title: Baseline characteristics of participants in the natural history study of macular telangiectasia (MacTel) MacTel Project Report No. 2.
abstract: OBJECTIVE
  To describe the baseline characteristics of a large international cohort of patients with macular telangiectasia type 2 (MacTel Type 2) in anticipation of a longitudinal natural history study to evaluate structural and functional changes, identify potential risk factors and related outcomes.
  
  
  METHODS
  Images including fundus photographs, fluorescein angiograms, optical coherence tomography and fundus autofluorescence were collected. A grading system for MacTel type 2 was developed by the central reading center to evaluate lesion characteristics. Relationships between lesion characteristics and visual acuity were evaluated.
  
  
  RESULTS
  A total of 310 participants have been enrolled in the study. The mean time since diagnosis was 3 years (range 0 to 25 years). The mean age at the baseline examination was 61 +/- 9 years. The mean visual acuity in the better eye was approximately 20/32 Snellen equivalents and approximately 20/50 in the worse eye. The visual acuity in the better eye of half of the participants was 20/32 or better. We found some relationships between visual acuity and lesions characteristic of MacTel Type 2.
  
  
  CONCLUSIONS
  This is the first large-scale study of patients with MacTel Type 2. More than half of the patients had 20/32 or better vision in their better eye, which is a sign that decreased function in these participants may not be reflected in central visual acuity. These findings highlight the limitation of using visual acuity measurements as a measure of function and as an outcome measure in potential clinical trials in patients with MacTel Type 2.
authors.affiliation: The EMMES Corporation, Rockville, MD 20850, USA. tclemons@emmes.com
authors.forename: Traci E
authors.initials: TE
authors.lastname: Clemons
authors.forename: Marc C
authors.initials: MC
authors.lastname: Gillies
authors.forename: Emily Y
authors.initials: EY
authors.lastname: Chew
authors.forename: Alan C
authors.initials: AC
authors.lastname: Bird
authors.forename: Tunde
authors.initials: T
authors.lastname: Peto
authors.forename: Maria J
authors.initials: MJ
authors.lastname: Figueroa
authors.forename: Molly W
authors.initials: MW
authors.lastname: Harrington
mesh_terms: D000368:Aged; D005260:Female; D005451:Fluorescein Angiography; D006304:Health Status; D006801:Humans; D008297:Male; D008875:Middle Aged; D010781:Photography; D012164:Retinal Diseases / Q000145:classification / Q000175:diagnosis*; D012171:Retinal Vessels / Q000473:pathology*; D012307:Risk Factors; D013684:Telangiectasis / Q000145:classification / Q000175:diagnosis*; D013997:Time Factors; D041623:Tomography, Optical Coherence; D014792:Visual Acuity / Q000502:physiology