Abstract
Abstract: :
Purpose: To determine if there is a measurable difference in intra–ocular pressure after myopic LASIK compared to myopic PRK. Methods: A retrospective analysis was performed on patients undergoing elective LASIK or PRK. This study includes 46 eyes from 24 patients, 16 myopic PRK eyes, 22 myopic LASIK eyes {Please note more patients will be added to each group prior to final publication of abstract book.) IOP measurements were performed by applanation tonometry and pneumotonometry before and after surgery, ablation depth was ascertained at the time of surgery. A paired t–test was used to evaluate IOP measurements for each group of patients with each instrument. Results: The average correction for PRK eyes in this study was –5.04 D with a range of –2.43 to –7.51, the average ablation depth was 77.8 microns. The difference between pre and post op pressures was significant by applanation –3.1 (p=.00278) but not by pneumotononometry (p=.225985). The average correction for the myopic LASIK eyes was (–4.80 D (–1.46 to –7.76), the average ablation depth was 70.98 microns. The difference between pre operative and post operative IOP values was significant for applanation tonometry, –3.1 (p=.00000261497) but not for pneumotonometry (p=.059748). There was no significant difference in the change in IOP measurement as measured by applanation between the PRK and LASIK groups (p=.932846). Conclusion: In this group of patients both LASIK and PRK were found to cause a similar and significant difference in IOP calculations by applanation tonometry. This is consistent with previous reports indicating a decrease in IOP measurements after PRK or LASIK due to a decrease in corneal thickness. It appears that the absence of a central Bowman's membrane, seen in PRK, but not LASIK, does not affect the amount of pressure reduction after corneal laser refractive surgery, when measuring intraocular pressure by applanation following refractive surgery.
Keywords: refractive surgery: comparative studies • intraocular pressure • myopia