title: The Novel Evidenced Assessment of Tortuosity system: interobserver reliability and agreement with clinical assessment.
abstract: OBJECTIVE
  Computer-assisted assessment of vessel tortuosity is clinically useful in retinopathy of prematurity (ROP). However, poor image quality is often prohibitive for accurate segmentation by fully automated systems and semi-automated systems are prone to unreliability. In the present work, we describe a method of retinal vessel tortuosity measurement by means of purpose-built image analysis software that does not require high image quality yet is also reliable.
  
  
  METHODS
  Images were obtained from neonates at risk of ROP with Retcam Shuttle(®) . Individual vessels were assessed with the semi-automated Novel Evidenced Assessment of Tortuosity (NEAT) system by two masked experimenters. Scores were compared to assess reliability. They were also compared against clinical scoring of individual vessels by two ROP screeners to assess relationship with clinical assessment. In a second image cohort, the mean of the most tortuous vessel in each of four quadrants in each eye (NEAT-O) was compared against the documented gold standard clinical grading of plus disease.
  
  
  RESULTS
  Reliability of the NEAT system for 50 individual vessels using Bland-Altman plots was excellent. NEAT tortuosity scores for 50 individual vessels compared to clinical scoring showed strong correlation (0.706). Correlation between the NEAT-O score for average tortuosity and gold standard for 167 eyes was modest (0.578).
  
  
  CONCLUSIONS
  The NEAT system is intuitive, user-friendly and robust enough to be clinically useful in poor-quality images. It allows for a rapid, valid and reliable assessment of tortuosity of individual vessels and produces a tortuosity score that correlates well with severity of plus disease.
authors.affiliation: Manchester Royal Eye Hospital, Central Manchester University Hospitals, NHS Foundation Trust, Manchester, UK.|Centre for Hearing and Vision Research, Medical School, University of Manchester, Manchester, UK.|Moorfields Eye Hospital, NHS Foundation Trust, London, UK.
authors.forename: Konstantinos
authors.initials: K
authors.lastname: Balaskas
authors.affiliation: Aintree University Hospitals, NHS Foundation Trust, Aintree, UK.
authors.forename: Stephanie
authors.initials: S
authors.lastname: Tiew
authors.affiliation: Departments of Eye and Vision Science and Biostatistics, Faculty of Health and Life Sciences, University of Liverpool, Liverpool, UK.
authors.forename: Gabriela
authors.initials: G
authors.lastname: Czanner
authors.affiliation: Centre for Hearing and Vision Research, Medical School, University of Manchester, Manchester, UK.
authors.forename: Ai Ling
authors.initials: AL
authors.lastname: Tan
authors.affiliation: Manchester Royal Eye Hospital, Central Manchester University Hospitals, NHS Foundation Trust, Manchester, UK.|Centre for Hearing and Vision Research, Medical School, University of Manchester, Manchester, UK.
authors.forename: Jane
authors.initials: J
authors.lastname: Ashworth
authors.affiliation: Manchester Royal Eye Hospital, Central Manchester University Hospitals, NHS Foundation Trust, Manchester, UK.|Centre for Hearing and Vision Research, Medical School, University of Manchester, Manchester, UK.
authors.forename: Susmito
authors.initials: S
authors.lastname: Biswas
authors.affiliation: Manchester Royal Eye Hospital, Central Manchester University Hospitals, NHS Foundation Trust, Manchester, UK.|Centre for Hearing and Vision Research, Medical School, University of Manchester, Manchester, UK.|Heriot-Watt University, Edinburgh, United Kingdom.
authors.forename: Tariq
authors.initials: T
authors.lastname: Aslam
mesh_terms: D000465:Algorithms; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D007223:Infant; D007231:Infant, Newborn; D015588:Observer Variation; D010781:Photography; D015203:Reproducibility of Results; D012171:Retinal Vessels / Q000473:pathology*; D012178:Retinopathy of Prematurity / Q000175:diagnosis*; D012984:Software
keywords: image analysis; retinopathy of prematurity; semi-automated analysis; tortuosity