Original article
Retinal nerve fiber layer thickness remains unchanged following laser-assisted in situ keratomileusis1,

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Abstract

PURPOSE: To evaluate the effect of laser-assisted in situ keratomileusis (LASIK) on retinal nerve fiber layer (RNFL) thickness measurements obtained with scanning laser polarimetry (SLP), optical coherence tomography (OCT), and scanning laser tomography (SLT).

DESIGN: Interventional case series.

METHODS: Twenty eyes (20 patients) undergoing LASIK were enrolled in this prospective study. SLP, OCT, and SLT examinations were performed 1 week prior to and 1 week and 4 weeks after LASIK surgery. Intraocular pressure was normal at all preoperative and postoperative examinations. SLP, OCT, and SLT mean RNFL thickness values, and SLT RNFL cross sectional area, rim area, and rim volume before and after LASIK were compared by the Student paired t test.

RESULTS: Mean patient age was 39.3 ± 9.5 (SD) years (range, 28 to 62 years). Mean preoperative spherical equivalent refractive error was −3.9 ± 1.9 diopters (D) (range, −1.4 to −8.00 D) and mean spherical equivalent refractive surgical correction was 3.6 ± 1.9 D (range, 1.00 to 8.50 D). Mean RNFL thicknesses obtained by SLP were thinner 1 week and 4 weeks after LASIK (P < 0.01, for all comparisons, paired t test), whereas mean OCT RNFL thickness and SLT RNFL thickness, RNFL cross-section area, rim area, and rim volume measurements were unchanged 1 week and 4 weeks after LASIK (P ≥ 0.05, for all comparisons, paired t test).

CONCLUSIONS: LASIK does not affect RNFL thickness. Alterations in SLP RNFL thickness measurements are due to alterations in corneal architecture rather than an actual LASIK-induced RNFL injury.

Section snippets

Methods

Patients undergoing LASIK by two of the authors (D.F.B., B.D.S.) were enrolled in this prospective study. One eye was chosen randomly if both eyes were scheduled for surgery. Informed consent was obtained from each subject using a consent form approved by the Institutional Review Board for Human Research of the New York Eye and Ear Infirmary.

Inclusion criteria included absence of ophthalmic disease other than myopia and astigmatism, and no family history of glaucoma. Exclusion criteria included

Results

Twenty eyes of 20 patients were enrolled (7 males, 13 females). Mean patient age was 39.3 ± 9.5 (SD) years (range, 28 to 62 years). Mean preoperative and postoperative spherical equivalent refractive errors were −3.9 ± 1.9 diopters (D) (range, −1.4 to −8.00 D) and −0.3 ± 0.4 D (range, −1.4 to 0.5 D), respectively. Mean spherical equivalent refractive surgical correction was 3.6 ± 1.9 D (range, 1.00 to 8.50 D).

Total mean RNFL and superior, inferior, temporal, and nasal mean RNFL thicknesses

Discussion

Computerized imaging devices offer the potential for reliable, reproducible, objective measurement of structural injury in glaucoma. OCT and SLP provide an assessment of RNFL structure by utilizing different optical techniques. OCT evaluates reflectance of posterior segment structures and incorporates a mathematical algorithm capable of localizing the anterior and posterior limits of the RNFL.8, 11 This provides a direct measurement of RNFL thickness. SLP utilizes the birefringence

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This work was supported in part by the New York Glaucoma Research Institute, New York, NY.

1

The authors have no financial interest in any device or technique described in this paper.

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