title: Effect of radiation therapy on intraocular pressure in patients with Graves' orbitopathy.
abstract: OBJECTIVE
  To describe the effect of radiation therapy on intraocular pressure in patients who have had orbital radiation for Graves' orbitopathy, and to provide a descriptive analysis of these patients.
  
  
  METHODS
  Retrospective case series.
  
  
  METHODS
  24 consecutive patients referred for orbital radiation therapy for Graves' orbitopathy from December 1st, 2001 through July 31st, 2009.
  
  
  METHODS
  Patients received a total of 2000 cGy fractionated over 10 days.
  
  
  METHODS
  Medical records were reviewed for: demographics, tobacco history, ocular history, history related to Graves' disease, medications, visual field tests, retinopathy, and physical exam findings. The two-tailed Student's t-test was used to determine statistically significant differences in intraocular pressure before radiation therapy and 0-3 (T1), 4-6 (T2), 7-12 (T3), and 13-18 (T4) months following radiation therapy.
  
  
  RESULTS
  34 eyes were available for analysis. There was no correlation between intraocular pressure and SPECS scores. Mean intraocular pressure prior to radiation therapy was 18.15 ± 3.83 mm Hg. Patients who had orbital decompression, eye muscle surgery, or glaucoma were excluded from the final analysis. There were 7, 11, 14, and 11 eyes with data at times T1, T2, T3, and T4 following radiation therapy, respectively. There was a significant decrease in mean intraocular pressure at T2, T3 and T4 of 26.00% ± 9.25%, 11.75% ± 27.58%, and 16.72% ± 13.94%, respectively.
  
  
  CONCLUSIONS
  There was a significant drop in mean intraocular pressure between 4 and 18 months after radiation therapy in our patient population. The mechanism by which this decrease in intraocular pressure occurs is not understood.
authors.affiliation: Department of Ophthalmology, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA. Russell_doc@yahoo.com
authors.forename: David J
authors.initials: DJ
authors.lastname: Russell
authors.forename: Jonathan J
authors.initials: JJ
authors.lastname: Dutton
authors.forename: Rosalinda L
authors.initials: RL
authors.lastname: Baca
mesh_terms: D019583:Dose Fractionation, Radiation; D005260:Female; D049970:Graves Ophthalmopathy / Q000532:radiotherapy*; D006801:Humans; D007429:Intraocular Pressure / Q000528:radiation effects*; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D012307:Risk Factors; D016896:Treatment Outcome