Scanning laser polarimetry of retinal nerve fibre layer thickness after laser assisted in situ keratomileusis (LASIK): stability of the values after the third post-LASIK month.
BACKGROUND
Monitoring the retinal nerve fibre layer thickness (RNFLT) is essential in the diagnosis and treatment of glaucoma. In a previous study we found that a decrease of the polarimetric RNFLT observed in the early period after laser-assisted in situ keratomileusis (LASIK) disappears or tends to disappear by the third post-LASIK month.


OBJECTIVE
To study the stability of the "recovered" polarimetric retardation values between the third and twelfth month after LASIK.


METHODS
Scanning laser polarimetry (SLP) with the classic GDx Nerve Fiber Analyzer was performed on 13 consecutive healthy subjects with no eye disease who underwent LASIK for ametropia correction. Measurements were performed preoperatively, then at 3 and 12 months postoperatively.


RESULTS
Inferior, temporal and nasal average thickness as well as ellipse average thickness and average thickness showed no difference among the three time points (ANOVA, p > 0.05). Superior average thickness was significantly smaller both at three months (Sheffe test, p =0.008) and 12 months (p =0.006) than before LASIK. However, no difference was seen between the values measured at three months and at 12 months after LASIK (p =0.997). A statistically significant interaction between treatment type (myopic or hyperopic correction) and the change of retardation was found for the superior average thickness (two-way ANOVA, p =0.016). In this quadrant the RNFLT values of the myopic eyes decreased between the baseline and the month 3 measurements but became stable after that; the retardation of the hyperopic eyes remained unchanged throughout.


CONCLUSIONS
RNFLT measured with the classic GDx device after LASIK shows transient changes probably due to the LASIK-induced alteration of the polarization and the healing process. The polarimetric RNFLT values, however, become stable by the third post-LASIK month, and show no further change until the end of the first year after LASIK. Baseline SLP measurements for long-term glaucoma follow-up can be obtained from the third post-LASIK month onwards.
1st Department of Ophthalmology, Semmelweis University, Budapest, Hungary.
A
A
Katsanos
P
P
Kóthy
Z Z
ZZ
Nagy
G
G
Holló
D000328:Adult; D000704:Analysis of Variance; D003319:Corneal Stroma / Q000601:surgery*; D003941:Diagnostic Techniques, Ophthalmological; D005500:Follow-Up Studies; D005901:Glaucoma / Q000175:diagnosis* / Q000209:etiology; D006801:Humans; D007429:Intraocular Pressure; D020731:Keratomileusis, Laser In Situ / Q000009:adverse effects*; D008859:Microscopy, Polarization; D008875:Middle Aged; D009412:Nerve Fibers; D009887:Ophthalmoscopy; D011184:Postoperative Period; D012016:Reference Values; D054140:Refractive Surgical Procedures; D015203:Reproducibility of Results; D012160:Retina / Q000473:pathology; D012165:Retinal Ganglion Cells / Q000473:pathology*; D014065:Tonometry, Ocular