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Home > Archive > Lasik Eyes Surgery > October 2004 > PRK Stable after 12 Years
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PRK Stable after 12 Years
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| Glenn - USAEyes.org 2004-10-05, 7:10 pm |
| Comment:
Considering the techniques and technologies of 12 years ago, I am
honestly surprised the percentage of dissatisfied patients is not
significantly higher.
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AAO News Release - PRK Study Finds Vision Stable after 12 Years
For Immediate Release
October 5, 2004
Contact:
Media Relations
(415) 561-8534
media@aao.org
PRK Study Finds Vision Stable after 12 Years
SAN FRANCISCO – Refractive outcomes of photorefractive keratectomy
(PRK) for correction of mild to moderate nearsightedness remain stable
from one to 12 years after the procedure. This is the conclusion of a
British study appearing in the October 2004 issue of Ophthalmology ,
the clinical journal of the American Academy of Ophthalmology. This is
the first study to follow up with refractive surgery patients for more
than 10 years after the procedure.
In this study, 68 of the original group of 120 patients in the first
excimer laser clinical trials in the United Kingdom in 1990 underwent
clinical assessment 12 years after having the PRK procedure. Though
some refractive regression occurred in the first year after the
procedure, refractive stability was maintained when checked at six and
12 years. At 12 years, 64 eyes (94 percent) had best corrected visual
acuity better than or equal to best corrected visual acuity before the
surgery.
Academy spokesperson Roger F. Steinert, MD, said, “This study
represents a major body of work addressing an area of vital concern to
refractive surgeons and refractive surgery candidates. Attention to
the long-term results of these procedures is an obligation to our
patients and provides an opportunity to maximize the quality of the
outcomes with which our patients will live for the rest of their
lives.”
In the original trial, patients were treated with an early broad-beam
ultraviolet laser, which was used to make a four-millimeter corneal
treatment zone, called an ablation zone. Some patients developed night
vision disturbances because the ablation zone was smaller than their
pupils. Because the pupil becomes larger at night so the eye can
receive more light, the patients could see the untreated and still
myopic circular area of the cornea that lay beyond the ablation zone.
However, all reported improvement in their night vision over the
12-year period. Today, small optical zones are no longer used, and
most lasers are scanning-spot lasers, which produce a more uniform
removal of corneal tissue.
Dr. Madhavan S. Rajan, MRCOphth, FRCS, lead author of the study, said,
“This study highlights the importance of ablation zone size in
improving night vision problems and refractive predictability after
PRK. Given that PRK has proven long-term stability, newer developments
such as wavefront-guided customized ablations at the corneal surface
are likely to yield better results than LASIK, while preserving the
biomechanical integrity of the cornea.”
In the current study, 51 percent of patients were very happy with
their PRK outcomes. Ten patients (15 percent) were dissatisfied. No
corneal thinning and no late regression or complications were found.
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| ycdbsoya 2004-10-07, 7:11 pm |
| > However, all reported improvement in their night vision over the
> 12-year period.
I wonder if the reported improvement was due primarily to the
shrinking pupil as we age? Or perhaps they got used to the NVD, and
their brains eventually filtered most of it out. I remember reading
that about .6 to 1.0 mm pupil shrinkage occurs over every 10 years
after age 40. If so, it would account for a substantial portion of the
improvement but it cannot be determiined from this study.
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| ycdbsoya 2004-10-07, 7:11 pm |
| > However, all reported improvement in their night vision over the
> 12-year period.
I would think that the majority of the improvement over the study
period is due to pupil size naturally shrinking with age. I remember
reading that it ranged from 0.6 to about 1.0 mm over a ten year
period. Can't tell from the study, however. Heck, maybe they just got
used to the NVD's.
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| Ragnar Suomi 2004-10-08, 10:08 pm |
| I'd like more information about the pupil shrinking as we age.
On 7 Oct 2004 12:22:34 -0700, the_boydstons@hotmail.com (ycdbsoya)
wrote:
>
>I wonder if the reported improvement was due primarily to the
>shrinking pupil as we age? Or perhaps they got used to the NVD, and
>their brains eventually filtered most of it out. I remember reading
>that about .6 to 1.0 mm pupil shrinkage occurs over every 10 years
>after age 40. If so, it would account for a substantial portion of the
>improvement but it cannot be determiined from this study.
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