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Agnes Yiu Jeung Choi, Lisa Nivison-Smith, Nagi Assaad, Sieu K Khuu, Michael Kalloniatis; Spatial summation across the 10-2 visual field in normals and age-related macular degeneration. Invest. Ophthalmol. Vis. Sci. 2016;57(12):No Pagination Specified.
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© ARVO (1962-2015); The Authors (2016-present)
The Goldmann (G) size III stimulus of the Humphrey Visual Field Analyzer (HVFA) is routinely used to assess contrast sensitivity across the visual field. However, reports on spatial summation characteristics of the 30-2 paradigm suggest that GIII tests outside complete spatial summation and using this stimulus may result in smaller differences in contrast thresholds between normal and those with ocular disease. The 10-2 paradigm is a highly relevant test for ocular diseases affecting the central 20-degree field but the spatial summation characteristics of this paradigm including the location of the critical area (Ac) and slope of partial summation are unknown. Thus we investigated spatial summation changes in the 10-2 paradigm between normal and those with age-related macular degeneration (AMD).
We measured thresholds for one eye from 37 normal subjects aged 20-62 years (mean: 36±11 years) using the HVFA 10-2 full threshold paradigm with GI to GV stimuli. Spatial summation curves were plotted for each test location by fitting data with a two-line fit and derived Ac and slope of partial summation. After verifying Ac and partial summation slope do not change with age, we converted subject data to 50-year-old equivalent using published and calculated location specific decade correction factors. We applied similar procedures to 11 patients with intermediate AMD (range: 61-80 years; mean: 71±6 years) and compared spatial summation characteristics of this group to normative data.
Normative Ac was established for the 10-2 paradigm and found to increase with eccentricity, consistent with previous studies using other test paradigms. GIII stimulus always exceeded Ac and tested visual function within various stages of partial summation across the 10-2 paradigm. A bigger difference in contrast thresholds was generally observed between normal and AMD patients when using a test stimulus at or within complete spatial summation (GI or GII).
Normative Ac values indicate that GI and GII test sizes operate within complete spatial summation while the standard GIII stimulus operates across a range of partial summation in the HVFA10-2 paradigm. Our results suggest that using test stimuli at or within complete spatial summation reveals a greater loss compared to the standard GIII stimulus in the 10-2 paradigm in patients with intermediate AMD.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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