Scanning laser polarimetry (SLP) estimates retinal nerve fiber layer (RNFL) th ickness through measurement of retardation of polarized light passing through th e birefringent RNFL and cornea. A compensation method is incorporated to elimina te the anterior segment contribution to the total birefringence measured. LASIK is a technique that corrects myopia by ablating corneal tissue. This study evalu ated RNFL measurements before and after LASIK as determined by SLP with a new cu stom compensation device set for the individual cornea before and after ablation . Interventional case series. Patients underwent SLP measurements before and 30 days after LASIK for high myopia with customized compensation for anterior segme nt birefringence. Postoperative measurements were obtained with both the same co mpensation as was used preoperatively and with newly determined customized compe nsation. Standard RNFL parameters obtained before and after ablation with custom ized compensation were compared by use of paired Student’s t tests with Bonferr oni’s correction for multiple comparisons. Postoperative measurements were also compared with those obtained preoperatively with the same corneal compensation measures as used preoperatively. Retinal nerve fiber layer parameters as determi ned by SLP before and after LASIK with 2 custom cornea compensator settings post operatively. Fifty-seven eyes of 29 patients with myopia >-5.00 diopters under went LASIK (average central ablation depth 101±11.3 μm). None of the 13 parame ters showed statistically significant differences between preoperative and posto perative values with individually determined corneal compensation. When the preo perative corneal compensation was used postoperatively, 10 of 13 parameters were significantly changed. Comparison of the compensator settings before and after LASIK showed substantial differences in some individuals. On the average, there was a statistically significant change in the slow polarization axis of the corn ea, with no statistically significant change in the magnitude of the birefringen ce, with some eyes showing increases and others decreases. The change in an indi vidual cornea could not be predicted. Changes in RNFL measurements by SLP observ ed after LASIK in patients with high myopia are due to changes in corneal birefringence. These R NFL changes are not seen when customized compensation is applied for the cornea. Thus, LASIK does change the corneal birefringence but does not affect the RNFL.
展开▼
