title: Visual symptoms and retinal straylight after laser peripheral iridotomy: the Zhongshan Angle-Closure Prevention Trial.
abstract: OBJECTIVE
  To assess the impact of laser peripheral iridotomy (LPI) on forward-scatter of light and subjective visual symptoms and to identify LPI parameters influencing these phenomena.
  
  
  METHODS
  Cohort study derived from a randomized trial, using an external control group.
  
  
  METHODS
  Chinese subjects initially aged 50 or older and 70 years or younger with bilateral narrow angles undergoing LPI in 1 eye selected at random, and age- and gender-matched controls.
  
  
  METHODS
  Eighteen months after laser, LPI-treated subjects underwent digital iris photography and photogrammetry to characterize the size and location of the LPI, Lens Opacity Classification System III cataract grading, and measurement of retinal straylight (C-Quant; OCULUS, Wetzlar, Germany) in the treated and untreated eyes and completed a visual symptoms questionnaire. Controls answered the questionnaire and underwent straylight measurement and (in a random one-sixth sample) cataract grading.
  
  
  METHODS
  Retinal straylight levels and subjective visual symptoms.
  
  
  RESULTS
  Among 230 LPI-treated subjects (121 [58.8%] with LPI totally covered by the lid, 43 [19.8%] with LPI partly covered by the lid, 53 [24.4%] with LPI uncovered by the lid), 217 (94.3%) completed all testing, as did 250 (93.3%) of 268 controls. Age, gender, and prevalence of visual symptoms did not differ between treated subjects and controls, although nuclear (P<0.01) and cortical (P = 0.03) cataract were less common among controls. Neither presenting visual acuity nor straylight score differed between the treated and untreated eyes among all treated persons, nor among those (n = 96) with LPI partially or totally uncovered. Prevalence of subjective glare did not differ significantly between participants with totally covered LPI (6.61%; 95% confidence interval [CI], 3.39%-12.5%), partially covered LPI (11.6%; 95% CI, 5.07%-24.5%), or totally uncovered LPI (9.43%; 95% CI, 4.10%-10.3%). In regression models, only worse cortical cataract grade (P = 0.01) was associated significantly with straylight score, and no predictors were associated with subjective glare. None of the LPI size or location parameters were associated with straylight or subjective symptoms.
  
  
  CONCLUSIONS
  These results suggests that LPI is safe regarding measures of straylight and visual symptoms. This randomized design provides strong evidence that treatment programs for narrow angles would be unlikely to result in important medium-term visual disability.
authors.affiliation: State Key Laboratory, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China.
authors.forename: Nathan
authors.initials: N
authors.lastname: Congdon
authors.forename: Xixi
authors.initials: X
authors.lastname: Yan
authors.forename: David S
authors.initials: DS
authors.lastname: Friedman
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Foster
authors.forename: Thomas J T P
authors.initials: TJ
authors.lastname: van den Berg
authors.forename: Michelle
authors.initials: M
authors.lastname: Peng
authors.forename: Rita
authors.initials: R
authors.lastname: Gangwani
authors.forename: Mingguang
authors.initials: M
authors.lastname: He
mesh_terms: D000368:Aged; D015331:Cohort Studies; D005260:Female; D019466:Glare; D015812:Glaucoma, Angle-Closure / Q000517:prevention & control*; D006801:Humans; D007429:Intraocular Pressure; D032801:Iridectomy; D007498:Iris / Q000601:surgery; D053685:Laser Therapy; D053844:Lasers, Solid-State; D008027:Light; D008297:Male; D008875:Middle Aged; D011183:Postoperative Complications; D012160:Retina / Q000528:radiation effects*; D012164:Retinal Diseases / Q000209:etiology*; D012307:Risk Factors; D012542:Scattering, Radiation; D011795:Surveys and Questionnaires; D014786:Vision Disorders / Q000209:etiology*; D014792:Visual Acuity / Q000502:physiology