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M. Parsons; Characteristics of Pre-Op PRK Patients and the Role of Corneal Wound Healing in Observed Emmetropic Trends. Invest. Ophthalmol. Vis. Sci. 2009;50(13):910.
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The purpose of this study is to perform a retrospective database analysis on the refractive status and visual performance of USAF aircrew from months 1 to 12 after PRK
727 eyes were examined retrospectively at sites across the Department of Defenese for post-op results after undergoing myopic PRK. Age, pre-op refraction, post-op refraction, surgical site, surgical date, and haze data were evaluated. Eyes were analyzed at 1,2,3,4,6, and 12 month intervals.
Eyes were assigned to groups 1-3 as below based on cycloplegic and manifest refraction. Group 1 was considered emmetropic at 1 month post-op, and Group 2-3 were >1.0 and <0.75 at 1 month respectively. Both Group 2 and Group 3 eyes had statistically significant trends toward emmetropia from post-op month 1 to 12 based on cycloplegic and manifest refractions.Cycloplegic Rx738 eyes followed603 were (-0.5-0.5 D) = Group 158 were >1.0 D = Group 277 were <0.75 D= Group 3Manifest Rx727 eyes followed593 were (-0.5-0.5) =Group 157 were >1.0 =Group 277 were <-0.75 =Group 3Time of year and age had no statistically significant impact on post-op month 1 result.
Both Group 2 and Group 3 eyes trended towards emmetropia in our retrospective data. It is well known in the literature that overcorrected eyes tend to undergo myopic regression as we saw in Group 2 eyes. Myopic regression is believed to be determined in part by the amount of stromal re-thickening which occurs in the photoablation center. One of the current thoughts is that the depth of the photoablation may be the principal factor determining the degree of myopic regression due to a larger wound inciting a larger inflammatory reaction. Our data however, does not support this finding.As mentioned above, our data also shows a statistically significant trend toward emmetropia in Group 3 (<0.75 D) eyes. It is currently unclear what may be causing this hyperopic shift. One possible explanation for this finding could be that there is indeed is cell regrowth, however perhaps it is being counteracted by some other force, such as prolonged apoptosis leading to stromal rethinning. Trying to explain this hyperopic shift and this emmetropic trend in Group 3 eyes will be the subject of future projects
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