| southeasteyecare@hotmail.com 2006-10-14, 4:28 pm |
| Pupillary dilation from 3 to 7 mm in post-refractive surgery patients
found to cause 25- to 46-fold increase in aberrations!
BEFORE surgery, dilation from 3-7 mm caused ONLY a 5-6 fold increase in
aberrations! People complain about their bad vision when their eyes are
dilated - Imagine your vision in dim light after LASIK or PRK, with a
25-46 FOLD increase in aberrations.
http://www.ncbi.nlm.nih.gov/entrez/...st_uids=9932992
American Journal of Ophthalmology
Volume 127, Issue 1 , January 1999, Pages 1-7
Comparison of corneal wavefront aberrations after photorefractive
keratectomy and laser in situ keratomileusis.
Oshika T, Klyce SD, Applegate RA, Howland HC, El Danasoury MA.
Department of Ophthalmology, university of Tokyo School of Medicine,
Japan. oshika-tky@umin.ac.jp
PURPOSE: To compare changes in the corneal wavefront aberrations after
photorefractive keratectomy and laser in situ keratomileusis.
METHODS: In a prospective randomized study, 22 patients with bilateral
myopia received photorefractive keratectomy on one eye and laser in
situ keratomileusis on the other eye. The procedure assigned to each
eye and the sequence of surgery for each patient were randomized.
Corneal topography measurements were performed preoperatively, 2 and 6
weeks, 3, 6, and 12 months after surgery. The data were used to
calculate the wavefront aberrations of the cornea for both small (3-mm)
and large (7-mm) pupils.
RESULTS: Both photorefractive keratectomy and laser in situ
keratomileusis significantly increased the total wavefront aberrations
for 3- and 7-mm pupils, and values did not return to the preoperative
level throughout the 12-month follow-up period. For a 3-mm pupil, there
was no statistically significant difference between photorefractive
keratectomy and laser in situ keratomileusis at any postoperative
point. For a 7-mm pupil, the post-laser in situ keratomileusis eyes
exhibited significantly larger total aberrations than the
post-photorefractive keratectomy eyes, where a significant intergroup
difference was observed for spherical-like aberration, but not for
coma-like aberration. This discrepancy seemed to be attributable to the
smaller transition zone of the laser ablation in the laser in situ
keratomileusis procedure. Before surgery, simulated pupillary dilation
from 3 to 7 mm caused a five- to six-fold increase in the total
aberrations. After surgery, the same dilation resulted in a 25- to
32-fold increase in the photorefractive keratectomy group and a 28- to
46-fold increase in the laser in situ keratomileusis group. For a 3-mm
pupil, the proportion of coma-like aberration increased after both
photorefractive keratectomy and laser in situ keratomileusis. For a
7-mm pupil, coma-like aberration was dominant before surgery, but
spherical-like aberration became dominant postoperatively.
CONCLUSIONS: Both photorefractive keratectomy and laser in situ
keratomileusis increase the wavefront aberrations of the cornea and
change the relative contribution of coma- and spherical-like
aberrations. For a large pupil, laser in situ keratomileusis induces
more spherical aberrations than photorefractive keratectomy. This
finding could be attributable to the smaller transition zone of the
laser ablation in the laser in situ keratomileusis procedure.
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