Liquid Loss Detection in Laser Eye Surgery Interfaces
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Solution Overview
Problem
Current laser-assisted eye surgery systems using liquid optical interfaces face challenges with liquid loss due to suction mechanisms, which can lead to air entering the interface and affecting laser optics, potentially causing harm during procedures.
Innovation Solution
Incorporation of sensors and monitoring systems within the patient interface to detect liquid levels, including conductive pads, light refraction monitoring, acoustic emitters, small orifices with vacuum detection, and gas flow meters to ensure continuous liquid presence and prevent air aspiration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If suction mechanisms are used to hold the liquid-filled interface to the eye, then the interface can be securely positioned, but liquid may be lost through the suction ports allowing air to enter the interface
Solution Approach 1:
The interface is divided into separate functional zones: a suction ring for securing the interface to the eye, and a liquid-filled chamber for optical transmission. The suction ring contains ports for applying vacuum to hold the interface, while the liquid chamber is sealed except for controlled access points. This segmentation allows independent optimization of each function without interference.
Solution Approach 2:
A liquid level sensor acts as an intermediary monitoring system that detects the presence of air bubbles or low liquid levels in the optical chamber. The sensor provides real-time feedback to the control system, which can then adjust suction pressure or alert the operator before air enters the optical path, preventing laser-optic distortion.
2Reliability
If liquid level monitoring sensors are added to detect liquid loss, then patient safety can be improved, but device complexity increases
Solution Approach 1:
Complex mechanical monitoring systems are replaced with simple optical or capacitive sensors that detect liquid level through non-contact means. For example, an optical sensor uses light refraction changes to detect air bubbles, or a capacitive sensor detects dielectric changes when liquid level drops. These electronic sensors provide reliable detection with minimal mechanical moving parts.
Solution Approach 2:
The monitoring system is integrated into the existing interface structure, using the same housing and control electronics already present in the laser system. The sensor utilizes the existing liquid chamber walls and control circuitry, eliminating the need for separate external monitoring equipment and reducing overall system complexity.
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
Prevents liquid loss detection, ensuring accurate laser delivery and patient safety by automatically shutting off the laser if liquid levels drop, maintaining a stable optical interface.
Implementation Method 1
In one embodiment, a liquid monitor includes one or more sensors positioned within the patient interface and in communication with the liquid therein
Implementation Method 2
Alternatively, a light source may be shone down onto the liquid within the patient interface and light refracted through the liquid monitored for changes in the liquid level
Implementation Method 3
Still further, a matched pair of acoustic emitter and sensor may be integrated into the patient interface which produce different signals when the liquid levels are high and low
Implementation Method 4
Another solution is to incorporate an extremely small diameter orifice in the side of the liquid chamber and pull a very low vacuum on the orifice. If the liquid is covering the orifice, surface tension will prevent aspiration of the fluid, but when the liquid level drops air can be pulled through the orifice which is detected by an external sensor in the vacuum line
Implementation Method 5
If the liquid is covering the orifice, surface tension will prevent aspiration of the fluid
Implementation Method 6
Finally, a gas flow meter may be installed within a vacuum supply circuit for a suction ring on the patient interface
Data Source
AI summary
A laser eye surgery system that has a patient interface between the eye and the laser system relying on suction to hold the interface to the eye, the patient interface using liquid used as a transmission medium for the laser. During a laser procedure sensors monitor the level of liquid within the patient interface and send a signal to control electronics if the level drops below a threshold value. The sensor may be mounted on the inside of the patient interface, within a fluid chamber. Alternatively, a gas flow meter may be added to a suction circuit for the patient interface that detects abnormal suction levels indicating low fluid level.