Light Delivery Device (LDD) can be used to illuminate the LALs with a UV light having an illumination pattern that induces photopolymerization of the macromers in the LAL with a corresponding spatial pattern, thus changing the refractive optical properties of the LALs. This refractive change adjusts the LAL optical performance to compensate the unintended postsurgical shift or tilt of the LAL. Once the optical characteristics of the implanted LAL is achieved by the light-induced photopolymerization, a final “lock-in” illumination can be applied to photopolymerize the remaining macromers in a manner that does not further change the optical properties of the LAL. The LAL technology enables the physician to adjust the optical characteristic of the implanted LAL post-surgically and non-invasively, and thus promises to greatly improve the medical outcome of cataract surgery and thus patient satisfaction.

While present day LDDs are safe, it is still prudent to further enhance the safety of this promising LAL technology. One of the motivations is that the illumination is performed with a UV light, for which the human retina is particularly sensitive. The part of the retina with the highest UV-light sensitivity is the fovea, a small central region where most of the color-sensing cones are located. Therefore, there is a need for Light Delivery Devices that provide additional protection for the fovea.

SUMMARY

Embodiments address the above medical needs as follows. Some embodiments of a light adjustable lens illumination system comprise an illumination source, for generating a light beam; a light delivery system, for projecting the light beam onto a Light Adjustable Lens (LAL), implanted into an eye, wherein a fraction of the light beam propagates past the LAL to a retina of the eye; and a protective beam-shaper, for shaping the light beam to have an intensity pattern with a relative central intensity reduction that varies along an axis; wherein the relative central intensity reduction at the retina is greater than the relative central intensity reduction at a LAL plane.

DETAILED DESCRIPTION

FIGS. 1-3illustrate the previously discussed medical need in some detail.FIGS. 4-8illustrate embodiments that provide solutions for this medical need.

FIG. 1shows a Light Adjustable Lens (LAL) illumination system100that generates a light beam115and propagates, or delivers, the light beam115into an eye1. The eye1includes an annular iris5that defines a central opening, a pupil10. The iris5is typically dilated for the illumination procedure, as indicated. The incoming light beam115enters the eye through a cornea15and propagates through the pupil10along an axis20. The light beam115propagates through a vitreous22and eventually reaches a retina25at a posterior end of the eye1. Two features of this posterior end are mentioned here expressly and illustrated inFIG. 2. First, an optical nerve30collects and transmits the visual stimuli from the retina25and transmits them towards the brain. The spot where the optic nerve30leaves the eye1has practically no light-sensing cells, known as rods and cones, and is hence often called a blind spot. The other feature of note is a fovea35, where a density of color-sensing cones has a sharp, narrow peak. These cones are particularly sensitive to light.FIG. 2illustrates how sharply localized this peak is: a typical fovea35has a radius of about 1.5 mm.

The light beam115is directed by the LAL illumination system100at a LAL50, implanted in the eye1and stabilized in place by haptics55in a capsular bag, from which the natural cataractous crystalline lens of the eye has been removed. For some classes of LALs, this illumination light can be a UV light beam with sufficient intensity to adjust the optical properties of the LAL50by photopolymerization. There are various ways to protect the retina25from the undesirable effects of this intense UV light. First, the composition of the LAL50includes light-absorbing components, such as dispersed UV absorber molecules. Second, a UV-blocking back-layer can be also formed at a posterior surface of the LAL50. The UV absorbers dispersed in the volume of the LAL50, and disposed in its back-layer greatly reduce the intensity of the illumination light as it propagates across the LAL50, so that only a very small portion of the incident light beam115manages to get through the LAL50and continue to propagate across the vitreous22to the retina25. Some LALs allow less than 1% of the incoming UV light to pass through. Others allow less than 0.1% of the light to pass through. Nevertheless, it is prudent to further enhance the retinal safety by implementing additional protections, especially for the retina's most sensitive area, the fovea35.

FIGS. 3A-Billustrate a second motivation to enhance the protection of the retina25and especially the fovea35. When the illumination beam115is directed into the eye1, the light beam115needs to be aligned with the LAL50. Here the term aligned is short for aligning the axis20of the light beam115with an optical axis of the LAL50, and centering the light beam115to the center of the LAL50. The physician, or ophthalmologist who performs the procedure, is sometimes advised to place a contact lens70onto the cornea15, and manually manipulate the contact lens70, and thus the eye1, so that the light beam115is aligned with the LAL50. In spite of the best intentions of the physician, the effort to align the light beam115and the LAL50, and to keep them aligned, may not be fully successful. An involuntary eye movement, a head movement, a sneezing, an alarmed patient reaction can all cause such misalignment, at least for a short time.FIG. 3Bshows that in such cases, the light beam115can bypass the LAL50at least in a small region, as a bypassing light beam115b. For these short and fractional misalignments, the volumetric and back-layer UV absorbers of the LAL50will not reduce the intensity of the bypassing light beam115b. The UV bypassing light beam115bimpacting the retina25in general and its most sensitive region, the fovea35, in particular, can lead to undesirable medical outcomes. This is a second reason to develop and implement additional protective technologies in the LAL illumination system100.

FIG. 4illustrates a LAL illumination system100that includes such protective technologies. The LAL illumination system100can include an illumination source110, for generating the light beam115; a light delivery system120, for projecting the light beam115onto a Light Adjustable Lens (LAL)50, implanted into an eye1, so that a fraction of the light beam115propagates past the LAL50to a retina25of the eye1; and a protective beam-shaper200, for shaping the light beam115to have an intensity pattern201with a relative central intensity reduction that varies along an axis20; wherein the relative central intensity reduction at the retina25is greater than the relative central intensity reduction at a LAL plane.

This beam-shaping is innovative, as it simultaneously satisfies competing and seemingly contradictory requirements. The protective beam-shaper200is designed to greatly reduce a central intensity of the light beam115at the retina25to protect the fovea35, while reducing the central intensity of the light beam115only moderately at the LAL plane, so that the optical characteristics of the LAL50are not modified by the shaped intensity pattern of the light beam115.

The protective beam shaper200can be part of the light delivery system120, as shown. In other embodiments, it can be a self-standing block, or part of the illumination source110, as indicated by the dashed line.

Examples of the discussed intensity patterns are illustrated in the right panel ofFIG. 4. The intensity of the light beam115can have the following radially varying intensity pattern201at a specific axial coordinate z. Approaching from outer distances r from the center, the intensity is rising with decreasing distance r, as it is typical for ordinary beams, like Gaussian beams. The intensity pattern201, however, reaches a maximum A, and with further decreasing r, the intensity starts dropping towards a reduced beam center intensity C, at r=0, by a reduction R=A−C. This dependence of the intensity pattern201of the radial distance r is shown in the lower right panel ofFIG. 4. The arguments of A(z), C(z) and R(z) indicate the axial (z) coordinate along the axis20of the intensity pattern201: A(LAL), C(LAL) and R(LAL) denote the maximum A, the reduced beam center intensity C, and the reduction R at the z axial coordinate where a plane of the LAL50intersects the axis20, whereas A(ret), C(ret) and R(ret) denote the same at the retina.

With this preparation, the described relative central intensity reduction of the intensity pattern201, denoted by Δ, can be thought of as a ratio of the maximum intensity A minus the reduced beam center intensity C, i.e. A−C=R, divided by the maximum intensity A: Δ=(A−C)/A=R/A. With this definition, the protective beam-shaper200shaping the light beam115to have the above intensity patterns201at the LAL plane and at the retina can be captured in Eq. (1) as follows:

FIG. 5Aillustrates that the reduction of the beam center intensity can have an extended minimum, such as a flat minimum over a central region202, where an irradiance of the intensity pattern is approximately flat. The protective beam-shaper200can be configured to shape the light beam115so that this central region202of the illumination pattern201at the retina25is positioned to include the fovea35of the eye1. With such a beam-shaping, the protective beam-shaper200can provide a solution for the medical need of the LAL illumination system100, described in the opening remarks: to protect the fovea35by substantially reducing the intensity of the light beam115that impacts the fovea35.

FIG. 5Ashows, a typical intensity pattern201as shaped by the protective beam-shaper200. The intensity can be measured, e.g., in terms of an irradiance, with units of power over area, in the present case, mW/cm2. The intensity pattern201of the light beam115at the retina25can be called a protective intensity pattern201p, if the reduced beam center intensity C(ret) in the central region202is less than a threshold to fully protect the fovea35. In some embodiments, this protection threshold is the reduced beam center intensity C(ret) being less than 0.1 mW/cm2. In other embodiments, the protective intensity pattern201pcan have a reduced beam center intensity C(ret) less than 1 mW/cm2, in yet others, less than 0.01 mW/cm2. For comparison, the intensity pattern201is also shown when the protective beam-shaper200is removed from the LAL illumination system100. Visibly, this intensity pattern201has no reduction at the center, and thus is not a protective intensity pattern201p.

To place these irradiance values in the context of the light adjustable lens technology, the illumination source110typically generates a light beam115with a wavelength in a range of 300 nm-450 nm, often in the range of 350 nm-400 nm, making the light beam115a UV beam. This UV light beam115is directed onto the LAL50to photopolymerize macromers in a spatial adjustment pattern corresponding to the adjustment intensity pattern of the light beam115, which is formed to adjust the optical properties of the LAL50. In typical cases, once the desired adjustment of the optical properties has been achieved, the LAL50still contains remaining photopolymerizable macromers in a certain concentration. Subsequent uncontrolled, or uneven photopolymerization of these remaining macromers could change the refractive properties of the LAL50away from the values intended by the physician. To prevent such undesirable developments, all remaining photopolymerizable macromers are neutralized in a subsequent lock-in process. In this lock-in process, the illumination source110applies a lock-in light beam115to the LAL50to photopolymerize all remaining macromers in a manner that does not further adjust the optical properties of the LAL50. This step thus “locks in” the previous light adjustment of the LAL50. To make sure that essentially no photopolymerizable macromers are left behind that could alter the previously induced optical adjustment, the intensity of the light beam115of the lock-in illumination is chosen to be sufficiently high. Light beam intensities during the lock-in illumination can reach 100-1,000 mW/cm2, in others 200-400 mW/cm2, with corresponding energy densities of 10-100 J/cm2, in others, 20-40 J/cm2. The correspondence is further impacted by the procedure time, which can be 10-150 sec, in some cases 60-100 sec. All quantities are referenced at the plane of the LAL50. Moreover, the lock-in illumination in some cases can have a radial pattern, where a peak-to-edge ratio can be in the range of 1.5-10, in other cases 2-5. Therefore, the protection of the fovea35is the most pressing during the lock-in illumination. In some embodiments of the LAL illumination system100, the protective beam-shaper200can create a protective intensity pattern201pwith a central intensity C(ret) less than the above recited limits of 1 mW/cm2, 0.1 mW/cm2, or 0.01 mW/cm2, even during a lock-in illumination that have the just described high intensities.

FIG. 5Ashows that the definition of the central region202may involve some ambiguity. For an intensity pattern201with a flat region in the center, the flat region may be called the central region202. For round intensity patterns without a flat region in the center, the diameter of central region202′ can be defined where the irradiance got reduced to 50% of its value at its maximum at A, as shown. Other, analogous definitions of the central region202can be also adopted, for example, with reduction to 30%, or 20%, of the maximum. With this context, in some embodiments, a diameter of the central region202can be less than 2.5 mm, 2 mm, or 1.5 mm. Here it is recalled that a typical diameter of the fovea35is about 1.5 mm, thus the above listed diameters of the central region202are suitable to provide full foveal protection.

FIG. 5Bshows the protective intensity pattern201pofFIG. 5Aas a heat map, over a retinal plane. Lighter colors indicate higher irradiance. In the graphs ofFIGS. 5A-B, visibly the intensity reduction is essentially complete, and thus C(ret) is approximately zero, R(ret) is approximately equal to A(ret), and therefore the relative central intensity reduction of this protective intensity pattern201p, Δ(ret), is approximately 1.

FIG. 5Cillustrates that the protective beam shaper200can shape the light beam115to offer a solution for the other medical need described earlier: the mitigation of the retinal impact of a potentially bypassing light beam115bin case of a misalignment between the light beam115and the LAL50. Four curves show the irradiance of the protective intensity pattern201pfor light beams whose axis20is misaligned from a center of the LAL50by 0 mm (aligned), 0.15 mm, 0.30 mm, and 0.45 mm. Visibly, for the first three misalignment values of 0-0.30 mm, C(ret) remains essentially zero, and thus the fovea35remains fully protected. Even for the largest misalignment of 0.45 mm, while a small fraction of the misaligned bypassing light beam115breaches the retina25, it does so only far away from the fovea35. The reduction R(ret) of the intensity pattern at the fovea35(at the center) remains essentially complete, and the relative central intensity reduction of the protective intensity pattern201p, Δ(ret), remains approximately 1.

The relative central intensity reduction at the retina, Δ(ret), can be greater than the relative central intensity reduction at the LAL, Δ(LAL), in different manners. In some embodiments, the relative central intensity reduction at the retina, Δ(ret), can be greater than 30%, while the relative central intensity reduction at the LAL plane, Δ(LAL), can be less than 30%. In other embodiments, the relative central intensity reduction at the retina, Δ(ret), can be greater than 50%, while the relative central intensity reduction at the LAL plane, Δ(LAL), can be less than 20%.

FIGS. 6-8illustrate various specific embodiments210-240of the protective beam-shaper200. In general terms, these protective beam-shaper200embodiments can shape the light beam115by blocking, absorption, attenuated transmission, modulation, or reflection. In yet other embodiments, they can shape the generation of the light beam115itself.

FIG. 6shows an embodiment where the protective beam-shaper200is part of the light delivery system120and includes a beam-stopping obscuration disk210. This obscuration disk210can be positioned at an optical conjugate plane of the retina25of the eye1, or retina conjugate plane212-1for short. The obscuration disk210can be precisely at this retina conjugate plane212-1, or can be close to it, within a reasonable tolerance. Referencing well-known optical considerations of conjugate planes, the light delivery system120images the obscuration disk210positioned at the retina conjugate plane212-1sharply onto the retina25. Objects positioned away from the retina conjugate plane212-1are not imaged sharply onto the retina25, instead, they only form a blurry pattern on the retina25.

Embodiments of the LAL illumination system100can include a beam modulator to modulate an intensity of the light beam115to create the earlier described adjustment intensity pattern. The beam modulator (not shown) can be positioned at a LAL conjugate plane214-1. In some embodiments, the beam modulator230can include a digital mirror device with an actuatable micro-mirror-array, to receive the light beam115generated by the illumination source110, and to reflect the received light beam115according to the adjustment intensity pattern. In some cases, this digital mirror device can redirect the light beam115. The field of digital mirror devices is mature, and many solutions have been developed and are used, for example, in projectors and presenting devices. Any of these digital mirror devices can be used as the beam modulator, as well as non-mirror-based beam modulators.

The obscuration disk210is configured to stop a central portion of the light beam115, thereby generating a centrally obscured intensity pattern215, such that the relative central intensity reduction at the retina25, Δ(ret), is greater than the relative central intensity reduction at the LAL plane, Δ(LAL). The far-right panel ofFIG. 6shows that the obscuration disk210stopping a central portion of the light beam115at the retina conjugate plane212-1that images sharply onto the retina25creates an intensity pattern201on the retina25that is a protective intensity pattern201in that the intensity in its central region202is reduced to essentially zero, making C(ret)≈0 and Δ(ret)≈1.

As shown inFIG. 6, there can be more than one retina conjugate planes, such as retina conjugate plane212-2, depending on the complexity of the light delivery system120. The obscuration disk210can be positioned into any of these retina conjugate planes212-1or212-2. For orientation, the LAL conjugate plane214-1is also shown. Objects positioned at this LAL conjugate plane214-1are imaged onto the LAL plane. Various embodiments of the light delivery system120can have a wide variety of optical solutions, beyond the shown simple pairs of collimating lenses proximal and distal to the obscuration disk210, and a distal focusing objective122. Also, the obscuration disk210can be part of a beam aperture. Finally, the obscuration disk210can be more than a simple hard beam stop. For example, it can have an annulus whose transparency is increasing with increasing radius.

FIG. 7illustrates another embodiment, where the protective beam-shaper200is again part of the light delivery system120, but now operates in a transmission mode, and includes a beam-attenuator220, to transmit the light beam115with an attenuated intensity pattern225, such that the relative central intensity reduction at the retina25, Δ(ret), is greater than the relative central intensity reduction at the LAL plane, Δ(LAL). As before, this beam attenuator220can be positioned at the retina conjugate plane212-1. The beam attenuator220can include an LCD array that is operated in a transmission mode. The beam attenuator220can induce an attenuated intensity pattern225by gradually changing the transmission coefficient of the LCD array. As such, the intensity pattern201at the retina25can again be a protective intensity pattern201p, while the variation of the intensity can be more gradual, as shown in the right panel ofFIG. 7.

FIG. 8illustrates that in some embodiments, the protective beam-shaper200and the illumination source110can be integrated into an annular illumination source240, configured to generate the light beam115with an annular intensity pattern245, such that the relative central intensity reduction at the retina25, Δ(ret), is greater than the relative central intensity reduction at the LAL plane, Δ(LAL). The annular illumination source240can be positioned at the retina conjugate plane212-2, and can generate a protective intensity pattern201pon the retina25.

While this document contains many specifics, details and numerical ranges, these should not be construed as limitations of the scope of the invention and of the claims, but, rather, as descriptions of features specific to particular embodiments of the invention. Certain features that are described in this document in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments separately or in any suitable subcombination. Moreover, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to another subcombination or a variation of a subcombinations.