1. SPECTRALIS® Glaucoma Module Premium Edition

2. Clinical Mismatch
Mismatch between clinically visible disc margin & SD-OCT-based disc margin
SD-OCT BMO
Obvious mismatch between clinician´s opinion and the SD-OCT-based disc margin. Where is the clinician looking for? Brightness changes (reflectivity), scleral ring (pale band), bending vessels, symmetry considerations.
How does the SD-OCT define the disc margin? Are there anatomical landmarks the instrument is using as referring points? > Bruch´s Membrane Opening (BMO)
Clinically Visible Optic Disc Margin
Image Courtesy Dr. Balwantray C. Chauhan, Halifax, Canada and Dr. Claude F. Burgoyne, Portland, USA.

3. Variable Rim Tissue Internally oblique Non-oblique Externally oblique
Image Courtesy Dr. B.C. Chauhan, Halifax, Canada.
Clinical disc margin
BMO
Reis et al. Ophthalmology 119: ,2012.

4. 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
Clinician sees BMO (1), some aspect of border tissue of Elschnig (2) or indetermined structures of border tissue or Elschnig(3).
Most predominant structure recognized as DM is some aspect of border tissue.
BMO mostly invisible for clinician and by photography. Only SD-OCT able to detect deeper, relevant anatomical landmarks. Current disc margin delineation often inconsistent, inter-individually not always reproducible.

5. Overestimation of Rim Tissue
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. DM
BMO
Image Courtesy Dr. B.C. Chauhan, Halifax, Canada.
An overestimation of rim tissue means the patient appears to be healthier than he/she actually is. The image to the right shows a significant mismatch of the clinical DM and the SD-OCT based DM. Clinical DM underestimates the remaining rim; whereas SD-OCT based disc margin is far outside.

6. Invisible BMO
Bruch's Membrane Opening is a consistent landmark, but it is usually clinically and photographically invisible.
BMO
ONLY SD-OCT makes the BMO visible.
No more vague interpretations of disc margin
operator-independent
reproducible
Image Courtesy Dr. B.C. Chauhan, Halifax, Canada.

7. 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.
Reis et al. Invest Ophthalmology Vis Sci. 53: , 2012.
BMO-MRW

8. Correct Rim Measurement
Reis et al. Invest Ophthalmology Vis Sci. 53: , 2012.
BMO-MRW
Neuroretinal rim measurement from 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 varying trajectory at all 48 points of measurement
Basic Information
Cross Section of RNF

9. 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)

10. 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

11. 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
Geometric perspectives:
The justification of choosing FoBMO axis is based on the anatomy.
Both fovea and BMO centroid are anatomically consistent landmarks in human eyes.
D. Hood and colleagues: retinal ganglion cell axons organized in a way along the FoBMO axis
Figure 15.
Changes in the RNFL bundle projections with different locations of the optic disc. (A) A digitally red-filtered fundus photo with tracings of 3 RNFL bundles in red. (B) Tracings as in panel A for 11 eyes. The green square with the red dot is the center of the optic disc. The open green square is the location on the disc associated with the RNFL originating at the 3 o'clock position on the red circles around the fovea. (C) Tracings from panel B after scaling and rotating to align the centers of the optic discs.
From: D. Hood et al., Glaucomatous Damage in the Macula, Prog Retin Eye Res 2013; 1-21.

12. Anatomic Positioning System - APS
BMO
Fovea
FoBMO - Axis

13. 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
Key Feature !!!

14. 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

15. 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

16. 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
Unique to SPECTRALIS !!!

17. Anatomic Positioning System - APS
Advantages
Automatic
Individual / Customized
Consistent
Reliable
No other OCT offers this functionality !!!

18. SPECTRALIS Glaucoma Module Premium Edition
Rim analysis: IR image + SD-OCT B-scan
Classification into WNL, Borderline and ONL
BMO Rim Analysis

19. SPECTRALIS Glaucoma Module Premium Edition
Garway-Heath Sectors
40°
110°
90°
Same eye – different sector distribution
Current Sectors
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

20. SPECTRALIS Glaucoma Module Premium Edition
New Display
Different eyes – different displays
Actual thickness
(Percentile)
Current Classification
Percentile:
Percentage of normal eyes have a rim this thin or thinner
Actual thickness
(Mean thickness value)
Remember HRT !!!

21. SPECTRALIS Glaucoma Module Premium Edition
Internally oblique at
nasal side
Externally oblique at
temp. side
BMO Overview gives information on the overall status of the ONH. Color of arrows (BMO-MRW) dependent on classification of corresponding sector.
Corresponding fundus camera image can be loaded and displayed in center instead of IR image showing disc margin based on SD-OCT image.
Within normal limits
Borderline
Outside normal limits
BMO Overview

22. SPECTRALIS Glaucoma Module Premium Edition
„Beyond one´s own nose“
Progression

23. SPECTRALIS Glaucoma Module Premium Edition
BMO Size: 1.85 mm2
BMO Size: 1.85 mm2
BMO-MRW OU Report

24. SPECTRALIS Glaucoma Module Premium Edition
BMO-MRW & RNFL Single Eye Report