Elsevier

Ophthalmology

Volume 109, Issue 8, August 2002, Pages 1447-1452
Ophthalmology

Effect of myopic laser in situ keratomileusis on epithelial and stromal thickness: a confocal microscopy study

Presented in part at the annual meeting of the Association for Research in Vision and Ophthalmology, Fort Lauderdale, Florida, May 2001.
https://doi.org/10.1016/S0161-6420(02)01106-5Get rights and content

Abstract

Purpose

To determine changes in central epithelial and stromal thickness in human corneas in vivo after laser in situ keratomileusis (LASIK).

Design

Prospective, nonrandomized, comparative trial.

Participants

Eighteen eyes of 12 patients received LASIK (performed using the VISX Star laser [VISX, Santa Ana, CA]) with a planned 180-μm flap (created using an automated Hansatome microkeratome [Bausch & Lomb, Irvine, CA]) to correct refractive errors between −2.0 diopters (D) and −11.0 D.

Methods

Corneas were examined by using confocal microscopy in vivo before LASIK and at 1 week and 1, 3, 6, and 12 months after LASIK. Epithelial thickness was the distance between images of the surface epithelium and subbasal nerve plexus or, when nerves were not visible, the subbasal peak (if present in the light intensity profile). Total flap thickness was the distance between images of the surface epithelium and interface debris (or peak), and total stromal thickness was the distance between images of the most anterior keratocytes and endothelium.

Main outcome measures

Corneal epithelial and stromal thickness.

Results

Epithelial thickness before LASIK was 46 ± 5 μm (mean ± standard deviation) and increased 22% by 1 month after LASIK (56 ± 5 μm; P = 0.01). Thereafter, epithelial thickness did not change, but remained thicker at 12 months after LASIK (54 ± 8 μm) than before LASIK (P = 0.02). Total flap thickness at 1 month after LASIK was 160 ±28 μm and did not change thereafter. Changes in total stromal thickness between 1 and 12 months after LASIK were not significant.

Conclusions

The central corneal epithelium was thicker in the first year after LASIK than before LASIK. There was no change in central stromal thickness between 1 month and 12 months after LASIK.

Section snippets

Subjects

Twenty-seven eyes of 14 patients were enrolled prospectively in a nonrandomized fashion from August 1998 through January 1999. All participants were patients of the Mayo Clinic, Rochester, Minnesota. Exclusion criteria included wearing contact lenses within 2 weeks (soft lenses) or 3 weeks (rigid lenses) of the study, diabetes mellitus or other significant chronic disorders, glaucoma or ocular hypertension (≥22 mmHg), use of any ocular medications, and use of any systemic medications known to

Results

No epithelial defects or flap abnormalities occurred during or after the LASIK procedure. All corneas healed without clinical evidence of haze, interface abnormalities, or inflammation.

Discussion

We have used confocal microscopy in vivo to study changes in the thickness of the central cornea and its layers after myopic LASIK. Our longitudinal study showed that epithelial thickness increased 22% by 1 month after LASIK compared with before LASIK, presumably because of epithelial hyperplasia. Thereafter, epithelial thickness did not change, but remained thicker than before LASIK. Our confocal microscopy study confirms previous high-frequency ultrasound studies,6, 7, 8 which also showed

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Supported by the National Institutes of Health, Bethesda, Maryland (grant no.: EY02037); Research to Prevent Blindness, Inc., New York, New York; and the Mayo Foundation, Rochester, Minnesota.

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