Abstract
Purpose :
Our overall objective is to develop a femtosecond laser system designed to deliver pulses aimed at preventing and treating vitreoretinal disease. Here, we sought to determine the feasibility of delivering our laser to in vitro retinal surfaces, detect pulse energy-dependent changes in laser-induced burn patterns, and measure how vitreous degenerates pulse morphology.
Methods :
In Experiment 1, equatorially bisected pig eyes (n=2) were mounted in our laser system. Single-shot ultra-short laser pulses (800nm; 10mm diameter spot size; 28fs pulse duration) were delivered from a Ti:Sapphire chirped-pulse-amplification laser system. Pulse duration was measured by a Frequency-Resolved Optical Gating (FROG) system and compressed by optimizing diffraction-grating optical compressor spatial parameters. Laser-induced retinal burns were imaged using scanning-electron microscopy. Total burn area was measured using ImageJ. One-way analysis of variance (ANOVA) was used to assess effects of pulse energy on burn area. In Experiment 2, laser pulses were passed through: (1) empty glass container; (2) glass container filled with pig vitreous to 20mm depth; and (3) same condition as (2) with compensated pulse parameters. Full-width half maximum (FWHM) of the pulse temporal and spectral profiles were extracted from FROG measurements.
Results :
In Experiment 1, femtosecond laser-induced burns were observed in retinae. Total burn area (mm2±SD) was measured across four energy levels: 12nJ (2,346.7±378.8; n=4), 115nJ (4,968.1±347.1; n=2), 12mJ (15,220.4±6974.3; n=5), 21mJ (7,174.1±2388.9; n=5). One-way ANOVA revealed an effect of laser energy on total burn area (F(3,12)=7.52, p=.0043). In Experiment 2, vitreous degenerated pulse morphology. Relative to the empty glass container, 20mm of vitreous introduced a 78% increase in temporal FWHM and a 4% increase in spectral FWHM. Compensating for pulse morphology degeneration, by contrast, produced a 4% decrease in temporal FWHM and a 16% decrease in spectral FWHM relative to empty glass container.
Conclusions :
Our femtosecond laser delivers ablative pulses that scale with pulse energy. Vitreous imposes non-zero degenerative effects on laser pulse morphology that can be corrected. These results will be informative for further developing this system to deliver therapeutic laser pulses aimed at preventing and treating vitreoretinal disease.
This is a 2021 ARVO Annual Meeting abstract.