title: Effect of laser in situ keratomileusis on tear stability.
abstract: OBJECTIVE
  Patients frequently experience dry eye symptoms after laser in situ keratomileusis (LASIK). The mechanisms that lead to these changes are not well understood. The purpose of this study was to investigate the effect of LASIK on tear function.
  
  
  METHODS
  Prospective, comparative, nonrandomized interventional trial.
  
  
  METHODS
  Fifty-eight consecutive patients (96 eyes) who underwent myopic LASIK treatment.
  
  
  METHODS
  The prospective study involved 58 consecutive patients (96 eyes) who underwent sequential or bilateral LASIK for the correction of myopia. Dry eye symptoms, standardized Schirmer test values, basal tear secretion test, and tear break-up time were measured before surgery and 1 day, 1 week, and 1 month after surgery.
  
  
  METHODS
  Schirmer test value, basal tear secretion value, and tear break-up time.
  
  
  RESULTS
  Before surgery, 15.6% of patients (15/96) had dry eye symptoms. After surgery, 94.8% of patients (91/96), 85.4% of patients (82/96), and 59.4% of patients (57/96) experienced dry eye symptoms at 1 day, 1 week, and 1 month, respectively. Schirmer test value (13.32 +/- 10. 67 mm) increased at 1 day (14.48 +/- 10.57 mm; P = 0.25) and subsequently decreased at 1 week (11.18 +/- 9.81 mm; P = 0.05) and at 1 month (10.83 +/- 10.02 mm; P = 0.03). Basal tear secretion test value (8.49 +/- 8.48 mm) decreased at 1 day (6.80 +/- 6.48 mm; P = 0.05), at 1 week (5.97 +/- 6.88 mm; P = 0.005), and at 1 month (5.89 +/- 6.24 mm; P = 0.007). Tear break-up time (5.32 +/- 2.35 seconds) decreased 1 day (4.14 +/- 1.90 seconds; P < 0.001) and 1 week (4.49 +/- 1.70 seconds; P = 0.004) after surgery and recovered by 1 month after surgery (5.09 +/- 3.03 seconds; P = 0.52). Poor preoperative tear functions with a Schirmer test value less than 10 mm was a significant risk factor (72% vs. 46%; relative risk, 1.58 [1.10-2.26]) for experiencing dry eye symptoms at 1 month after surgery.
  
  
  CONCLUSIONS
  Dry eye symptoms are common after myopic LASIK surgery. Laser in situ keratomileusis significantly altered the tear break-up time, Schirmer test values, and basal tear secretion. Patients with preexisting tear flow abnormality as demonstrated by Schirmer test values less than 10 mm are especially at risk of experiencing dry eye symptoms.
authors.affiliation: Department of Ophthalmology and Visual Sciences, Chinese University of Hong Kong, Kowloon, Hong Kong.
authors.forename: E Y
authors.initials: EY
authors.lastname: Yu
authors.forename: A
authors.initials: A
authors.lastname: Leung
authors.forename: S
authors.initials: S
authors.lastname: Rao
authors.forename: D S
authors.initials: DS
authors.lastname: Lam
mesh_terms: D000328:Adult; D001251:Astigmatism / Q000601:surgery; D003315:Cornea / Q000601:surgery; D015352:Dry Eye Syndromes / Q000209:etiology* / Q000378:metabolism; D005260:Female; D006801:Humans; D020731:Keratomileusis, Laser In Situ / Q000009:adverse effects*; D007765:Lacrimal Apparatus / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D009216:Myopia / Q000601:surgery; D011446:Prospective Studies; D013666:Tears / Q000378:metabolism*