May 2005
Volume 46, Issue 13
Free
ARVO Annual Meeting Abstract  |   May 2005
Diameter/Area of the Standardized Optic Disc and Accurate Scaling in Retinal Images
Author Affiliations & Notes
  • J.A. Elledge
    Ophthalmology and Vis Sci, University of Wisconsin, Madison, WI
  • M.D. Davis
    Ophthalmology and Vis Sci, University of Wisconsin, Madison, WI
  • L.D. Hubbard
    Ophthalmology and Vis Sci, University of Wisconsin, Madison, WI
  • J.L. Reimers
    Ophthalmology and Vis Sci, University of Wisconsin, Madison, WI
  • C.A. Fink
    Ophthalmology and Vis Sci, University of Wisconsin, Madison, WI
  • D.G. Hafford
    Ophthalmology and Vis Sci, University of Wisconsin, Madison, WI
  • R.A. Susman
    Ophthalmology and Vis Sci, University of Wisconsin, Madison, WI
  • Footnotes
    Commercial Relationships  J.A. Elledge, None; M.D. Davis, None; L.D. Hubbard, None; J.L. Reimers, None; C.A. Fink, None; D.G. Hafford, None; R.A. Susman, None.
  • Footnotes
    Support  NIH Contracts EY02130 & EY72145
Investigative Ophthalmology & Visual Science May 2005, Vol.46, 2583. doi:
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      J.A. Elledge, M.D. Davis, L.D. Hubbard, J.L. Reimers, C.A. Fink, D.G. Hafford, R.A. Susman; Diameter/Area of the Standardized Optic Disc and Accurate Scaling in Retinal Images . Invest. Ophthalmol. Vis. Sci. 2005;46(13):2583.

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

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Abstract

Abstract: : Purpose: To compare classic and modern assumptions regarding disc dimensions, as documented in fundus photos, and explore their impact on linear and area measurements of abnormalities. To investigate distance from disc center to macular center (D–M) as a potential calibration factor. Methods: Long–standing clinical convention assumed that the disc is 1.5mm/1500µm. Historical studies accepted this figure, and pragmatically established nearly identical standardized disc diameters (DD) for application to slides from the Zeiss FF2–4 fundus camera: ETDRS/AREDS, 4.7 mm; MPS, 4.5 mm. Although the standard DD as an established unit remains unchanged by our measurement of a more recent sample, careful observation by other studies (e.g., Jonas JB et al., 1988; Mansour AM, 1990) indicated 1 DD = 1.8–1.9 mm would be a more accurate equivalence in vivo. As modern technology required a more accurate equivalence, various modern digital camera systems have now adopted 1DD=1.8mm as their equivalence. Results: Measurement of 174 eyes (87 subjects) on Zeiss photos yielded tentative results of 1 DD=4.6 mm and average D–M=2.54 DD. Across subjects, measured D–M was half as variable as measured DD proportionately. Having refined our technique, we are re–measuring the sample and will present final results. Following are in vivo dimensions and areas for various features under different assumptions: Assumption Equivalence 125µm druse 1 DA zone of DME "Classic" 1 DD= 1.5mm 125 µm 1.77 mm2 "Modern" 1 DD= 1.8mm 150 µm 2.54 mm2 Best Estimate 1 DD ∼ 1.9mm ∼158 µm ∼2.84 mm2 Conclusions: Although the standardized DD remains an absolute and reliable measure, its equivalence in mm/µm varies according to classic, modern, or best estimate assumptions. Confusion about underlying assumptions can result in uncertainty and perhaps unintentional differences – e.g., the Stratus OCT 6 mm macular grid appears to be actually that, while the ETDRS macular grid with 2DD diameter is 7.2 mm in some digital camera systems.

Keywords: retina • anatomy • imaging/image analysis: clinical 
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