176
E. Gao et al.
From the conclusion above, it is necessary to normalize the intensity with signal
strength. Various methods have been used in the literature [10, 12, 16] and different
layer intensities have been used as reference. This study found that in normal subjects,
the optical intensity in GCL, IPL, INL, OPL and ONL were highly correlated with
each other and image quality, their r
2 with image quality is more than 80%. Based
on these results, we recommend GCL, IPL, INL, OPL or ONL as references for
normalization. In addition, as the image quality index and the optical intensity of all
areas both had good correlation with optical intensities of intraretinal layers, they
can also be the reference for normalization.
A week negative correlation was found between RNFL with age (r −0.365, p
0.021), even after adjust of image quality, which did not apply to other layers. It is a
new finding. It is well recognized that the RNFL thickness was reduced in glaucoma
patients [28] and aged subjects [29]. The optical intensity of RNFL was also reported
lower in patients with glaucoma compared to control or ocular hypertension [8, 14].
Hence, further investigations are desired to clarify the role RNFL optical intensity
in diagnosis of glaucoma.
7.4 Distribution and Determinants of the Optical Intensity
of Retinal Layers of Normal Subjects
The automatic segmentation approach was also used to determine the distribution of
optical intensity of each layer and regions specified by the Early Treatment of Diabetic
Retinopathy Study (ETDRS) in 231 eyes from 231 healthy subjects ranging in age
from 18 to 80 years old [26]. Forty-four eyes were randomly chosen to be scanned by
two operators for reproducibility analysis. Univariate and multivariate analysis were
performed between retinal optical intensity and sex, age, height, weight, spherical
equivalent (SE), axial length, image quality, disc area and rim/disc area ratio (R/D
area ratio).
7.4.1 Data Acquisition and Image Processing
All subjects received scans by experienced operators with Topcon 3D OCT-2000
(Topcon, Tokyo, Japan, software version: 8.11.003.04) without pupil dilatation.
Three-dimensional image data were acquired using the scan mode of 3D macular (512 × 128) centered at the fovea and covering a 6 × 6 mm
2 area. Scanning was
performed with the measurement beam perpendicular to the retina (light entered the
eyes across the central position of the pupil). Forty-four eyes were randomly chosen
to be scanned by the two operators on the same day for reproducibility analysis.
The axial resolution was 5–6 μm and transverse resolution was 20 μm. Images, of
a quality of 45 or higher, were included. Parameters, such as disc area and rim/disc
E. Gao et al.
From the conclusion above, it is necessary to normalize the intensity with signal
strength. Various methods have been used in the literature [10, 12, 16] and different
layer intensities have been used as reference. This study found that in normal subjects,
the optical intensity in GCL, IPL, INL, OPL and ONL were highly correlated with
each other and image quality, their r
2 with image quality is more than 80%. Based
on these results, we recommend GCL, IPL, INL, OPL or ONL as references for
normalization. In addition, as the image quality index and the optical intensity of all
areas both had good correlation with optical intensities of intraretinal layers, they
can also be the reference for normalization.
A week negative correlation was found between RNFL with age (r −0.365, p
0.021), even after adjust of image quality, which did not apply to other layers. It is a
new finding. It is well recognized that the RNFL thickness was reduced in glaucoma
patients [28] and aged subjects [29]. The optical intensity of RNFL was also reported
lower in patients with glaucoma compared to control or ocular hypertension [8, 14].
Hence, further investigations are desired to clarify the role RNFL optical intensity
in diagnosis of glaucoma.
7.4 Distribution and Determinants of the Optical Intensity
of Retinal Layers of Normal Subjects
The automatic segmentation approach was also used to determine the distribution of
optical intensity of each layer and regions specified by the Early Treatment of Diabetic
Retinopathy Study (ETDRS) in 231 eyes from 231 healthy subjects ranging in age
from 18 to 80 years old [26]. Forty-four eyes were randomly chosen to be scanned by
two operators for reproducibility analysis. Univariate and multivariate analysis were
performed between retinal optical intensity and sex, age, height, weight, spherical
equivalent (SE), axial length, image quality, disc area and rim/disc area ratio (R/D
area ratio).
7.4.1 Data Acquisition and Image Processing
All subjects received scans by experienced operators with Topcon 3D OCT-2000
(Topcon, Tokyo, Japan, software version: 8.11.003.04) without pupil dilatation.
Three-dimensional image data were acquired using the scan mode of 3D macular (512 × 128) centered at the fovea and covering a 6 × 6 mm
2 area. Scanning was
performed with the measurement beam perpendicular to the retina (light entered the
eyes across the central position of the pupil). Forty-four eyes were randomly chosen
to be scanned by the two operators on the same day for reproducibility analysis.
The axial resolution was 5–6 μm and transverse resolution was 20 μm. Images, of
a quality of 45 or higher, were included. Parameters, such as disc area and rim/disc