Retinal Nerve Fiber Layer Thickness by GDx

7/25/2014
Optic nerve head evaluation
The goal of this evaluation is to differentiate
between normal and glaucomatous eyes and to
detect progression of glaucomatous damage.
A PILOT STUDY TO ESTIMATE THE CORRELATION
BETWEEN DISC DAMAGE LIKELIHOOD SCALE
AND RETINAL NERVE FIBRE LAYER THICKNESS
BY GDx
GDx--VCC SCANNING LASER POLARIMETRY IN
GLAUCOMA
The best method readily available to the clinician
is high plus lens fundus biomicroscopy.
biomicroscopy.
Various systems for staging the glaucomatous
nerve damage are based on enlargement of cup
like Armaly’s method
Author : Dr.Prashanth.R
Co--Authors: Dr.Sharmila.R,
Co
Dr.Sharmila.R, Dr.Nalini.D,
Dr.Nalini.D,
Dr.Krishnadas.S.R
Aravind Eye Hospital
Madurai
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Armaly’s nomogram
It does not describe directly the actual change
occurring in glaucoma, namely, the loss of
neuroretinal rim tissue.
0.3 CDR
Neuroretinal rim area outperforms the C/D ratio in its
correlation with visual function
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Disc
Damage Likelihood Scale

Rim
thinning
New disc grading system
stages glaucomatous optic nerve damage
based upon the narrowest radial width of
rim
The cup/disk ratio does not
correct for the effect of optic
nerve size
The cup/disk ratio system does
not possess high interobserver
reliability as compared to
DDLS*..
DDLS*
*Lichter P. Variabilty of expert observers in evaluating the optic disc. Trans Am ophthalmol Soc 1976; 74:532-572
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Our study…
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9 Inclusion criteria
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Aim:
To determine the correlation of a new disc
grading system, the DDLS and retinal
nerve layer thickness by scanning laser
polarimetry (SLP) in eyes with clinically
established glaucoma.
To study the correlation of DDLS with
functional alteration in glaucoma
determined by automated perimetry
9
9
Age > 18 years
reliable automated perimetry
best--corrected visual acuity ≥ 6/12
best
9Exclusion criteria
9Myopia > 5 dioptres
9Any corneal, retinal, optic nerve (except glaucoma) or
neurologic pathology associated with visual field defects
9Optic disk abnormalities (tilted optic disc, optic disc drusen,
drusen,
optic disc pit, optic disc coloboma)
coloboma)
9Macular pathology and vitreous opacities
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Methodology
Methodology
Examinations - Visual acuity, intra ocular
pressure, central corneal thickness, slit
lamp biomicroscopy
biomicroscopy,, Gonioscopy
DDLS staging
g g by
y an ophthalmologist
p
g
RNFL analysis using GDx
GDx--VCC,
HFA (24(24-2 program)
Observational case series
worse eye of patients with clinically
established glaucoma
conducted
d t d ffrom July
J l 2008 till JJuly
l 2009
100 eyes of 100 patients with known
glaucoma attending glaucoma clinic.
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10
Steps
Statistical Analysis
DDLS was compared to the parameters of
GDx and Mean deviation of visual fields
using Pearson’s correlation coefficient
Dilate pupils
Size of optic disc

Paired tt--test/ANOVA was used to compare
the means.
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60D – x1.0; 78D – x1.1;
90D – x1.3
Small <1.5mm; avg 1.5 –
2mm; large >2mm
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Note the area where rim is narrowest
Calculate rim
rim--disc ratio
DDLS Stage according to nomogram
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Quantification
Results
Characteristics of study population
Stages 1 - 4 : no definite damage
Stages 5 – 7 : asymptomatic damage
Stages 8 – 10 : disability
Age (Yrs) [ mean ± SD ]
55.55 ± 13.12
Sex
Male / Female
70/ 30
Eye
Right/Left
g
64/ 36
IOP [ mm Hg ]
(mean ± SD)
18.46 ± 6.27
Type of Glaucoma
15
Primary open angle
82
Pseudoexfoliation
08
Chronic angle closure
10
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Results
Results
DDLS stage (mean ±
SD)
GDX – VCC
Parameters (mean ±
SD)
Visual field indices
(mean ± SD)
6.41 ± 1.62
NFI
56.81 ± 26.35
Mean Deviation
-15.08 ± 8.88
g
TSNIT Average
41.28 ± 10.29
PSD
8.37 ± 4.02
No.off Subjects
67
70
60
50
40
30
20
10
0
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4
Small
Average
Superior Average
46.26 ± 14.12
Large
Fundus Disc Diameter
Inferior Average
44.685 ± 11.41553
2/3rd of patients were having average size disc
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Correlation between Fundus DDLS
and TSNIT AVG
2
2
4
4
Fun
ndus DDLs
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ndus DDLs
Fun
6
8
8
10
10
Correlation between Fundus DDLS
and GDx_NFI
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0
20
40
GDx NFI
Observed
60
80
100
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Fitted
30
40
50
GDx TSNIT AVERAGE
Observed
There is a significance positive correlation(r=0.5223,p-value <0.01)
between DDLs and NFI
60
70
Fitted
There is a significance Negative correlation(r=-0.4227, p-value<0.01)
between DDLs and TSNIT avg
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DDLS status with NFI and Mean
deviation
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correlation between DDLS and
Visual fields mean deviation
2
4
Fun
ndus DDLs
6
8
DDLS
-40
-30
-20
Visual Fields Mean Deviation
Observed
-10
NFI
Mean deviation
1-4
40.00±20.49
5-7
51.86±23.42
-9.50±8.44
-13.78±7.86
8-10
77.45±24.88
-21.36±9.42
P-Value
<0.001
0.0003
0
Fitted
There is a significance Negative correlation(r=-0.4545, p-value<0.01)
between DDLs and Visual fields mean deviation
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DISCUSSION
RESULTS
Correlation of DDLS stage
GDx--VCC’s NFI ( Nerve
GDx
fibre indicator )
r = 0.52, p < 0.01
Small sized discs
r=0.60, p-value<0.01
Average sized discs
r=0.52, p-value<0.01
Large sized discs
r=-0.4093, p-value=0.5907
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Optic disc morphology has been shown to
be correlated with the visual field indices
and nerve fiber layer thickness by many
authors
In our study, the DDLS is highly correlated
with the GDX
GDX--VCC parameters and visual
field indices
Correlation was also significant in three
diagnostic groups (POAG, PXFG, CACG)
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DISCUSSION
Advantages
In our patients, correlation was significant
in small (1.5 mm) and average size (1.5–
(1.5–
2.0 mm) disks. However, it was not so
good in large (2.0 mm) disks.
This is probably an expression of the
fewer number of subjects (n = 4) having
large disks.
High inter & intraintra-observer reproducibility
Greater correlation with visual field
changes
Measures
M
th
the rim
i width
idth
Considers disc size
Quantification of damage
1
2,3
Validity of new disc grading scale for estimating glaucomatous damage :
correlation with visual field damage. Am J ophthalmol 2002;133:758-763
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Limitations of DDLS
1.Reliability of DDLS. Am J ophthalmol 2003; 135:44-48
2.Validity of new disc grading scale for estimating glaucomatous damage : correlation with
visual field damage. Am J ophthalmol 2002;133:758-763
3.Regional correlation of structure and function in glaucoma, using the DDLS, HRT and visual
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fields. Ophthalmology 2006;113:603-611
Conclusion
Location of rim narrowing is not
considered
Non--contiguous areas of lesser damage is
Non
not considered
Congenital disc anomalies or other
atypical discs don’t fit into any scale
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DDLS, a new disc scoring system takes into
account both the rim loss and disc size.
Our study demonstrated a strong correlation
between DDLS and GDxGDx-VCC for small and
average sized discs and it also gave information
regarding the stage of the disease.
However still larger studies are required for
validation
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