Corneal Flap Cutting Patterns for Bubble Management
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Solution Overview
Problem
Femtosecond lasers used in LASIK surgeries often create excessive gas bubbles during flap cutting in the corneal stroma, leading to tissue bridges and rough bed surfaces, which interfere with the cutting process and complicate flap lift.
Innovation Solution
Implementing a method using a resonant scanning femtosecond laser with specific flap cutting patterns that include intrastromal pockets to vent gas bubbles posterior and outside the flap bed and side cuts, ensuring complete tissue separation and minimizing tissue tags and opaque bubble layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional flap cutting patterns are used, then the cutting process is simple, but gas bubbles create tissue bridges and rough bed surfaces that interfere with cutting
Solution Approach 1:
The flap cutting pattern is divided into multiple distinct components: a bed cut region, a peripheral ring cut, and multiple side cut layers at different depths. This segmentation allows each region to be optimized independently, with the ring cut specifically designed to intercept and vent gas bubbles before they can interfere with the bed cut, thereby improving cutting quality without requiring a completely complex redesign
Solution Approach 2:
The invention introduces multiple side cut layers at different depths (Z-dimension) to address the gas bubble problem. By creating side cuts at multiple depth levels rather than a single plane, the design provides additional pathways for gas bubble venting and prevents tissue bridges from forming, improving reliability while adding controlled complexity in the depth dimension
2Manufacturing precision
If laser scanning continues through bubble regions, then complete flap cutting is attempted, but bubbles block the laser beam creating uncut tissue regions
Solution Approach 1:
The peripheral ring cut is performed before the bed cut in a specific sequence. This preliminary ring cut creates a venting pathway that allows gas bubbles to escape before they can block the subsequent bed cut laser scanning. This preliminary action prevents bubble-induced interruptions and ensures complete flap cutting without reducing overall productivity
Solution Approach 2:
The ring cut acts as an intermediary structure between the external environment and the bed cut region. It provides a dedicated pathway for gas bubbles to escape to the surface, mediating the interaction between laser scanning and gas bubbles. This intermediary structure prevents bubbles from directly blocking the bed cut laser beam, ensuring manufacturing precision while maintaining cutting efficiency
3Reliability
If single-layer side cuts are used, then the cutting process is faster, but gas bubbles accumulate and create opaque layers affecting cutting quality
Solution Approach 1:
The side cut is segmented into multiple layers at different depths rather than a single continuous layer. This segmentation creates multiple venting pathways for gas bubbles at different depth levels, improving bubble management and cutting quality. The segmented approach, while adding some complexity, maintains reasonable cutting time by processing each layer efficiently
Solution Approach 2:
Different regions of the side cut are created with different local qualities - multiple discrete layers at different depths rather than a uniform single layer. This local quality variation provides targeted bubble venting pathways where needed, improving reliability without requiring a complete redesign of the entire cutting process, thus minimizing time loss
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach improves the ease of flap lift and reduces the likelihood of tissue bridges and opaque bubble layers, enhancing the precision and efficiency of the LASIK flap cutting procedure.
Implementation Method 1
Femtosecond lasers are used to cut flaps in the corneal stroma as the first step of LASIK (laser-assisted in situ keratomileusis) surgeries
Implementation Method 2
the interaction of the laser pulses with the tissue can sometimes create excessive gas bubbles which can interfere with the continued cutting of the tissue
Data Source
Figure 1A~1D
Figure 1E~2
Figure 3A~3C
AI summary
An ophthalmic surgical laser system that employs a resonant scanner, scan line rotator, and XY- and Z-scanners, the system configured for forming a corneal flap in a patient's eye with improved bubble management during each step of the flap creation process. A pocket cut is formed first below bed level, followed by the bed connected to the pocket cut, then by a side cut extending from the bed to the anterior corneal surface. The pocket cut includes a pocket region located below the bed level and a ramp region connecting the pocket region to the bed. The bed is formed by a bed cut, including multiple overlapping parallel raster scan passes, and a ring cut. The side cut is formed by multiple side-cut layers at different depths which are joined together. All cuts are formed by scanning a laser scan line generated by the resonant scanner.