A comparative study of masking fluids for excimer laser phototherapeutic keratectomy
E. W. Kornmehl, R. F. Steinert and C. A. Puliafito
Morse Laser Center, Massachusetts Eye and Ear Infirmary, Harvard Medical School, Boston.
Several fluids of different viscosity were used to mask deeper tissues
while exposing protruding irregularities during therapeutic keratectomy of
an irregular anterior corneal surface with the 193-nm argon fluoride
excimer laser. A model of an irregular anterior corneal surface was
developed in deepithelialized calf eyes using grade 8-0 sandpaper.
Therapeutic keratectomy was then performed on 28 eyes at a fluence of 180
mJ/cm2, a repetition rate of 10 Hz, and 500 pulses per eye. Solutions of
0.3% hydroxypropylmethylcellulose 2910 and a 0.1% dextran 70 solution, 1%
carboxymethylcellulose sodium solution, or 0.9% saline solution were
applied to the corneal surface of 21 eyes. Seven control eyes underwent
ablation without the addition of fluid. Scanning electron microscopy
demonstrated that corneas treated with dextran 70 had the least surface
irregularity, and those treated with carboxymethylcellulose or saline
solution had intermediate surface irregularity. Corneas that were ablated
without additional fluid had the greatest surface irregularity. The
application of a moderately viscous solution during therapeutic excimer
laser keratectomy enhances the smoothing effect of surface ablation.
