Olivier Chatoux, David Touboul, Joseph ColinCHU Bordeaux, France

The authors have no financial interest in the subject matter of this e-poster.

Ultramicroscopy and Imaging of Crystalline Lens Photodisruption by

Femtosecond Laser

Purpose

• The aim of this study was to analyze the interactions during femtosecond Laser photodisruption into ex-vivo porcine crystalline lens.

Methods

• An experimental femtosecond laser was used

• 1030 nm wavelength,

• pulse duration 400 fs

• numerical aperture 0.13

• Specific software was created to custom and monitors any kind of photoablation patterns for treatments.

• Porcine crystalline lens were placed into an open sky holder filled with physiological liquid (BSS®) and surmounted by a glass plate.

• A numerical camera was associated with a metrological software in order to magnify and quantify the results.

• Transmission Electronic Microscopy (TEM) was performed to identify the microscopic plasma interactions with crystalline.

• More than 150 crystalline lenses of freshly enucleated pigs were treated.

• Fresh enucleated pig eye

• Crystalline lens dissection

Obtaining pig lens

magnifying glass

Control screen

Focalization lens Crystalline lens and hisHolder bathing into BSS solution

laser source

power meter Control box

Laser station

Results

• The optical breakdown threshold (OBT) was defined as the minimal energy level per pulse necessary to observe a physical interaction. In our study, with an optimized OBT of 4 µJ when the impacts were placed every 2 µm for x,y directions and 60 µm for z direction.

magnify ing numerical camera imaging

(a) above view(b) impact zone zoom(c) Minimal power used to

see impacts 4,2 µJ (right lane )

(d) longitudinal section showing filamentous impacts (arrows) capped by a cavitation bubble (¤)

Impacts spaced all the 20 µm in anterior third of the crystalline lens while varying the power of the laser on each line

a

b

c

d

magnifying numerical camera imaging

(left) longitudinal section, series of lines repeated 6 times as z axis, at constant power (3.9 μJ) for Δz ranging from 20 to 80 microns: many bubbles visible at low magnification

(right) Cross section, impacts spaced every 70 microns according to z axis: the size of an impact is 60μm on average and the impacts are not confluent, there is a space unmachined (arrows) between each impact

Ultramicroscopy imaging

• Ultramicroscopy of hexagonal crystalline lens fibers section, whithout (left) and with (right) femtosecond laser impact.

• The respect of the crystalline architecture , the non thermal effect of plasma and the innocuousness on surrounding tissues were proven by the TEM results.

Ultramicroscopy imaging

• With magnification, the center of the impact appears heterogeneous with hyperdenses and clearer zones associated with an aspect of double edging hyperdense at the edges (arrow).

coalescent bubbles disapper

• Coalescent bubbles were created by plasma formation

• For important machining (large ring), the complete coalescences bubbles disappear take about 20h (the lenses are kept in saline solution at 21 ° C)

Deformation induced by cavitation bubbles

• Some cavity were resulting from coalescence of bubbles (black arrows). The pressure exerted by the coalescences bubbles comes to deform the visible lines of impact (white arrows) and the crystalline fibers visualized in MET.

Conclusion

• The crystalline lens photodisruption by the femtosecond laser seems an innovative technique usable in the ultra precise crystalline lens cutting and to minimize the side effects. The cavitations bubbles formations kinetic and transfer have to be controlled to limit deformations of fibbers and improve the accuracy of cut.

Many thanks

Contact: olivier_chatoux@hotmail.com