Phillip J Buckhurst1, Shehzad A Naroo1, Leon N Davies1, Sunil Shah1, Hetal Buckhurst1, Alec Kingsnorth1, Tom Drew1, James S Wolffsohn2. 1. 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. 2. 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.
Abstract
PURPOSE: To assess the validity and repeatability of the Aston Halometer. SETTING: University clinic, United Kingdom. DESIGN: 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. CONCLUSION: 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.
PURPOSE: To assess the validity and repeatability of the Aston Halometer. SETTING: University clinic, United Kingdom. DESIGN: 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. CONCLUSION: 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.