Effects of laser in situ keratomileusis on tear production, clearance, and the ocular surface
Received 7 August 2000; accepted 14 February 2001.
Abstract
Purpose
To evaluate components of the integrated ocular surface/lacrimal gland unit in a series of patients before and after undergoing bilateral laser in situ keratomileusis (LASIK).
Design
Prospective, noncomparative case series.
Participants
Forty-eight eyes of 14 men and 34 women (age range, 26–54; mean, 39.2 years) who underwent bilateral LASIK for myopia or myopic astigmatism.
Methods
LASIK was performed using a VISX Star Excimer Laser (Santa Clara, CA). Patients completed a questionnaire containing 11 questions that evaluated the character and severity of ocular irritation symptoms. Snellen visual acuity, tear fluorescein clearance, corneal fluorescein staining, aqueous tear production by the Schirmer 1 test, and corneal and conjunctival sensitivity were measured in each eye. Corneal surface regularity (SRI) was evaluated with the Tomey TMS-1 (Tomey, Cambridge, MA) topography instrument. Each randomly chosen eye was evaluated 1 to 2 days (T0) before LASIK and 7 days (T1), 1 (T2), 2 (T3), 6 (T4), 12 (T5), and 16 (T6) months postoperatively. A Wilcoxon test, two-tailed paired t test, Friedman test, or analysis of variance were used for statistical comparisons.
Main outcome measures
Components of the integrated ocular surface/lacrimal gland unit.
Results
Both corneal and conjunctival sensitivity were noted to be significantly decreased from preoperative levels at 1week, 1 month, 12 months, and 16 months postoperatively (P < 0.0002 at each time point). Symptom severity scores were significantly increased at 1 week, 12 months, and 16 months postoperatively (P < 0.007 at all time points). The mean Schirmer 1 test scores were 24 ± 14 mm preoperatively, and they decreased to 18 ± 14 mm by 1 month postoperatively (P < 0.001). Tear fluorescein clearance showed a linear increase postoperatively and was significantly greater than baseline (P < 0.001) at each time point. There was a significant increase in punctate corneal fluorescein staining at 1 week postoperatively (P < 0.0001), but staining returned to baseline by 12 months. There was a statistically significant increase in SRI 1 week postoperatively (P < 0.007) with return to baseline levels by 6 months.
Conclusions
Sensory denervation of the ocular surface after bilateral LASIK disrupts ocular surface tear dynamics and causes irritation symptoms. Patients undergoing LASIK should be informed of these risks.
Manuscript no. 200474.
1Bascom Palmer Eye Institute, University of Miami School of Medicine, Miami, Florida, USA
2S. Spirito Hospital-Casale Monferrato-Alessandria-Italy and Department of Neurological and Visual Sciences, Ophthalmology, University of Genova, Genova, Italy
Reprint requests to Stephen C. Pflugfelder, MD, Cullen Eye Institute, 6565 Fannin St., NC 205, Houston, TX 77030
ABSTRACT