Ophthalmic Laser Pulse Duration for Selective Photothermal Treatment
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Solution Overview
Problem
Current ophthalmic laser treatments for retinal disorders and ocular hypertension either cause irreversible damage to surrounding tissue due to long pulse durations or are inefficient with short pulses, leading to unpredictable and costly treatments.
Innovation Solution
A system and method using light pulses or dwell times between 30 μs and 10 ms to deliver targeted photothermal treatment to ophthalmic tissues, minimizing thermal diffusion and avoiding indiscriminate damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If long pulse durations (100 ms) are used for retinal photocoagulation, then the treatment effectiveness is improved, but irreversible damage to the sensory retina and surrounding tissue occurs due to heat diffusion
Solution Approach 1:
The patent applies periodic pulsed laser action with pulse durations of 1-100 microseconds, delivering multiple pulses at controlled intervals. This periodic delivery allows thermal energy to be deposited in discrete increments, preventing continuous heat accumulation and diffusion that causes collateral damage, while still achieving cumulative therapeutic effect on the RPE.
Solution Approach 2:
The patent dynamically adjusts pulse duration within the 1-100 microsecond range and controls pulse repetition frequency to optimize thermal confinement. By making the pulse parameters dynamic rather than fixed, the system can adapt to different treatment conditions while maintaining the critical constraint that pulses remain shorter than the thermal relaxation time of the RPE.
2Object-affected harmful factors
If short pulse durations (microsecond or sub-microsecond) are used to confine heat to the RPE, then collateral damage is reduced, but photomechanical forces rupture Bruch's membrane and cause additional harm
Solution Approach 1:
The patent changes the critical parameter of pulse duration to fall within the 1-100 microsecond window, which is longer than the extremely short pulses (sub-microsecond) that cause photomechanical damage, yet shorter than the long pulses (100 ms) that cause thermal diffusion. This parameter optimization transitions the dominant mechanism from photomechanical to photothermal while maintaining thermal confinement.
Solution Approach 2:
The patent exploits the phase transition of water (boiling point) within the RPE cells during laser irradiation. The confined photothermal energy raises intracellular temperature to induce vapor bubble formation, creating mechanical disruption of pigmented organelles that triggers wound healing responses without requiring external photomechanical forces that would damage Bruch's membrane.
3Manufacturing precision
If sub-microsecond pulses are used to target melanosomes specifically, then sub-cellular precision is improved, but the therapeutic window narrows and requires complex diagnostic devices
Solution Approach 1:
The patent applies partial action by targeting only the pigmented organelles (melanosomes) within the RPE cells rather than requiring complete destruction of entire cells or sub-cellular structures. The 1-100 microsecond pulses deliver sufficient energy to heat and vaporize water within melanosomes, creating localized damage that triggers wound healing without requiring the extreme precision and complex monitoring needed for sub-microsecond pulses.
4Use of energy by moving object
If visible laser light is used for photocoagulation, then absorption by melanin in the RPE is maximized, but heat diffusion during long exposures damages the overlying sensory retina
Solution Approach 1:
The patent uses periodic pulsed delivery of visible laser light at 1-100 microsecond intervals, allowing the RPE to absorb energy efficiently during each pulse while the inter-pulse intervals prevent heat accumulation and diffusion to the sensory retina. This periodic action maintains high melanin absorption efficiency while avoiding the continuous heating that causes retinal damage.
Solution Approach 2:
The patent dynamically controls pulse duration within the 1-100 microsecond range to optimize the balance between energy absorption by melanin and thermal confinement. By making pulse duration a dynamic parameter rather than fixed, the system can adjust to different treatment conditions while ensuring pulses remain shorter than the thermal relaxation time, preventing heat diffusion to adjacent structures.
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 achieves spatially selective photothermal damage confined to specific tissue layers, reducing collateral damage and improving clinical outcomes without the need for complex diagnostic devices or expensive equipment.
Implementation Method 1
Generation of heat due to absorption of visible laser light occurs predominantly in the retinal pigmented epithelium (RPE) and pigmented choriocappilaris
Implementation Method 2
Laser photomedicine is a well-established therapeutic modality for a wide variety of conditions
Implementation Method 3
Due to heat diffusion during long exposures, this standard therapy also irreversibly damages the overlying sensory retina
Data Source
AI summary
A system and method for treating ophthalmic target tissue in which a light source generates a beam of light, a scanner unit deflects the beam of light into a pattern, a beam delivery unit for delivering the pattern to ophthalmic target tissue. The light is either pulsed or moved across the target tissue such that the light pulses having a duration of, or the light dwells on any given point of target tissue for, between 30 μs and 10 ms.