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Vera Maria Mönter,1,2 David Paul Crabb,2 Paul Habib Artes1 1. Ophthalmology and Visual Sciences, Dalhousie University & Capital Health, Halifax, Canada2. Department of Optometry and Visual Science, City University London, United Kingdom

Reclaiming the Periphery – Frequency-of-Seeing for Static Perimetry on Kinetically Estimated Isopters, in Patients with Glaucoma and Healthy Controls

PurposePeripheral vision is important for mobility, balance, and driving. It may also be relevant to clinical decisions in glaucoma (progression, structure/function relationships, monitoring of advanced damage). We are working towards an efficient approach for examining the entire visual field where kinetic stimuli are used to estimate a single mid-peripheral isopter, primarily as a “region of interest” within which static perimetry is most efficient. To combine static and kinetic measurements (stato-kinetic automated perimetry, SKAP), we need to understand how both types relate to each other.

MethodsVisual fields of 8 patients (median age, 60 yrs; MD: -7.2 dB) with glaucoma and 11 controls (39 yrs) were examined with an Octopus 900 perimeter controlled through the Open Perimetry Interface (Turpin et al, J Vis 2012)1. Kinetic stimuli (Goldmann III1e, 0.43°, 15 dB, speed 5°/sec) were presented along 16 meridians, in random order (Fig. 1). The median response to 3 presentations defined the isopter. Frequency-of-seeing (FOS) data were then obtained to static stimuli (duration: 200 ms), at 5 visual field locations on the kinetic isopter (10 presentation at each of 8 intensities). Psychometric functions were fitted with a probit model as well as with a non-parametric approach.2, 3

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ResultsAt visual field locations on the III1e isopter (15 dB), sensitivity to the static stimuli was lower than 15 dB [median (m): 11.7 dB, 95% CI: 11.3, 12.1 dB]. Differences between healthy observers and glaucoma patients were small (Fig. 2). Response variability at peripheral locations appeared much lower than expected for locations of the same sensitivity in the central visual field (Henson et al,4 Fig. 3).

ConclusionFast and reliable automated perimetry of the periphery is technically feasible, and efficient tests need to be developed. Such tests may help to address problems in glaucoma that have not been solved by focusing exclusively on the central 20% of the visual field. We are now investigating the hypothesis that the observed stato-kinetic dissociation is primarily due to the longer effective duration of the kinetic stimuli rather than their motion.

Fig 1a) Patient G (glaucoma). Goldmann III1e isopter (dark green line) estimated from the median of 3 responses (small black circles) along the 16 kinetic vectors (dotted grey lines). Individual 85% confidence intervals were estimated from the median absolute deviation (MAD) of all responses (faint green band). Normative data for this isopter (Vonthein et al.)5 are shown in light green. Coloured rings on the isopter depict locations at which FOS data were obtained for static stimuli. b-f) FOS curves. Numbers in circles indicate responses at each intensity; 10 stimuli were presented. Fits are shown for a general linear model (probit) and a non-parametric technique (modelfree, Zychaluk & Foster, 2009).

Fig 2 Sensitivity (50%-seeing point on FOS curve) to static stimuli of 200 ms duration, presented at points on the isopter estimated with a III1e (15 dB, grey line) kinetic stimulus moving at 5°/s. Colours identify location (Fig. 1), letters identify participants.

Fig 3 Sensitivity (50%-seeing point) and response variabilty (slope of FOS curve) in patients (red) and controls (green). Data by Henson et al. (2000) from the central visual field are shown for comparison (black). Upper- and lower-case letters identify patients and controls.

1. Turpin et al . (2012) The Open Per imetr y Interface . J Vis ion2. Zychaluk & Foster (2009) Model-free estimation. Atten Percept Psychophys 3. Marin-Franch et al. (2012) modelfree R-package. CRAN.R-Project.org4. Henson et al. (2000) Response variability in the visual field. IOVS5. Vonthein et al (2007) The normal ... isopter. Ophthalmology+ Pineles et al. (2006) Automated combined ... perimetry. Arch Ophth

References

Acknowledgments: Andrew Turpin (U Melbourne) and Alfred Wiederkehr (Haag-Streit AG) helped generously to get us going with an early version of the Octopus 900 Open Perimetry Interface. This work is supported by an unrestricted Project Grant from the Merck Investigator Studies Programme (DPC) and by research support from Haag-Streit International (Switzerland) to PHA & DPC. VMM was supported by the ARVO International Travel Grant. Author contact information: vera.monter.1@city.ac.uk, david.crabb.1@city.ac.uk, paul@dal.ca

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Figure 1

Sensitivity (dB)

Sensitivity (dB)

Examples (right side of poster) of kinetic isopters estimated in patients with glaucoma (top 3) and a patient with retinitis pigmentosa (bottom).

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