April 2010
Volume 51, Issue 13
Free
ARVO Annual Meeting Abstract  |   April 2010
Detecting Glaucomatous Changes Using Only One Optic Nerve Head Scan Per Exam
Author Affiliations & Notes
  • M. Balasubramanian
    Hamilton Glaucoma Center, Department of Ophthalmology,
    UCSD, San Diego, California
  • C. Bowd
    Hamilton Glaucoma Center, Department of Ophthalmology,
    UCSD, San Diego, California
  • D. J. Kriegman
    Computer Science & Engineering,
    UCSD, San Diego, California
  • R. N. Weinreb
    Hamilton Glaucoma Center, Department of Ophthalmology,
    UCSD, San Diego, California
  • P. A. Sample
    Hamilton Glaucoma Center, Department of Ophthalmology,
    UCSD, San Diego, California
  • L. M. Zangwill
    Hamilton Glaucoma Center, Department of Ophthalmology,
    UCSD, San Diego, California
  • Footnotes
    Commercial Relationships  M. Balasubramanian, None; C. Bowd, Lace Elettronica, F; D.J. Kriegman, None; R.N. Weinreb, Carl Zeiss Meditec, Inc., F; Heidelberg Engineering, GmbH, F; Novartis, F; Optovue, Inc., F; Topcon Medical Systems, Inc., F; Alcon Laboratories, Inc., C; Allergan, Inc., C; Carl Zeiss Meditec, Inc., C; Glaxo, C; Optovue, Inc., C; Pfizer, Inc., C; Topcon Medical Systems, Inc., C; P.A. Sample, Carl Zeiss Meditec, F; Haag-Streit, F; Welch-Allyn, F; L.M. Zangwill, Topcon Medical Systems, Inc., F; Optovue, Inc., F; Carl Zeiss Meditec, Inc., F; Heidelberg Engineering, GmbH, F.
  • Footnotes
    Support  NEI EY11008 (LMZ), EY08208 (PAS), and participant retention incentive grants in the form of glaucoma medication at no cost from Alcon Laboratories Inc, Allergan, Pfizer Inc, Merck Inc, and Santen Inc.
Investigative Ophthalmology & Visual Science April 2010, Vol.51, 2723. doi:
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    • Get Citation

      M. Balasubramanian, C. Bowd, D. J. Kriegman, R. N. Weinreb, P. A. Sample, L. M. Zangwill; Detecting Glaucomatous Changes Using Only One Optic Nerve Head Scan Per Exam. Invest. Ophthalmol. Vis. Sci. 2010;51(13):2723.

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

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Abstract

Purpose: : To evaluate a new retinal reflectance based method to detect glaucomatous changes using only 1 HRT optic disk scan per follow-up exam.

Methods: : Each HRT scan L is modeled as L = I R cos(k) using a surface reflectance model; I is the incident illumination component; R is a reflectance map that describes surface reflectivity of the retina; and k is the incident angle between the laser light beam and retinal surface orientation. The reflectance R is less dependent on the incident angle k and likely has lower intra/inter-exam variability than the HRT image L. So, we used reflectance maps to detect glaucomatous changes. For each HRT exam, 1 of 3 scans was chosen and its reflectance map R computed using a Homomorphic filter (Oppenheim A, et al, IEEE Proc. 1968). At each superpixel (4×4 neighboring locations), change in reflectance from baseline to follow-up was estimated using a two-sample t-test. To identify locations with significant reduction in retinal height (red-pixels), p-value cutoffs were estimated at a false positive rate of 5% using the false discovery rate control method (FDR). For each follow-up, the ratio of total no. of red-pixels within the optic disk to disk size (red-pixels ratio) was calculated. Progression was defined as the presence of one or more follow-ups with red-pixels ratio > false positive rate. The results were compared to TCA with FDR (Balasubramanian M, et al, IOVS 2009; 50: ARVO E-Abstract 2573). 167 participants (246 eyes) with ≥4 HRT-II exams from the UCSD Diagnostic Innovations in Glaucoma Study (DIGS) were included; 36 eyes progressed by stereophotographs or showed likely progression on SAP Guided Progression Analysis (progressors). All other eyes were considered to be non-progressing. Specificities were estimated in 21 longitudinal normal eyes (normals).

Results: : The diagnostic accuracies of the reflectance based method / TCA with FDR were: 64% / 69% sensitivity in progressors; 74% / 53% specificity in non-progressors; and 100% / 90% specificity in normals, respectively.

Conclusions: : The reflectance based method using 1 scan per exam provides high specificity and moderate sensitivity comparable to TCA with FDR that uses 3 scans per exam. Because reflectance maps are less dependent on variability in retinal surface orientation, these results suggest that it is possible to achieve comparable diagnostic power from just 1 scan per exam. The proposed method can be extended to detect glaucomatous changes from stereophotographs and spectral domain optical coherence tomography exams typically with 1 scan per exam.

Keywords: imaging/image analysis: clinical • computational modeling 
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