title: Intraocular pressure spike after YAG iridotomy in patients with pigment dispersion.
abstract: BACKGROUND
  The role of laser peripheral iridotomy to break a suspected reverse pupil block in the long-term control of pigment dispersion is promising, but the usefulness of this procedure has not been completely established. The author examined whether patients with pigment dispersion are at higher risk for an intraocular pressure (IOP) spike after laser peripheral iridotomy due to possible compromise of trabecular meshwork function, compared with patients undergoing prophylactic peripheral iridotomy for an occludable angle.
  
  
  METHODS
  Data were collected prospectively on the first eye of 87 patients with occludable angles and 13 patients with pigment dispersion treated with peripheral laser iridotomy between November 1995 and October 1996 at the glaucoma service of a university-affiliated hospital in Toronto. All patients received one drop of 0.5% apraclonidine before the procedure. IOP was measured before and 1 and 24 hours after the procedure.
  
  
  RESULTS
  There was no difference between the two groups in the distribution of right vs. left eyes, sex, race, the mean total energy required to produce a patent iridotomy, the mean number of medications used or the mean IOP before the procedure. The patients with pigment dispersion were significantly younger than those with occludable angles (mean age [and standard deviation (SD)] 40.5 [9.45] years vs. 66.4 [10.78] years) (p < 0.001). There was no difference between the two groups in mean IOP at 1 hour or at 24 hours. Twenty-nine patients (33%) in the occludable angle group and seven (54%) in the pigment dispersion group had an IOP spike greater than 2 mm Hg after the procedure (p = 0.001). Among these patients, the mean IOP (36.4 [SD 10.83] mm Hg vs. 30.3 [SD 7.04] mm Hg, p = 0.05) and the mean rise in IOP (14.0 [SD 10.63] mm Hg vs. 8.7 [SD 4.73] mm Hg, p = 0.04) were significantly higher in those with pigment dispersion than in those with occludable angles. Among the patients who used antiglaucoma medications before the procedure or had a prelaser IOP level greater than 22 mm Hg, those with pigment dispersion were more likely than those with occludable angles to have an IOP spike at 1 hour (p < or = 0.005).
  
  
  CONCLUSIONS
  Patients with pigment dispersion undergoing iridotomy to break a reverse pupil block should be carefully assessed after the procedure, as significant pressure spikes requiring treatment may occur.
authors.affiliation: Department of Ophthalmology, Sunnybrook and Women's College Health Sciences Centre, 2075 Bayview Ave., Toronto, ON M4N 3M5. c.birt@utoronto.ca
authors.forename: Catherine M
authors.initials: CM
authors.lastname: Birt
mesh_terms: D000368:Aged; D017889:Exfoliation Syndrome / Q000503:physiopathology* / Q000601:surgery*; D005260:Female; D006801:Humans; D007429:Intraocular Pressure; D007498:Iris / Q000601:surgery*; D053685:Laser Therapy / Q000009:adverse effects*; D008297:Male; D008875:Middle Aged; D011184:Postoperative Period; D011446:Prospective Studies