Ablation smoothness as a function of excimer laser delivery system.
OBJECTIVE
To quantitatively study and compare the ablation profiles of three kinds of excimer laser delivery systems to identify which technology provides the smoothest ablation profile.


METHODS
Three private practices, one in Canada and two in the United States.


METHODS
Excimer laser myopic ablations were performed on poly(methyl methacrylate) (PMMA) test blanks in 3.00 diopter increments using a 5 mm optical zone with three kinds of excimer laser delivery systems: (1) iris diaphragm without beam-homogenizing technology (ExciMed, Summit Technologies, Inc.); (2) iris diaphragm with beam homogenizer (20/20, VISX, Inc.); (3) galvanometric scanning (Mini-Excimer, LaserSight, Inc.). We used a scanning white-light interferometer (NewView 100, Zygo Corp.) to study three measures of surface smoothness: peak to valley, root mean square average deviation height (RMS), and the arithmetic average deviation from the center line of the data.


RESULTS
Using RMS as a measure of surface smoothness in an optical system, the galvanometric scanning delivery system produced ablations approximately three times smoother than the iris diaphragm with beam homogenizer (P = .01), which in turn produced ablations about twice as smooth as the iris diaphragm without beam homogenizer (P = .03).


CONCLUSIONS
Galvanometric scanning delivery systems provide a significantly smoother ablation profile than iris-diaphragm (variable aperture) systems.
O'Donnell
C B
CB
Kemner
J
J
O'Donnell
F E
FE
D007368:Interferometry; D054018:Lasers, Excimer; D007910:Lenses, Intraocular; D008027:Light; D020366:Methylmethacrylate; D008768:Methylmethacrylates; D018903:Photorefractive Keratectomy / Q000295:instrumentation / Q000379:methods*
D008768:Methylmethacrylates; D020366:Methylmethacrylate