Real time acoustic dosimetry for corneal collagen crosslinking
Inventors
Lopath, Patrick David • Acker, David E.
Assignees
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Publication Number
US-9883970-B2
Publication Date
2018-02-06
Expiration Date
Abstract
A change in the response of the cornea to ultrasonic energy directed into the cornea is monitored during irradiation of the cornea to bring about corneal crosslinking. Because the change in ultrasonic response is correlated with the degree of crosslinking achieved, a desired degree of crosslinking can be achieved by terminating the irradiation when the change reaches a threshold. The change in ultrasonic response can be determined by taking a baseline measurement before irradiation and additional measurements during irradiation using the same ultrasonic transducer (47). The transducers may be carried on a device (30) resembling a contact lens which overlies the eye and which transmits the light used in the irradiation step to the eye.
Core Innovation
The invention provides a system for corneal crosslinking that uses a light source, a structure adapted to rest on an anterior surface of an eye, and one or more ultrasonic transducers carried on the structure. The structure is adapted to transmit light from the source to the cornea, while the transducers are actuated by a drive circuit to direct ultrasonic energy into the cornea and to derive signals representing ultrasonic energy returned from the cornea.
A control circuit repeatedly determines a response of the cornea based on the returned ultrasonic signals, provides a baseline response before operation of the light source to irradiate the cornea, and determines one or more additional responses during operation of the light source. The control circuit compares the additional responses to the baseline response and controls operation of the light source based at least in part on the results of the comparison.
The disclosed ultrasonic measurement approaches represent corneal response by ultrasound transmission time using anterior and posterior echoes and arrival-time delay, by natural vibration frequency or period derived from an excitation and monitoring sequence, or by a backscattered ultrasound spectrum as a proxy for crosslinking degree. The disclosed on-eye structure has a contact-lens-like form factor and can include a light diffuser and an acoustic matching diffuser with a backing layer to facilitate coupling of ultrasound.
The comparison results are used to change control operation of the light source, including terminating irradiation when a threshold change is reached, optionally with a threshold tied to the baseline response. Dependent disclosures also include using a two-dimensional ultrasonic array for controlling multiple corneal regions and mention compensating for intraocular pressure using a composite proxy.
Claims Coverage
The provided claims cover an integrated on-eye corneal crosslinking system with repeated baseline-versus-additional response comparison and control of the light source, together with specific response representations and structural limitations. The inventive features include threshold-based termination, natural vibration frequency or period, echo-based transmission time, and a contact-lens-shaped structure.
Corneal crosslinking system with light source and on-eye light-transmitting structure
A system includes a light source and a structure adapted to rest on an anterior surface of an eye of the subject, the structure being adapted to transmit light from the source to the cornea.
On-structure ultrasonic transducers for ultrasonic energy and returned-energy signals
One or more ultrasonic transducers are carried on the structure, and the drive circuit actuates the transducers to direct ultrasonic energy into the cornea and derive signals representing ultrasonic energy returned from the cornea.
Repeated baseline and additional response determination using returned ultrasonic signals
A control circuit repeatedly determines a response of the cornea to the ultrasonic energy based on the signals to provide a baseline response before operation of the light source to irradiate the cornea and one or more additional responses during the operation of the light source.
Comparison of additional responses to baseline to control light-source operation
The control circuit compares the additional responses to the baseline response and controls operation of the light source based at least in part on the results of the comparison.
Terminate irradiation based on compared response change exceeding a threshold
The control circuit determines a change in the response based on the comparison and controls termination of the irradiation when the response change exceeds a predetermined threshold.
Natural vibration frequency or period derived from excitation and monitoring ultrasonic energy
The system actuates ultrasonic transducers to deform the cornea with an excitation pulse, applies monitoring ultrasonic energy, detects reflected monitoring energy, and determines a natural vibration frequency or period of the cornea from resulting signals.
Ultrasound transmission time determined from anterior and posterior echo signals
The system actuates ultrasonic transducers to send brief ultrasonic pulses into the cornea, detects echoes from the cornea's anterior and posterior surfaces to generate corresponding signals, and determines an ultrasound transmission time through the cornea based at least in part on those echo signals.
Transmission time determined using delays between anterior and posterior echo signals
A control circuit determines transmission time for pulses and echoes through the cornea based at least in part on delays between signals representing echoes from the cornea's anterior and posterior surfaces.
Contact-lens-shaped light-transmitting structure
The structure is configured to have the size and shape of a contact lens.
Across the provided claims, the core claim defines an integrated on-eye corneal crosslinking system that repeatedly determines baseline and additional corneal responses from returned ultrasonic signals, compares them, and controls the light source based on the comparison. The dependent claims add specific inventive implementations for the corneal response representation and decision logic, including threshold-based termination, derivation of natural vibration frequency or period, and echo-derived ultrasound transmission time, as well as a contact-lens-shaped structure.
Stated Advantages
Provides control of light-source operation based at least in part on a comparison between additional corneal responses and a baseline response.
Enables terminating irradiation when a response change exceeds a predetermined threshold.
Uses ultrasonic measurement modalities that correlate with degree of crosslinking, using responses derived from baseline versus additional measurements.
Claims that using the same transducer reduces systematic errors.
Documented Applications
Real-time acoustic dosimetry for corneal collagen crosslinking (CCXL) using an on-eye device during irradiation.
Monitoring and controlling corneal crosslinking using ultrasonic measurement of corneal response represented by ultrasound transmission time, natural vibration frequency/period, or backscattered ultrasound spectrum as a proxy.
Controlling multiple corneal regions with a 2D ultrasonic array.
Compensating for intraocular pressure using a composite proxy.
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