June 2017
Volume 58, Issue 8
Open Access
ARVO Annual Meeting Abstract  |   June 2017
Quantifying the signal/noise ratio with perimetric stimuli optimised to probe changing spatial summation in glaucoma
Author Affiliations & Notes
  • Lindsay Rountree
    School of Optometry and Vision Sciences, Cardiff University, Cardiff, United Kingdom
  • Padraig Joseph Mulholland
    Optometry and Vision Science Research Group, School of Biomedical Sciences, Ulster University, Coleraine, N. Ireland, United Kingdom
    National Institute for Health Research (NIHR) Biomedical Research Centre, Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology, London, United Kingdom
  • Roger S Anderson
    Optometry and Vision Science Research Group, School of Biomedical Sciences, Ulster University, Coleraine, N. Ireland, United Kingdom
    National Institute for Health Research (NIHR) Biomedical Research Centre, Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology, London, United Kingdom
  • James E Morgan
    School of Optometry and Vision Sciences, Cardiff University, Cardiff, United Kingdom
  • David Garway-Heath
    National Institute for Health Research (NIHR) Biomedical Research Centre, Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology, London, United Kingdom
  • Tony Redmond
    School of Optometry and Vision Sciences, Cardiff University, Cardiff, United Kingdom
  • Footnotes
    Commercial Relationships   Lindsay Rountree, None; Padraig Mulholland, Heidelberg Engineering (R); Roger Anderson, Heidelberg Engineering (R); James Morgan, None; David Garway-Heath, Centervue (R), Heidelberg Engineering (F), Heidelberg Engineering (R), Moorfields MDT (P), Topcon (F); Tony Redmond, Heidelberg Engineering (F)
  • Footnotes
    Support  College of Optometrists postgraduate scholarship
Investigative Ophthalmology & Visual Science June 2017, Vol.58, 2852. doi:
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      Lindsay Rountree, Padraig Joseph Mulholland, Roger S Anderson, James E Morgan, David Garway-Heath, Tony Redmond; Quantifying the signal/noise ratio with perimetric stimuli optimised to probe changing spatial summation in glaucoma. Invest. Ophthalmol. Vis. Sci. 2017;58(8):2852.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose : Guided by changes in spatial summation in glaucoma, we undertook a cross-sectional prospective study to compare disease signal, response variability, and signal/noise ratio (SNR) between perimetric stimuli varying in area, contrast, and both simultaneously, in patients with glaucoma and age-similar healthy controls.

Methods : Participants were 30 glaucoma patients (median [interquartile range] age: 70.4 years [66.2, 73.5], MD: -4.04dB [-9.65, -2.85]) and 20 controls (age: 69.3 years [66.1, 77.8], MD +0.38dB [-0.36, +0.91]). Using a 3-stage approach (1: staircase procedure; 2: short Method of Constant Stimuli (MOCS, 180 presentations); 3: extended MOCS (640 presentations)), threshold (50% seen) and response variability (slope) were measured for 200ms achromatic spot stimuli, presented at 4 diagonal locations (9.9° from fixation). Stimuli were: A - fixed contrast (ΔI: 0.5, starting within Ricco’s area), varying in area; C1 - fixed area (0.02deg2, within Ricco’s area), varying in contrast; AC - varying in both area and contrast simultaneously (starting within Ricco’s area); C2 - fixed area (0.15deg2), equivalent to Goldmann III, varying in contrast. Stimuli were defined by a common scale (energy: luminance x area x duration). Step size and visibility were equated across all stimulus forms. Total deviation (TD, calculated from healthy subjects for each stimulus form), slope, and SNR (TD/slope) were compared between stimuli per hemifield in three TD strata (upper, middle, lower, according to TD for the C2 stimulus).

Results : Overall, the greatest disease signal was found with A and AC stimuli (Fig.1A). Response variability was least dependent on depth of defect with the A stimulus, and most for the C2 stimulus (Fig.1B). The SNR was greatest for the A stimulus, and the difference from that for the C2 stimulus was statistically significant in the superior hemifield in the middle (p=0.04) and lower (p=0.049) strata (Fig.2).

Conclusions : Area-modulated stimuli likely offer benefits for measuring glaucomatous changes in spatial summation, in the form of greater disease signal and least dependence on depth of defect than conventional fixed-area, contrast-modulated stimuli.

This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.

 

(A) TD for each stimulus form as a function of C2 TD; (B) Response variability as a function of stimulus-specific TD; superior hemifield.

(A) TD for each stimulus form as a function of C2 TD; (B) Response variability as a function of stimulus-specific TD; superior hemifield.

 

SNR across three TD (C2) strata in superior and inferior hemifields

SNR across three TD (C2) strata in superior and inferior hemifields

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