May 2004
Volume 45, Issue 13
Free
ARVO Annual Meeting Abstract  |   May 2004
Perimetric Indices representing visual loss for sensitivities in linear units
Author Affiliations & Notes
  • M.W. Dul
    Clinical Sciences, SUNY State College of Optometry, New York, NY
  • R. Malik
    Glaucoma Research Unit, Moorfields Eye Hospital, London, United Kingdom
  • W.H. Swanson
    Clinical Sciences, SUNY State College of Optometry, New York, NY
  • Footnotes
    Commercial Relationships  M.W. Dul, None; R. Malik, None; W.H. Swanson, None.
  • Footnotes
    Support  Glaucoma Institute, SUNY; Guide Dogs for the Blind, Grant OR2002–16e; NIH Grant EY07716
Investigative Ophthalmology & Visual Science May 2004, Vol.45, 3290. doi:
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      M.W. Dul, R. Malik, W.H. Swanson; Perimetric Indices representing visual loss for sensitivities in linear units . Invest. Ophthalmol. Vis. Sci. 2004;45(13):3290.

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

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Abstract

Abstract: : Purpose: Recent studies have utilized linear units for perimetric sensitivity in specific regions of the visual field, but global indices have yet to be developed in linear units. We devised and evaluated global linear indices, using macular perimetry to take advantage of relatively low normal within–subject and between–subject variability. Methods: We tested one eye each in a group of 11 patients with stable, advanced glaucoma and in a control group of 10 age–similar normal volunteers. Differential light sensitivities (DLS) were assessed using the Full Threshold (FT) and SITA Standard (SS) algorithms with the Humphrey Field Analyzer 10–2 pattern. All tests were repeated twice within three weeks. All sensitivities were converted to linear DLS units (1/Lambert) before computing global indices. The Mean Defect Index (MDI) was computed from the arithmetic mean of all sensitivities. The Diffuse Loss Index (DLI) was computed from the average of sensitivities at the 10 most sensitive points. The Pattern Variation Index (PVI) was defined as the DLI divided by the MDI. A one–tailed 95% confidence limit was used to define abnormality with each test considered separately. Results: The MDI for the control group was in the range 478–1845(FT) or 620–2112(SS) and for patients was 33–780(FT) or 27–915(SS), with 19(FT) or 20(SS) patients flagged as abnormal. DLI for controls was 845–2785(FT) or 900–2740(SS) and in glaucoma subjects was 182–1559(FT) or 151–1659(SS), with 14(FT) or 15(SS) patients flagged as abnormal. PVI had a range of 1.5–2.0(FT) or 1.3–1.8(SS) in controls and 2.0–6.6(FT) or 1.9–6.4(SS) in patients, with all 22 tests flagged as abnormal (FT and SS). The mean test–retest variability across individual locations was 54(FT & SS), in damaged locations compared to 486(FT) and 335(SS) in normal locations (t > 7, p < 0.001, FT and SS). Test–retest variability for the global indices averaged 70(FT), 40(SS) for MDI, 200(FT), 140(SS) for DLI and 0.26(FT), 0.28(SS) for PVI. Conclusions: The linear global indices gave similar results for both Full Threshold and SITA algorithms. Mean Test–retest variability for these indices was lower in damaged vs. normal areas. The Pattern Variation Index was found to be a sensitive index with low variability.

Keywords: perimetry • visual fields 
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