Abstract
Purpose: :
To model the "Hill of Vision" and develop metrics for use in diagnosis, characterization of defects, and as endpoints.
Methods: :
We measured differential luminance sensitivity (DLS) values out to 80° temporally with the GATE strategy (Schiefer et al, ARVO 2007 Program #4452), the Octopus 101 perimeter (Haag-Streit, Inc., Koeniz, Switzerland), and radially-oriented, centrally condensed grids of 187, 158, 143, 124, and 102 test locations. We tested 26 normal subjects and 250 patients with one or more grids over the past year. Seven normal subjects (20 to 38 years) were tested with at least two of these grids or static stimuli of both Goldmann size III (26') and size V (103') on a 10 cd/m² background. We modeled the Hill of Vision (HOV) using a flexible spline fit. The volume of the HOV was measured using a newly defined unit, the decibel-steradians (dB-sr). We compared the total volume of the HOV and Mean Sensitivity (MS) among the grids and between the two stimulus sizes.
Results: :
The HOV volume and MS did not differ among the grids. DLS values with the 103' stimulus size were 1 to 5 dB greater centrally and 7 to 13 dB greater peripherally than those with the size 26'. Respectively, the mean (±1 SD) MS and HOV volume and ranges were 23.5±0.9 dB and 62.8±4.3 (54.1-70.7) dB-sr for size III (n=31 eyes) and 29.6±1.4 dB and 88.9±5.4 (80.7-99.0) dB-sr for size V (n=30 eyes) stimuli. Test times for the five grids, respectively, averaged 23.1, 20.7, 19.1, 14.6, and 12.0 minutes for normals and from 1 to 6 minutes less for patients. Specific regions of the HOV can be selectively measured as additional endpoints.
Conclusions: :
Modeling of the HOV enables 3-D viewing and volumetric measurement of the sensitivity of the entire visual field and provides new insights into the topography of sensitivity in normal subjects and in disease. The size V stimulus provides greater dynamic range for clinical testing. Parameters from HOV modeling provide endpoints for diagnosis and clinical trials.
Keywords: perimetry • visual fields • imaging/image analysis: clinical