Corneal barrier function, tear film stability, and corneal sensation after photorefractive keratectomy and laser in situ keratomileusis

https://doi.org/10.1016/j.ajo.2004.08.039Get rights and content

Purpose

To compare corneal sensation, corneal barrier function, tear secretion, and tear film stability after photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK).

Design

Prospective, nonrandomized clinical trial.

Methods

In a prospective study, 28 eyes of 15 patients underwent PRK and 115 eyes of 59 patients underwent LASIK to correct myopia. Corneal sensation, corneal epithelial barrier function, tear secretion, and tear film stability were examined preoperatively and 1 week and 1, 3, 6, and 12 months postsurgery.

Results

Both PRK and LASIK significantly compromised corneal sensation, increased epithelial barrier function, reduced tear secretion, and deteriorated tear film stability (P < .05, Wilcoxon signed-rank test). Deterioration of corneal sensation was significantly greater after LASIK than after PRK by 3 months postoperatively (P < .05, Wilcoxon rank sum test). Increases in corneal epithelial permeability were more prolonged after LASIK than after PRK. A significant intergroup difference in permeability was observed 1 month after surgery (P < .01). Tear breakup time was significantly shorter in the LASIK group than in the PRK group up to 3 months after surgery (P < .045).

Conclusions

LASIK induces greater and more prolonged damage to corneal sensation, corneal barrier function, and tear film stability than PRK.

Section snippets

Patients and methods

We recruited 74 consecutive patients who were undergoing refractive surgery for correction of myopia between July and December 2001. Patients having systemic or ocular diseases such as diabetes mellitus, connective tissue disease, ocular surface disease, corneal disease including anterior basement membrane dystrophy, cataract, glaucoma, and retinal disease were excluded from this study. The research followed the tenets of the Declaration of Helsinki, and informed consent was obtained from all

Results

The number of eyes assessed at each examination point is shown in Table 1. More than 90% of patients were followed up for 1 year. Preoperatively, there was no difference between the PRK and LASIK groups in corneal sensation (Table 2), corneal epithelial permeability (Table 3), tear secretion (Table 4), and tear breakup time (Table 5). The preoperative pachymetry was 537.7 ± 33.8 μm in the PRK group and 542.9 ± 29.0 μm in the LASIK group (P = .843, Wilcoxon rank sum test). The mean laser

Discussion

In PRK, removal of the corneal epithelium and anterior stroma causes damage to the nerve plexus in the superficial cornea. Conversely, injury of the corneal sensory nerve in LASIK occurs at the deeper corneal stroma during the process of creating the lamellar flap. Corneal sensory nerves penetrate the limbus, form thick nerve bundles in the anterior third stroma, then bend 90 degrees, penetrate Bowman’s layer, and form the basal epithelial–subepithelial nerve plexus between the basal epithelial

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