Abstract
Purpose :
Selectively damaging a fraction of RPE cells in aged eyes using short-pulse laser could provide benefits associated with RPE rejuvenation. However, variation in pigmentation within the eye and between different subjects results in inconsistent damage threshold. We propose a titration-based method to determine the therapeutic window prior to treatment. This approach could enable patient-specific laser parameters for targeting RPE without damaging photoreceptors.
Methods :
A Pascal Synthesis 577nm laser was used to induce RPE damage in pigmented rabbits (Dutch Belted). Titration was performed in the treatment area by adjusting the laser power to produce a barely visible retinal lesion with a 200 μm diameter spot and 20 ms pulse duration. The line scanning treatment was delivered using 100 μm diameter spot, along 2mm length, at 6 m/s velocity, with 3 repeats applied at 10 Hz, within power range of 0.6-2 W. The RPE and photoreceptor damage were evaluated at days 0 (D0), 1 (D1) and 7 (D7) after treatment using OCT, fluorescein angiography (FA) and scanning electron microscopy (SEM). The RPE and photoreceptor damage thresholds were plotted against the titration damage thresholds to produce an algorithm predicting the appropriate laser power to use.
Results :
RPE damage was observed by the increase in fluorescein intensity with increasing power right after treatment. 1 day after laser, fluorescein leakage from the choroidal circulation was still visible, but had completely subsided by day 7, indicating a recovery of the outer blood retinal barrier. RPE damage was confirmed on SEM by an absence of RPE cells within the line scan area at D1, exposing the Bruch’s membrane. The RPE cells had repopulated the lasered area by D7. OCT imaging revealed the laser powers that induced photoreceptor loss. The titration damage thresholds were correlated with the RPE and photoreceptor damage thresholds and a titration algorithm was derived.
Conclusions :
The rejuvenation of RPE based on migration and proliferation of cells observed after line scanning treatment could be used for treatment of diseases associated with RPE dysfunction. The titration algorithm provides a predictable and patient-specific laser dosimetry, targeting RPE cells without causing damage to the overlaying photoreceptor cells.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.