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SPECTRALIS® Glaucoma Module Premium Edition. Clinical Mismatch. Mismatch between clinically visible disc margin & SD-OCT-based disc margin. SD-OCT BMO. Clinically Visible Optic Disc Margin. - PowerPoint PPT Presentation
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SPECTRALIS® Glaucoma Module Premium Edition
SD-OCT BMO
Clinically Visible Optic Disc Margin
Image Courtesy Dr. Balwantray C. Chauhan, Halifax, Canada and Dr. Claude F. Burgoyne, Portland, USA.
Clinical Mismatch
Mismatch between clinically
visible disc margin &
SD-OCT-based disc margin
Variable Rim Tissue Internally oblique
Non-oblique
Reis et al. Ophthalmology 119:738-747,2012.
Externally oblique
Image Courtesy Dr. B.C. Chauhan, Halifax, Canada.
Clinical disc margin
BMO
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
Clinical Disc Margin
Consequences
Inconsistent definition of the
disc margin can mean an
underestimation of rim tissue.
Using Bruch´s membrane opening (BMO)
as a stable landmark provides a more
accurate measurement of the ONH rim tissue.
DMBMO
Image Courtesy Dr. B.C. Chauhan, Halifax, Canada.
Overestimation of Rim Tissue
Invisible BMO
Bruch's Membrane Opening is a consistent landmark,
but it is usually clinically and photographically invisible.
Image Courtesy Dr. B.C. Chauhan, Halifax, Canada.
BMO
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.
Geometric Orientation
Reis et al. Invest Ophthalmology Vis Sci. 53: 1852-1860, 2012.
BMO-MRW
Correct Rim Measurement
Bas
ic In
form
atio
n
Neuroretinal rim measurementfrom BMO to nearest point on internal limiting membrane (ILM)
Shortest distance measurement
Quantification of perpendicular cross section of nerve fibers exiting the eye
Taking into account their varyingtrajectory at all 48 points of measurement
Reis et al. Invest Ophthalmology Vis Sci. 53: 1852-1860, 2012.
BMO-MRW
Cross Section of RNF
Current Reality
Current sectorial analysis
is made with fixed horizontal
and vertical axes on the image.
AIF Vertical (S/I) Axis
Acquired Image Frame (AIF)
AIF Horizontal (N/T) Axis
Inter-individual variability in the axis connecting the
Fovea and Bruch’s Membrane Opening (BMO) center
Range of Variability of FoBMO Axes
+ 2° to
- 18° *<* Examples taken from the HDEng SPECTRALIS normative data collection
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.
Anatomically Normalized Eyes
Anatomic Positioning System - APS
Fovea
BMO
FoBMO - Axis
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
Individual / Customized
Consistent
Reliable
BMO Rim Analysis
SPECTRALIS Glaucoma Module Premium Edition
SPECTRALIS Glaucoma Module Premium Edition
Current Sectors Garway-Heath Sectors
40°
110°90°
40°40°
40°
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.
Advantages
Sector orientation aligned
with nerve fiber bundle
trajectory
Better structure-function
correlation
SPECTRALIS Glaucoma Module Premium Edition
Current Classification
Percentile: Percentage of normal eyes
have a rim this thin or thinner
Actual thickness(Mean thickness value)
New Display
Different eyes – different displays
Actual thickness(Percentile)
Remember HRT !!!
BMO Overview
Within normal limits
Borderline
Outside normal limits
Internally oblique at nasal side
Externally oblique at temp. side
SPECTRALIS Glaucoma Module Premium Edition
SPECTRALIS Glaucoma Module Premium Edition
Progression
SPECTRALIS Glaucoma Module Premium Edition
BMO-MRW OU Report
BMO Size: 1.85 mm2 BMO Size: 1.85 mm2
SPECTRALIS Glaucoma Module Premium EditionSPECTRALIS Glaucoma Module Premium Edition
BMO-MRW & RNFL Single Eye Report