What can Adaptive Optics do for Laser Photocoagulation?

Abstract

Purpose : Retinal laser photocoagulation is commonly used to treat Diabetic Macular Edema. However, it is impossible with current lasers to prevent some degree of damage to healthy neighboring tissues, which can entail a permanent degradation of visual acuity and limits the number of patients which can benefit from this treatment. This is due to the lack of control of the depth confinement of the laser, and to the eye constant motion. Adaptive Optics (AO) is a technology that corrects the eye’s aberrations in real-time, enabling laser 3D-confinement and high-resolution imaging, which can be used to precisely estimate retinal motion. Here, we evaluate how laser photocoagulation could benefit from AO in terms of 3D confinement and stabilization of the laser impact on the therapeutic target.

Methods : A 50-eye population database of high-temporal resolution characterization of ocular aberrations [Jarosz et. 2017] was used to simulate AO-corrected temporal evolution of the laser 3D-confinement in the retina for various AO-loop speeds. Retinal images stacks from 3 volunteers were acquired using PARIS’ AO flood-illumination ophthalmoscope featuring a fast AO-loop (up to 70Hz) and a high-speed sCMOS imaging camera at 200Hz. Images were acquired in several layers of the retina (with a 20µm axial step) and for various AO-loop speeds (10, 25 and 50Hz).

Results : By means of an end-to-end simulation of AO-corrected laser photocoagulation, we established the AO speed (50Hz) necessary to improve laser depth confinement from 300µm to <70µm 95% of the time. For different AO-loop speeds, both simulation and retinal imaging demonstrated that a finer laser depth confinement and imaging optical sectioning can be obtained with fast AO-loop. We also developed a real-time (latency <1ms) retinal motion estimator algorithm based on acquired images, presenting a laser stabilization precision <1µm rms, that is suitable for patients with poor fixation. Finally, we developed a method to predict effective loss of confinement or precision on stabilization due to fast changes of aberration induced by rapid eye movement, such as micro-saccades, indicating when to shut off the laser.

Conclusions : A new concept for increasing the precision of laser photocoagulation is presented. The use of high-speed (50Hz) AO-assisted laser photocoagulation leads to a better control of the laser 3D-confinement and stabilization within the therapeutic target, reducing potential surgical risks.

This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.