title: Tablet App halometer for the assessment of dysphotopsia.
abstract: OBJECTIVE
  To assess the validity and repeatability of the Aston Halometer.
  
  
  METHODS
  University clinic, United Kingdom.
  
  
  METHODS
  Prospective, repeated-measures experimental study.
  
  
  METHODS
  The halometer comprises a bright light-emitting-diode (LED) glare source in the center of an iPad4. Letters subtending 0.21° (~0.3 logMAR) were moved centrifugally from the LED in 0.05 degree steps in 8 orientations separated by 45 degrees for each of 4 contrast levels (1000, 500, 100, and 25 Weber contrast units [Cw]) in random order. Bangerter occlusion foils were inserted in front of the right eye to simulate monocular glare conditions in 20 subjects (mean age 27.7 ± 3.1 years). Subjects were positioned 2 meters from the screen in a dark room with the iPad controlled from an iPhone via Bluetooth operated by the researcher. The C-Quant straylight meter was also used with each of the foils to measure the level of straylight over the retina. Halometry and straylight repeatability was assessed at a second visit.
  
  
  RESULTS
  Halo size increased with the different occlusion foils and target contrasts (F = 29.564, P < .001) as expected and in a pattern similar to straylight measures (F = 80.655, P < 0.001). Lower contrast letters showed better sensitivity but larger glare-obscured areas, resulting in ceiling effects caused by the screen's field-of-view, with 500 Cw being the best compromise. Intraobserver and interobserver repeatability of the Aston Halometer was good (500Cw: 0.84 to 0.93 and 0.53 to 0.73) and similar to the straylight meter.
  
  
  CONCLUSIONS
  The halometer provides a sensitive, repeatable way of quantifying a patient-recognized form of disability glare in multiple orientations to add objectivity to subjectively reported discomfort glare.
authors.affiliation: From the School of Health Professions (P.J. Buckhurst, H. Buckhurst), University of Plymouth, Plymouth, United Kingdom, Ophthalmic Research Group (Naroo, Davies, Shah, Kingsnorth, Drew, Wolffsohn), Life and Health Sciences, Aston University, Birmingham, United Kingdom, Midland Eye (Shah), Solihull, United Kingdom.
authors.forename: Phillip J
authors.initials: PJ
authors.lastname: Buckhurst
authors.affiliation: From the School of Health Professions (P.J. Buckhurst, H. Buckhurst), University of Plymouth, Plymouth, United Kingdom, Ophthalmic Research Group (Naroo, Davies, Shah, Kingsnorth, Drew, Wolffsohn), Life and Health Sciences, Aston University, Birmingham, United Kingdom, Midland Eye (Shah), Solihull, United Kingdom.
authors.forename: Shehzad A
authors.initials: SA
authors.lastname: Naroo
authors.affiliation: From the School of Health Professions (P.J. Buckhurst, H. Buckhurst), University of Plymouth, Plymouth, United Kingdom, Ophthalmic Research Group (Naroo, Davies, Shah, Kingsnorth, Drew, Wolffsohn), Life and Health Sciences, Aston University, Birmingham, United Kingdom, Midland Eye (Shah), Solihull, United Kingdom.
authors.forename: Leon N
authors.initials: LN
authors.lastname: Davies
authors.affiliation: From the School of Health Professions (P.J. Buckhurst, H. Buckhurst), University of Plymouth, Plymouth, United Kingdom, Ophthalmic Research Group (Naroo, Davies, Shah, Kingsnorth, Drew, Wolffsohn), Life and Health Sciences, Aston University, Birmingham, United Kingdom, Midland Eye (Shah), Solihull, United Kingdom.
authors.forename: Sunil
authors.initials: S
authors.lastname: Shah
authors.affiliation: From the School of Health Professions (P.J. Buckhurst, H. Buckhurst), University of Plymouth, Plymouth, United Kingdom, Ophthalmic Research Group (Naroo, Davies, Shah, Kingsnorth, Drew, Wolffsohn), Life and Health Sciences, Aston University, Birmingham, United Kingdom, Midland Eye (Shah), Solihull, United Kingdom.
authors.forename: Hetal
authors.initials: H
authors.lastname: Buckhurst
authors.affiliation: From the School of Health Professions (P.J. Buckhurst, H. Buckhurst), University of Plymouth, Plymouth, United Kingdom, Ophthalmic Research Group (Naroo, Davies, Shah, Kingsnorth, Drew, Wolffsohn), Life and Health Sciences, Aston University, Birmingham, United Kingdom, Midland Eye (Shah), Solihull, United Kingdom.
authors.forename: Alec
authors.initials: A
authors.lastname: Kingsnorth
authors.affiliation: From the School of Health Professions (P.J. Buckhurst, H. Buckhurst), University of Plymouth, Plymouth, United Kingdom, Ophthalmic Research Group (Naroo, Davies, Shah, Kingsnorth, Drew, Wolffsohn), Life and Health Sciences, Aston University, Birmingham, United Kingdom, Midland Eye (Shah), Solihull, United Kingdom.
authors.forename: Tom
authors.initials: T
authors.lastname: Drew
authors.affiliation: From the School of Health Professions (P.J. Buckhurst, H. Buckhurst), University of Plymouth, Plymouth, United Kingdom, Ophthalmic Research Group (Naroo, Davies, Shah, Kingsnorth, Drew, Wolffsohn), Life and Health Sciences, Aston University, Birmingham, United Kingdom, Midland Eye (Shah), Solihull, United Kingdom. Electronic address: j.s.w.wolffsohn@aston.ac.uk.
authors.forename: James S
authors.initials: JS
authors.lastname: Wolffsohn
mesh_terms: D000328:Adult; D034201:Computers, Handheld; D003941:Diagnostic Techniques, Ophthalmological / Q000295:instrumentation*; D004185:Disability Evaluation; D005260:Female; D019466:Glare / Q000009:adverse effects; D006801:Humans; D008297:Male; D015588:Observer Variation; D011446:Prospective Studies; D015203:Reproducibility of Results; D012542:Scattering, Radiation; D012680:Sensitivity and Specificity; D014786:Vision Disorders / Q000175:diagnosis* / Q000209:etiology