title: Supplemental oxygen improves diabetic macular edema: a pilot study.
abstract: OBJECTIVE
  Diabetic macular edema (DME) is the most common cause of moderate visual disability in persons of working age in the United States. The pathogenesis of DME is poorly understood. In this study, the effect of retinal hypoxia in the development and maintenance of DME was investigated.
  
  
  METHODS
  Five patients with chronic DME despite at least one focal laser photocoagulation treatment (nine eyes) received 4 L/min of inspired oxygen by nasal cannula for 3 months. Best corrected visual acuity (VA) and retinal thickness, assessed by optical coherence tomography (OCT), were measured at baseline, during 3 months of oxygen treatment, and for 3 months after stopping oxygen.
  
  
  RESULTS
  After 3 months of oxygen therapy, nine of nine eyes with DME at baseline showed a reduction in thickness of the center of the macula. Foveal thickness (FTH) above the normal range was reduced by an average of 43.5% (range, 14%-100%), excess foveolar thickness (CEN) was reduced by an average of 42.1% (range, 13%-100%), and excess macular volume was reduced by an average of 54% (range, 35%-100%). Statistical analyses suggested that these changes were unlikely to be due to chance (P = 0.0077 by Wilcoxon signed-rank test). Three eyes showed improvement in VA by at least 2 lines, one by slightly less than 2 lines, and five eyes showed no change. Three months after discontinuation of oxygen, five of the nine eyes showed increased thickening of the macula compared with when oxygen was discontinued.
  
  
  CONCLUSIONS
  Supplemental inspired oxygen may decrease macular thickness due to DME, suggesting that retinal hypoxia is involved in the development and maintenance of DME.
authors.affiliation: Department of Ophthalmology, Johns Hopkins University School of Medicine, Baltimore, Maryland 21287-9277, USA.
authors.forename: Quan Dong
authors.initials: QD
authors.lastname: Nguyen
authors.forename: Syed Mahmood
authors.initials: SM
authors.lastname: Shah
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Van Anden
authors.forename: Jennifer U
authors.initials: JU
authors.lastname: Sung
authors.forename: Susan
authors.initials: S
authors.lastname: Vitale
authors.forename: Peter A
authors.initials: PA
authors.lastname: Campochiaro
mesh_terms: D000368:Aged; D002908:Chronic Disease; D003924:Diabetes Mellitus, Type 2 / Q000150:complications; D003930:Diabetic Retinopathy / Q000209:etiology / Q000473:pathology / Q000628:therapy*; D005260:Female; D006442:Glycated Hemoglobin / Q000032:analysis; D006801:Humans; D000860:Hypoxia / Q000150:complications / Q000628:therapy; D008269:Macular Edema / Q000209:etiology / Q000473:pathology / Q000628:therapy*; D008297:Male; D008875:Middle Aged; D010102:Oxygen Inhalation Therapy; D010865:Pilot Projects; D012160:Retina / Q000473:pathology; D041623:Tomography, Optical Coherence; D014792:Visual Acuity / Q000502:physiology
chemical_list: D006442:Glycated Hemoglobin