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Report
SPECTRALIS® Glaucoma Module
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Clinical Mismatch
Mismatch between clinically
visible disc margin &
SD-OCT-based disc margin
SD-OCT BMO
Clinically Visible
Optic Disc Margin
Image Courtesy Dr. Balwantray C. Chauhan, Halifax, Canada and
Dr. Claude F. Burgoyne, Portland, USA.
Variable Rim Tissue
 Internally oblique
 Externally oblique
 Non-oblique
BMO
Image Courtesy Dr. B.C. Chauhan, Halifax, Canada.
Reis et al. Ophthalmology 119:738-747,2012.
Clinical
disc margin
Clinical Disc Margin
Conclusion
 The clinical optic disc margin is hard to identify
 In practice the clinician is looking at 3 different tissues when defining
the disc margin
 BMO (1), RPE tips (endings; 2), some aspect of border tissue of Elschnig (3)
 The clinical disc margin is inconsistent as an anatomical landmark
for the outer border of the rim
 Each individual ONH can have regions of internally and / or externally
oblique border tissues
Overestimation of Rim Tissue
Consequences
 Inconsistent definition of the
disc margin can mean an
underestimation of rim tissue.
 Using Bruch´s membrane opening (BMO)
DM
BMO
Image Courtesy Dr. B.C. Chauhan, Halifax, Canada.
as a stable landmark provides a more
accurate measurement of the ONH rim tissue.
Invisible BMO
 Bruch's Membrane Opening is a consistent landmark,
but it is usually clinically and photographically invisible.
BMO
Image Courtesy Dr. B.C. Chauhan, Halifax, Canada.
Geometric Orientation
 Even if BMO is used as a stable landmark by SD-OCT,
we still need to measure the neuroretinal rim in the correct
geometric orientation.
BMO-MRW
Reis et al. Invest Ophthalmology Vis Sci. 53: 1852-1860, 2012.
Basic Information
Correct Rim Measurement
 Neuroretinal rim measurement
from BMO to nearest point on
internal limiting membrane (ILM)
BMO-MRW
 Shortest distance measurement
 Quantification of perpendicular
cross section of nerve fibers
exiting the eye
Reis et al. Invest Ophthalmology Vis Sci. 53: 1852-1860, 2012.
 Taking into account their varying
trajectory at all 48 points of
measurement
Cross Section of RNF
Current Reality
 Current sectorial analysis
is made with fixed horizontal
and vertical axes on the image.
AIF Horizontal (N/T) Axis
AIF Vertical (S/I) Axis
Acquired Image Frame (AIF)
Range of Variability of FoBMO Axes
 Inter-individual variability in the axis connecting the
Fovea and Bruch’s Membrane Opening (BMO) center
<
+ 2°
to
- 18°
*
* Examples taken from the HDEng
SPECTRALIS normative data collection
Anatomically Normalized Eyes
 Anatomically consistent landmark in all human eyes

BMO is a true anatomic boundary of the RGC axons

BMOcentroid is the center of BMO

Fovea is the anatomic center of the retina

RGC axons organized relative to the FoBMO axis
From: D. Hood et al., Glaucomatous Damage in the Macula,
Prog Retin Eye Res 2013; 1-21.
Anatomic Positioning System - APS
BMO
Fovea
Anatomic Positioning System - APS

Locates points in the eye using two fixed, structural landmarks
 center of the fovea and
 center of the Bruch’s Membrane Opening (BMO)

Automatic detection of landmarks during initial APS scan
 Automatic alignment of scans relative to patient’s individual
Fovea to - Bruch’s Membrane Opening (FoBMO) center axis
 Consistent, accurate placement of subsequent scans and
sectors for data analysis
 Automatic adjustment for head tilt during acquisition
Anatomic Positioning System - APS
Without SPECTRALIS APS
 Same eye scanned
on separate visits
(no APS or AutoRescan)
 Head tilt causes significant variability of classification results
Anatomic Positioning System - APS
With SPECTRALIS APS
 Consistent positioning for
each individual’s anatomy
 Two eyes with different
anatomical positions of
fovea relative to the center
of the BMO (A and B)
 Scan orientation automatically aligned along the individual’s
FoBMO axis
Anatomic Positioning System - APS
 Accurate geometric relations between nerve fiber defects can be established,
which are observed in ONH, RNFL and the Posterior Pole Asymmetry Analysis
 Easy correlation between analysis methods
Anatomic Positioning System - APS
Advantages
 Automatic
 Consistent
 Individual / Customized
 Reliable
SPECTRALIS Glaucoma Module Premium Edition
BMO Rim Analysis
SPECTRALIS Glaucoma Module Premium Edition
Current Sectors
Garway-Heath Sectors
Advantages
90°
110°
 Sector orientation aligned
with nerve fiber bundle
trajectory
 Better structure-function
correlation
 Same eye – different sector distribution
References:
Garway-Heath DF et al. Mapping the Visual Field to the Optic Disc
in Normal Tension Glaucoma Eyes.
Ophthalmology 2000; 107: 1809–1815.
SPECTRALIS Glaucoma Module Premium Edition
Current Classification
New Display
Percentile:
 Percentage of normal eyes
have a rim this thin or thinner
Actual thickness
(Mean thickness value)
Actual thickness
(Percentile)
 Different eyes – different displays
 Remember HRT !!!
SPECTRALIS Glaucoma Module Premium Edition
Internally
oblique at
nasal side
Externally
oblique at
temp. side
Within normal limits
Borderline
Outside normal limits
BMO Overview
SPECTRALIS Glaucoma Module Premium Edition
Progression
SPECTRALIS Glaucoma Module Premium Edition
BMO Size: 1.85 mm2
BMO Size: 1.85 mm2
BMO-MRW OU Report
SPECTRALIS Glaucoma Module Premium Edition
BMO-MRW & RNFL Single Eye Report

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