Laser Pulse Alignment for Refractive Eye Surgery
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Solution Overview
Problem
Conventional laser cutting systems for eye surgery face challenges in accurately aligning pulse firing patterns with eye features, particularly the pupil center, due to corneal deformation caused by contact with patient adapters, which hinders precise incision placement and can result in further visual defects.
Innovation Solution
A method and apparatus that determine the position of a reference feature, such as the pupil center, relative to a given corneal point in both undeformed and deformed states using imaging technologies like Scheimpflug tomography and optical coherence tomography, allowing for alignment of the pulse firing pattern in the laser device's coordinate system, even when the eye is coupled to a patient adapter, ensuring precise alignment for refractive corrections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the eye is pressed against the contact element of the patient adapter to immobilize the eye, then the eye is stabilized for laser treatment, but the cornea undergoes deformation which hinders accurate alignment of the pulse firing pattern with eye features
Solution Approach 1:
The system performs preliminary imaging and registration of eye features (pupil center, iris structure, limbus) in the undeformed state before the eye is pressed against the contact element. The pulse firing pattern is pre-calculated and registered based on these pre-deformation measurements. When the eye is deformed during surgery, the system compensates by applying transformation matrices that account for the expected corneal deformation, thereby maintaining alignment precision despite the corneal shape change.
Solution Approach 2:
The system changes the reference state parameter from the deformed state (during surgery) to the undeformed state (pre-surgery). By registering eye features and calculating the pulse firing pattern based on the undeformed corneal geometry, the system eliminates the alignment error introduced by corneal deformation. The coordinate system transformation compensates for the parameter change in corneal shape between pre-surgery and during-surgery states.
2Ease of operation
If imaging is performed after the eye is coupled to the patient adapter in the deformed state, then the eye features can be located during surgery, but the pulse firing pattern cannot be accurately aligned with the undeformed eye geometry
Solution Approach 1:
The system performs all critical imaging and registration operations before the eye is deformed by the patient adapter. The pupil center, iris structure, and limbus are imaged and registered in the undeformed state. The pulse firing pattern is calculated and stored based on these pre-deformation measurements. During surgery, the pre-calculated pattern is applied with coordinate transformation to account for corneal deformation, eliminating the need for post-deformation imaging for alignment purposes.
Solution Approach 2:
The system creates a digital copy or model of the eye's undeformed geometry through pre-surgery imaging. This virtual model includes the registered positions of eye features and the calculated pulse firing pattern. During surgery, this digital copy is used as the reference framework, and coordinate transformations are applied to map the pre-surgery pattern to the deformed surgical state, effectively using a copy of the original geometry to guide the actual cutting process.
Data Source
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AI summary
According to certain embodiments, a method for laser cutting treatment of a human eye comprises: determining position information of a pupil center of the eye in relation to a point of minimal corneal thickness in an undeformed state of the eye; locating the point of minimal corneal thickness in a flattened state of the eye, in which the eye is deformed by contact with a patient adapter of a laser device; and aligning a pulse firing pattern for laser radiation pulses of the laser device, based on a position of the located point of minimal corneal thickness and the determined position information. In embodiments, the pulse firing pattern represents, for example, a lenticular or doughnut-shaped intracorneal tissue volume which is to be removed from the cornea of the eye.