Validation of a method to measure light distortion surrounding a source of glare

Abstract

Our objective was to validate a new device dedicated to measure the light disturbances surrounding bright sources of light under different sources of potential variability. Twenty subjects were involved in the study. Light distortion was measured using an experimental prototype (light distortion analyzer, CEORLab, University of Minho, Portugal) comprising twenty-four LED arrays panel at 2 m. Sources of variability included: intrasession and intersession repeated measures, pupil size (3 versus 6 mm), defocus (+0.50 ) correction for the working distance, angular resolution (15 deg versus 30 deg), temporal stimuli presentation, and pupil size. Size, shape, location, and irregularity parameters have been obtained. At a low speed of presentation of the stimuli, changes in angular resolution did not have an effect on the results of the parameters measured. Results did not change with pupil size. Intensity of the central glare source significantly influenced the outcomes. Examination time was reduced by 30% when a 30 deg angular resolution was explored instead of 15 deg. Measurements were fast and repeatable under the same experimental conditions. Size and shape parameters showed the highest consistency, whereas location and irregularity parameters showed lower consistency. The system was sensitive to changes in the intensity of the central glare source but not to pupil changes in this sample of healthy subjects

Light distortion and spherical aberration for the accommodating and nonaccommodating eye

“…The authors suggested that larger pupils were associated with stronger disturbances, but pupil size by itself was found to be only moderately correlated with this worsening effect in those eyes presenting positive SA as a consequence of the surgical procedure. More recently, Ferreira-Neves et al 9 evaluating nonoperated eyes showed that changing the pupil size from 3 to 6 mm did not have a significant impact on LD in healthy subjects with pharmacologically paralyzed accommodation. At first, this seems to imply that pupil size has no significant effect on light disturbance and accommodation might be involved.…”

“…8 LD was analyzed with an experimental prototype, the LDA (CEORLab, University of Minho, Portugal), which provides a comprehensive number of metrics to characterize the condition, and proved to be robust in measuring NVD in young healthy eyes and also in elderly patients. 3,8,9 It consists of an electronic black board with a central light source (LED) surrounded by 240 small LED sources distributed in 24 semimeridians with a minimum angular separation of 15 deg. In this experiment, an angular separation of 30 deg was considered to shorten the exam time without significant loss of information.…”

“…In this experiment, an angular separation of 30 deg was considered to shorten the exam time without significant loss of information. 9 Figure 1 (left) shows the layout arrangement of the central white LEDs and the surrounding smaller white LEDs. The technical specifications of the LEDs can be consulted in previously published work from Linhares et al 8 The subject was at a distance of 2.0 m in a darkened room and was instructed to always fixate on the central LED while doing the measurements.…”

Corneal Aberrations, Contrast Sensitivity, and Light Distortion in Orthokeratology Patients: 1-Year Results

“…It consists of an array of 240 1 mm wide LEDs distributed radially at 15° intervals over 160 mm, with a linear separation of 10 mm around a central 5 mm white LED that acts as glare source, as previously described [17, 18, 20]. The system is controlled by a custom-made software that interfaces with the patient to detect the peripheral stimuli seen and discriminate them from those hidden by the central glare source.…”

“…We use a physical display to present the stimuli as this allows us to have a wider dynamic range of luminance from the main glare source and the detection peripheral stimuli [20] and this instrument has been shown to be consistent with [17] and sensitive to changes in higher-order aberrations (HOA) artificially induced [18]. …”