June 2015
Volume 56, Issue 7
Free
ARVO Annual Meeting Abstract  |   June 2015
Possible Causes of “Green Disease”, Glaucomatous Damage Missed by Conventional Analysis of Peripapillary Frequency Domain OCT Disc Scans.
Author Affiliations & Notes
  • Kevin K Ma
    College of Physicians & Surgeons, Columbia University, New York, NY
  • Dana Blumberg
    Ophthalmology, Columbia University, New York, NY
  • Noelle Pensec
    Ophthalmology, Columbia University, New York, NY
  • Diane Wang
    Psychology, Columbia University, New York, NY
  • Ali S Raza
    Psychology, Columbia University, New York, NY
    Neurobiology and Behavior, Columbia University, New York, NY
  • Lola Grillo
    College of Physicians & Surgeons, Columbia University, New York, NY
  • Donald Hood
    Psychology, Columbia University, New York, NY
    Ophthalmology, Columbia University, New York, NY
  • Footnotes
    Commercial Relationships Kevin Ma, None; Dana Blumberg, None; Noelle Pensec, None; Diane Wang, None; Ali Raza, None; Lola Grillo, None; Donald Hood, Topcon (F)
  • Footnotes
    Support None
Investigative Ophthalmology & Visual Science June 2015, Vol.56, 4547. doi:
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      Kevin K Ma, Dana Blumberg, Noelle Pensec, Diane Wang, Ali S Raza, Lola Grillo, Donald Hood; Possible Causes of “Green Disease”, Glaucomatous Damage Missed by Conventional Analysis of Peripapillary Frequency Domain OCT Disc Scans.. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):4547.

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

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Abstract

Purpose: To determine why glaucomatous eyes with an abnormal optic nerve cup-to-disc ratio (CDR) and corresponding visual field (VF) defect can show a normal peripapillary retinal nerve fiber layer (RNFL) thickness on frequency domain optical coherence tomography (fdOCT).

Methods: A glaucoma specialist identified 12 eyes from 12 consecutive patients (66 to 85 years of age) with abnormal CDR and a corresponding 24-2 VF defect, but normal peripapillary RNFL thickness (within the 95% confidence limit) on the commercial fdOCT disc report (Cirrus, Carl Zeiss Meditec). Macular cube scans were also obtained. Using a manually corrected segmentation algorithm, the RNFL and retinal ganglion cell plus inner plexiform layer (RGC+) probability maps, as well as macular B-scans, were generated and compared to the disc and VF data. To test the hypothesis that damage may have been missed due to a relatively thicker baseline RNFL, a ratio of quadrant RNFL thicknesses {superior (S) + inferior (I)}/nasal (N), was calculated for each eye and compared to controls.

Results: The eyes fell into one or more of the following categories: segmentation errors (2 eyes), early local damage missed/underestimated on the fdOCT report (3 eyes), coexisting macular pathology (4 eyes; epiretinal membrane (2), branch retinal vein occlusion (1) and macular edema (1)), subtle local thinning (SLT: 4 eyes), and a thicker baseline RNFL (2 eyes). In the latter case, the RNFL of the nasal quadrant was thicker than controls, as confirmed by a significantly smaller (S+I)/N ratio. All 4 eyes with SLT had subtle peripapillary RNFL thinning as compared to the opposite eye, in the disc region near 12 or 6 o’clock in the quadrant of question.

Conclusions: OCT can miss marked glaucomatous damage due to segmentation errors, subtle local damage, underlying macular pathology, and thicker RNFL thickness when healthy. A comparison of RNFL thickness relative to the nasal quadrant might help identify the latter group of eyes, while a closer examination of OCT scans can help identify the former. The fact that subtle RNFL thinning occurred in the same disc locations for the 4 SLT eyes suggests an explanation. These disc locations receive significant input from regions that extend far beyond the region covered by the 24-2 VF, which might make the local defects seen on the 24-2 difficult to observe on OCT.

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