Corneal measurement and control of corneal crosslinking
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Publication Number
US-11020608-B2
Publication Date
2021-06-01
Expiration Date
Abstract
Systems and methods for monitoring properties of the cornea and controlling the crosslinking treatment. The thickness of the cornea during crosslinking may be measured by using ultrasonic reflections to determine an anterior distance (D1′) between a reference location (37) on a device resting on the eye and an anterior surface (66) of the cornea and to determine a posterior distance (D3′) between a posterior surface (63) of the cornea and an element of the eye such as an anterior surface (72) of the lens of the eye. These distances are subtracted from a reference distance (D0) between the reference location and the element of the eye. The reference distance (D0) may be determined using ultrasonic reflections to determine the corresponding anterior and posterior distances and the thickness (D2) of the cornea prior to crosslinking. The speed of sound in the cornea during crosslinking may be derived using the thickness (D2′) and time of flight of ultrasound through the cornea. The position of the cornea relative to a reference location may be determined. In still other embodiments, location of a surface of demarcation (86) within the cornea formed as a result of crosslinking may be determined. Still other embodiments provide for determination of one or more resonant frequencies of the cornea, and for measurement of responses of the cornea to applied forces, such as displacement and rebound velocity. The properties of the cornea may be used as proxies for the extent of crosslinking, and a light source (48, 348) used to induce crosslinking may be controlled in response to such proxies.
Core Innovation
The invention provides a corneal crosslinking system that controls irradiation of a cornea by repeatedly applying monitoring ultrasonic energy and deriving signals representing ultrasonic energy returned from the cornea. A control circuit determines a position of a structure of the cornea relative to a reference location by determining a time of flight of the monitoring ultrasonic between the reference location and the structure. Baseline position(s) are established before operation of the light source and one or more additional positions are determined during operation of the light source.
The reference location is selected from an element of a device resting on the eye and an element of the eye posterior to the cornea. The control circuit compares the additional positions to the baseline position and controls operation of the light source based at least in part on the results of the comparison. In related embodiments, anterior and posterior distances are measured by anterior and posterior time of flight measurements, and corneal thickness is yielded by subtraction from a reference distance.
Further embodiments derive corneal speed of sound from ultrasonic time of flight and measured thickness, and control the light source based at least in part on the computed speed of sound. Additional embodiments determine a location of a surface of demarcation formed within stroma in response to the irradiation by using ultrasonic measurements, and control the light source based at least in part on the determined location of the surface of demarcation.
Claims Coverage
Independent claims are recited in three independent claim sets. Across these, the claims cover repeated monitoring ultrasonic pulses with returned-signal processing, baseline-to-additional position comparison or derived thickness/speed-of-sound, and controlling the light source based on measured corneal structural information.
Position determination using monitoring ultrasonic time of flight with baseline comparison
A control circuit repeatedly determines a position of a structure of the cornea relative to a reference location by determining a time of flight of the monitoring ultrasonic between the reference location and the structure of the cornea based on signals, to provide a baseline position before operation of the light source to irradiate the cornea and one or more additional positions during operation; the control circuit compares the additional positions to the baseline position and controls operation of the light source based at least in part on the results of the comparison.
Anterior and posterior ultrasound time-of-flight to yield corneal thickness
A control circuit determines an anterior distance by measuring an anterior time of flight for ultrasound between an element of the device and an anterior surface of a corneal structure; determines a posterior distance by measuring a posterior time of flight for ultrasound between an element of the eye posterior to the corneal structure and a posterior surface of the corneal structure; and subtracts the anterior and posterior distances from a reference distance between the element of the device and the element of the eye to yield the thickness of the corneal structure.
Demarcation surface location in stroma and light-source control
A control circuit determines from the signals a location of a surface of demarcation formed within stroma of the cornea formed by crosslinking responsive to irradiation by the light source, and controls the operation of the light source based at least in part on the determined location of the surface of demarcation.
Overall, the claim set covers corneal crosslinking systems that use monitoring ultrasound time-of-flight and returned ultrasonic signals to determine corneal structural positions relative to a reference and compare baseline to additional positions for light-source control, measure anterior and posterior time-of-flight distances to compute corneal thickness, and determine the location of a stromal demarcation surface and control the light source based on that location.
Stated Advantages
Not explicitly described in patent.
Documented Applications
Not explicitly described in patent.
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