title: Effects of laser in situ keratomileusis on tear production, clearance, and the ocular surface.
abstract: OBJECTIVE
  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).
  
  
  METHODS
  Prospective, noncomparative case series.
  
  
  METHODS
  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.
  
  
  METHODS
  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.
authors: Bascom Palmer Eye Institute, University of Miami School of Medicine, Miami, Florida, USA.
authors: L
authors: L
authors: Battat
authors: A
authors: A
authors: Macri
authors: D
authors: D
authors: Dursun
authors: S C
authors: SC
authors: Pflugfelder
mesh_terms: D000328:Adult; D001251:Astigmatism / Q000601:surgery; D003229:Conjunctival Diseases / Q000175:diagnosis / Q000209:etiology* / Q000378:metabolism; D003315:Cornea / Q000294:innervation / Q000473:pathology; D003316:Corneal Diseases / Q000175:diagnosis / Q000209:etiology* / Q000378:metabolism; D003714:Denervation; D015352:Dry Eye Syndromes / Q000209:etiology* / Q000378:metabolism; D005260:Female; D019793:Fluorescein / Q000378:metabolism / Q000493:pharmacokinetics; D015590:Fluorophotometry; D006801:Humans; D006987:Hypesthesia / Q000175:diagnosis / Q000209:etiology* / Q000378:metabolism; D020731:Keratomileusis, Laser In Situ / Q000009:adverse effects*; D008297:Male; D008875:Middle Aged; D009216:Myopia / Q000601:surgery; D009882:Ophthalmic Nerve / Q000601:surgery; D011446:Prospective Studies; D011795:Surveys and Questionnaires; D013666:Tears / Q000378:metabolism*; D014110:Touch; D014792:Visual Acuity
chemical_list: D019793:Fluorescein