Purchase this article with an account.
Katharina Bliedtner, Denise Meier, Eric Seifert, Ralf Brinkmann; Towards feedback controlled selective laser trabeculoplasty (SLT). Invest. Ophthalmol. Vis. Sci. 2018;59(9):6094.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Selective Laser Trabeculoplasty (SLT) is widely used as a treatment option for open-angle glaucoma, however, it lacks an instant evidence for successful irradiation. So far ophthalmologists use the visible appearance of permanent macro bubbles (champagne like bubbles) as an indicator for appropriate pulse energy. We hypothesize that micro bubbles, which takes place far below the appearance of macro bubbles already trigger the therapeutic benefit. Here we present two techniques and algorithms for real-time detection of the onset of micro bubbles.
The trabecular meshwork (TM) of freshly enucleated porcine eye globes was irradiated with a Nd:YLF laser at a wavelength of 527 nm. In contrast to conventional SLT, a pulse duration of 1.7 µs was used, and a series of 15 pulses with increasing energy at a repetition rate of 100 Hz per each spot of 200 µm in diameter were applied. Micro bubble formation was measured using an optoacoustic and an optical method. Detection algorithms are based on the single pulse analyses of generated optoacoustic transients and the backscattered laser light, respectively. Macro bubbles were observed ophthalmoscopically through the slit lamp.
Both observation methods are equally capable of detecting micro bubble nucleation, the thresholds vary between 26 and 124 µJ owing to the strong variations in TM pigmentation. The accuracies (following a ROC analysis) of the algorithms to distinguish whether micro bubbles are formed or not was found to be 92.9 % for the optical and 91.6 % for the optoacoustic method. In average ophthalmoscopic visible macro bubbles could be observed at energies starting around 250 µJ, thus far above micro bubble formation threshold.
We demonstrated an accurate automatic detection of micro bubble formation in SLT. In case that the therapeutically demanded pressure reduction is already achieved with these micro bubbles, which needs to be proved clinically, than the methods presented here can be used in a feedback loop controlling the laser irradiation. I.e. the pulse ramp can be automatically ceased upon detection of micro bubble formation. This will unburden the clinicians from any dosing during SLT.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
This PDF is available to Subscribers Only