I.
Structural Assessment in Glaucoma
A. 1st Global Consensus Meeting on “Structure and Function in the Management of
Glaucoma”. AIGS, November 2003.
“New imaging techniques give a similar diagnostic performance as a Fellowship trained
glaucoma specialist”
II.
Assessent of the Optic Nerve Head
A. Ophthalmoscopy
B. Fundus Biomicroscopy – Super 66
C. Stereoscopic Photography
D. Three Dimensional Imaging of the Optic Nerve and Retina
III.
Scanning Laser Tomography – The New Clinical Standard?
A. Heidelberg Retina Tomograph (HRT)
B. How does it work?
1. Confocal optics, multiple images in depth
2. Analogous to CT scan
3. HRTII: 15x15 degree image; 384x384 pixels; 680nm diode laser;
automated scan depth, sensitivity setting and focus quality control; 3 image
series per acquisition.
4. Accuracy, validity and reproducibility.
C. Clinical application.
1. 3-D
2. Judging image quality
3. Drawing the contour
4. Understanding the printout
a) Topography image
b) Reflectance image
c) Mean height contour line
d) Horizontal and Vertical Height Profiles
5. Stereometric parameters
a) Five most important:
(1) Rim Volume
(2) Rim Area
(3) Cup Shape
(4) Height Variation Contour
(5) Mean RNFL Thickness
b) Multivariate Analysis
D. Analysis of ONH Topography
1. Classification:
a) Parameters differ between diagnostic groups
b) But physiological variability high
2. Moderate sensitivity and specificity
3. Studies
a) Burk et al, Graefe’s Arch Clin Exp Ophthalmol, 1993
b) Uchida et al, Invest Ophthalmol Vis Sci, 1996
c) Hatch et al, Br J Ophthalmol, 1997
d) Mikelberg et al, J Glaucoma, 1998
e) Bathija et al, J Glaucoma, 1998
f) Wollstein et al, Ophthalmology, 1998
g) Bartz-Schmidt et al, Surv Ophthalmol, 1999
4. Discriminative Ability
a) Zangwill et al, Arch Ophthalmol, 2001
b) Greaney et al, Invest Ophthalmol Vis Sci, 2002
5. Moorfields Regression Analysis
E. Analysis of Progression
1. Parametric description
2.
Topographic difference maps
3.
Change probability maps
a) Chauhan et al., IOVS 2000;41:775-782
b) Red illustrates progression
c) Capable of detecting progression prior to visual fields?
F. Topographic Change
1.
Diagnosis
2.
Progression
a)
IV.
Studies
(1)
(2)
(3)
(4)
Kamal et al, Br J Ophthalmol, 1999
Chauhan et al, Arch Ophthalmol, 2001
Burgoyne et al, Ophthalmology, 2002
Ervin et al, Ophthalmology, 2002
(a) Performance at least equal to fellowship trained
glaucoma specialists for the detection of ONH surface
change
IMAGING OF THE NERVE FIBRE LAYER
A. Optical Coherence Tomography (OCTIII)
1. How does it work?
a) Low-coherence interferometry
b) 512 individual axial scans, combined to give scan series
c) Each scan analogous to A-scan ultrasound
2. Accuracy, validity and reproducibility.
3. Clinical application.
B. Scanning Laser Polarimetry (GDx)
1. How does it work?
2. Birefringence and Retardation
a) Nerve fiber layer is form-birefringent
b) Light passing through a birefringent medium undergoes a phase
shift, “slows down" (retardation)
c) Detector measures retardation between phase shifted ray and
unshifted ray
d) Amount of retardation is directly proportional to the thickness of
the nerve fiber layer
3. Accuracy, validity and reproducibility.
4. Clinical application.
a) Custom Corneal Compensation
b) Deviation Plot