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Editors Selection IGR 7-3

Perimetry: Structure-function relation

Comment by William Swanson on:

51828 A novel distribution of visual field test points to improve the correlation between structure-function measurements, Asaoka R; Russell RA; Malik R et al., Investigative Ophthalmology and Visual Science, 2012; 53: 8396-8404

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A novel distribution of visual field test points to improve the correlation between structure-function measure ments Asaoka R, Russell RA, Malik R, Crabb DP, Garway-Heath DF Investigative Ophthalmology and Visual Science 2012; 53: 8396-8404 Kinetic perimetry adapts to each patient, varying the locations tested and stimulus size. Static automated perimetry (SAP) instead uses a fixed set of test locations for all subjects. In the early days of SAP, test locations were more biologically inspired, (such as the G1 program) with closer spacing of locations in the macula and greater spacing more peripherally. However, regular grids allowed production of grayscale plots, and they became the convention. Some authors refer to SAP as 'standard' automatic perimetry, but the choices for stimuli and locations do not represent a scientific standard. Computers are far more sophisticated now, so regular grids are no longer needed for grayscale plots. The limitations of regular grids are apparent in structure-function studies, where some sectors of the optic nerve are represented by just a few visual field locations, while others are represented by many more locations. These authors used both 24-2 locations and disc-centered field locations, and combined these to assess strength of structure-function correlations for 12 different sectors of the optic disc. They found a subset of 40 locations that gave stronger structure-function correlations than the 24-2. Recent studies have found that macular damage is not uncommon in patients with glaucoma, but only four locations in the 24-2 test this region. The authors show that alternative test locations can increase the number of test locations in the macula, without losing ability to detect more peripheral defects. The authors note that they used an average structure-function map, yet the map for individuals will vary from this due to axial length, optic nerve tilt, and distance from optic nerve to fovea. The use of individualized maps could lead to the use of individualized test locations. This study is an important step towards a new perimetry for the 21^st century.

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