Free radical production by Nd:YAG laser photodisruption.
OBJECTIVE
Plasma and cavitation bubble formation during optical breakdown in aqueous media may produce hydroxyl (*OH) radicals. The authors' objectives were to detect *OH produced by a neodymium:yttrium-aluminum-garnet (Nd:YAG) laser photodisruptor and to determine *OH concentration in relation to laser energy.


METHODS
*OH was assayed by measuring absorbance of triiodide (I3-) in a potassium iodide (KI) solution exposed to optical breakdown by an Nd:YAG laser. The concentration-dependent reduction of radical production in relation to cystamine concentration was evaluated.


RESULTS
I3- concentration increased linearly with total irradiation energy and decreased exponentially with increasing cystamine concentration. *OH concentration was calculated using extinction coefficients of I3- and chemical equations relating I3- formation to *OH.


CONCLUSIONS
The authors calculated that approximately 4 x 10(-12) moles of *OH are produced in a typical posterior capsulotomy of 100 mJ of total energy. This *OH concentration could produce strand breaks in approximately 0.4% of vitreous hyaluronic acid molecules, but is unlikely to produce clinical effects.
Timberlake
G T
GT
Department of Ophthalmology, University of Kansas Medical Center, Kansas City 66160-7379, USA.
Gemperli
A W
AW
Larive
C K
CK
Warren
K A
KA
Mainster
M A
MA
D001082:Aqueous Humor / Q000378:metabolism* / Q000528:radiation effects*; D003538:Cystamine / Q000378:metabolism / Q000528:radiation effects; D005609:Free Radicals / Q000378:metabolism / Q000528:radiation effects; D006801:Humans; D007834:Lasers; D013053:Spectrophotometry
D005609:Free Radicals; D003538:Cystamine