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Automatic method of analysis of OCT images in assessing the severity degree of glaucoma and the visual field loss.

Koprowski R, Rzendkowski M, Wróbel Z - Biomed Eng Online (2014)

Bottom Line: The obtained results were compared with the results obtained from a static perimeter.Correlations between the known parameters of the optic disk as well as those suggested by the authors and the results obtained from static perimetry were calculated.The following results of correlation for the three proposed classes were obtained: cup/disk diameter 0.84, disk diameter 0.97 and the RNFL 1.0.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Biomedical Computer Systems, Faculty of Computer Science and Materials Science, Institute of Computer Science, University of Silesia, ul, Będzińska 39, Sosnowiec 41-200, Poland. robert.koprowski@us.edu.pl.

ABSTRACT

Introduction: In many practical aspects of ophthalmology, it is necessary to assess the severity degree of glaucoma in cases where, for various reasons, it is impossible to perform a visual field test - static perimetry. These are cases in which the visual field test result is not reliable, e.g. advanced AMD (Age-related Macular Degeneration). In these cases, there is a need to determine the severity of glaucoma, mainly on the basis of optic nerve head (ONH) and retinal nerve fibre layer (RNFL) structure. OCT is one of the diagnostic methods capable of analysing changes in both, ONH and RNFL in glaucoma.

Material and method: OCT images of the eye fundus of 55 patients (110 eyes) were obtained from the SOCT Copernicus (Optopol Tech. SA, Zawiercie, Poland). The authors proposed a new method for automatic determination of the RNFL (retinal nerve fibre layer) and other parameters using: mathematical morphology and profiled segmentation based on morphometric information of the eye fundus. A quantitative ratio of the quality of the optic disk and RNFL - BGA (biomorphological glaucoma advancement) was also proposed. The obtained results were compared with the results obtained from a static perimeter.

Results: Correlations between the known parameters of the optic disk as well as those suggested by the authors and the results obtained from static perimetry were calculated. The result of correlation with the static perimetry was 0.78 for the existing methods of image analysis and 0.86 for the proposed method. Practical usefulness of the proposed ratio BGA and the impact of the three most important features on the result were assessed. The following results of correlation for the three proposed classes were obtained: cup/disk diameter 0.84, disk diameter 0.97 and the RNFL 1.0. Thus, analysis of the supposed visual field result in the case of glaucoma is possible based only on OCT images of the eye fundus.

Conclusions: The calculations and analyses performed with the proposed algorithm and BGA ratio confirm that it is possible to calculate supposed mean defect (MD) of the visual field test based on OCT images of the eye fundus.

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The result for one patient obtained from the Copernicus tomograph. The following images can be seen in the corners: fundus reconstruction, a deviation from the normal map, the RNFL thickness map and the graph RNFL TSNIT. In the central part at the bottom there is a sample B-scan of the optic disk. The central part is dedicated to the ratios calculated by the software.
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Figure 2: The result for one patient obtained from the Copernicus tomograph. The following images can be seen in the corners: fundus reconstruction, a deviation from the normal map, the RNFL thickness map and the graph RNFL TSNIT. In the central part at the bottom there is a sample B-scan of the optic disk. The central part is dedicated to the ratios calculated by the software.

Mentions: As stated in the previous section, a visual field test was performed on 55 glaucoma patients. The features of the eye fundus were measured using a Copernicus tomograph. The results obtained in the software available for these devices are shown in Figure 2 and Figure 3. The features obtained on this basis are presented in Table 1. Examples of values for each feature for the first 10 patients are shown in Table 2. Each of these characteristics will be further, for simplicity, denoted by the symbol “w”. In this case, the features from w(1) to w(28) were acquired from the tomograph, and w(29) and w(30) from the perimeter. The parameters from w(1) to w(30) were further subjected to exploratory factor analysis in order to detect their cross correlation and to remove those features which are statistically insignificant. For this purpose, the following items were designated in succession: correlation of features w, eigenvalues of the correlation matrix, the number of classes using the Kaiser’s and Cattell’s criteria, rotation of the coordinate system, correlation of individual features with the newly created classes. The results (for the whole group of patients) are shown in Table 3 whereas the correlation chart of various features with three classes are shown in Figure 4. The analysis of Table 3 and Figure 4 suggests several conclusions useful for further analysis:


Automatic method of analysis of OCT images in assessing the severity degree of glaucoma and the visual field loss.

Koprowski R, Rzendkowski M, Wróbel Z - Biomed Eng Online (2014)

The result for one patient obtained from the Copernicus tomograph. The following images can be seen in the corners: fundus reconstruction, a deviation from the normal map, the RNFL thickness map and the graph RNFL TSNIT. In the central part at the bottom there is a sample B-scan of the optic disk. The central part is dedicated to the ratios calculated by the software.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC3928579&req=5

Figure 2: The result for one patient obtained from the Copernicus tomograph. The following images can be seen in the corners: fundus reconstruction, a deviation from the normal map, the RNFL thickness map and the graph RNFL TSNIT. In the central part at the bottom there is a sample B-scan of the optic disk. The central part is dedicated to the ratios calculated by the software.
Mentions: As stated in the previous section, a visual field test was performed on 55 glaucoma patients. The features of the eye fundus were measured using a Copernicus tomograph. The results obtained in the software available for these devices are shown in Figure 2 and Figure 3. The features obtained on this basis are presented in Table 1. Examples of values for each feature for the first 10 patients are shown in Table 2. Each of these characteristics will be further, for simplicity, denoted by the symbol “w”. In this case, the features from w(1) to w(28) were acquired from the tomograph, and w(29) and w(30) from the perimeter. The parameters from w(1) to w(30) were further subjected to exploratory factor analysis in order to detect their cross correlation and to remove those features which are statistically insignificant. For this purpose, the following items were designated in succession: correlation of features w, eigenvalues of the correlation matrix, the number of classes using the Kaiser’s and Cattell’s criteria, rotation of the coordinate system, correlation of individual features with the newly created classes. The results (for the whole group of patients) are shown in Table 3 whereas the correlation chart of various features with three classes are shown in Figure 4. The analysis of Table 3 and Figure 4 suggests several conclusions useful for further analysis:

Bottom Line: The obtained results were compared with the results obtained from a static perimeter.Correlations between the known parameters of the optic disk as well as those suggested by the authors and the results obtained from static perimetry were calculated.The following results of correlation for the three proposed classes were obtained: cup/disk diameter 0.84, disk diameter 0.97 and the RNFL 1.0.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Biomedical Computer Systems, Faculty of Computer Science and Materials Science, Institute of Computer Science, University of Silesia, ul, Będzińska 39, Sosnowiec 41-200, Poland. robert.koprowski@us.edu.pl.

ABSTRACT

Introduction: In many practical aspects of ophthalmology, it is necessary to assess the severity degree of glaucoma in cases where, for various reasons, it is impossible to perform a visual field test - static perimetry. These are cases in which the visual field test result is not reliable, e.g. advanced AMD (Age-related Macular Degeneration). In these cases, there is a need to determine the severity of glaucoma, mainly on the basis of optic nerve head (ONH) and retinal nerve fibre layer (RNFL) structure. OCT is one of the diagnostic methods capable of analysing changes in both, ONH and RNFL in glaucoma.

Material and method: OCT images of the eye fundus of 55 patients (110 eyes) were obtained from the SOCT Copernicus (Optopol Tech. SA, Zawiercie, Poland). The authors proposed a new method for automatic determination of the RNFL (retinal nerve fibre layer) and other parameters using: mathematical morphology and profiled segmentation based on morphometric information of the eye fundus. A quantitative ratio of the quality of the optic disk and RNFL - BGA (biomorphological glaucoma advancement) was also proposed. The obtained results were compared with the results obtained from a static perimeter.

Results: Correlations between the known parameters of the optic disk as well as those suggested by the authors and the results obtained from static perimetry were calculated. The result of correlation with the static perimetry was 0.78 for the existing methods of image analysis and 0.86 for the proposed method. Practical usefulness of the proposed ratio BGA and the impact of the three most important features on the result were assessed. The following results of correlation for the three proposed classes were obtained: cup/disk diameter 0.84, disk diameter 0.97 and the RNFL 1.0. Thus, analysis of the supposed visual field result in the case of glaucoma is possible based only on OCT images of the eye fundus.

Conclusions: The calculations and analyses performed with the proposed algorithm and BGA ratio confirm that it is possible to calculate supposed mean defect (MD) of the visual field test based on OCT images of the eye fundus.

Show MeSH
Related in: MedlinePlus