Abstract

SO.16.08

Quantification of perimetric results – a volumetric approach

Ulrich Schiefer1, Sandra Frick1, Jukka Nevalainen1,2, Julia Grobbel1, Elke Krapp1, R. Weleber3, J. Dietzsch1
1Department / Forschungsinstitut für Augenheilkunde, Universität Tübingen, Deutschland; 2University Eye Hospital Oulu, Finland; 3Casey Eye Institute, Oregon Health & Science University, Portland, OR, USA

Objective: The quantification of perimetric results is of major importance for the rating of the degree of visual field loss and for evaluating its change over time in any kind of visual pathway lesion. The purpose of this study was to develop a volumetric approach that can be utilized for the quantitative analysis of visual field loss with relation to an age-corrected normative hill of vision.
Methods: Eighty-one normal subjects, aged from 10 to 79 years were enrolled in this study, which was performed on the new Octopus 900 perimeter (HAAG-STREIT Inc., Koeniz, Switzerland). Eighty-six static stimuli (Goldmann size III = 26´) up to a maximal eccentricity of 80 degrees, with a condensation towards the visual field centre, were presented on a homogeneous background under photopic conditions (luminance level 10 cd/square meter). A fast thresholding algorithm (GATE: initial step size of 4 dB and at least one reversal) was used. The volumetric analysis – in the unit of dB x square degrees – was based on a smooth mathematical model and a triangulation routine that was related to the 86 test locations.
Results: The model fit was satisfactory (R2 = 0.72 dB2). The residual standard deviation over the entire 80 degree visual field amounted to 2.52 dB. The visual field volumes for the examined normal cohort ranged from 255,219 dB x square degrees at the age of 10 years to 198,651 dB x square degrees at the age of 80 years. The volume of the hill of vision reached its maximum of 255,989 dB x square degrees at the age of 17.3 years and declined continuously thereafter.
Conclusions: The volumetric approach allows for a quantification and follow-up of visual field results with relation to an age-corrected (80 degree) hill of vision. A slightly modified method can also be utilized for a quantitative scotoma analysis that is almost independent of the test point arrangement! It can be related to the entire visual field (TLV = „total loss volume“) or to selected sub-regions of the visual field (RLV = „regional loss volume“).

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