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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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Related in: MedlinePlus

The results of the region of interest (ROI) separation in the polar coordinate presented in Cartesian coordinate system. The present region of interest is the basis for further analysis related to the determination of the features associated with the area change in the RNFL thickness and the percentage of the area cup/disk ratio. These features are the basis for determining their correlation with the results of perimetry. The areas TE, SU, NA, IN denoting the following areas respectively: temporal, superior, nasal, inferior have been marked on the axis θ. The cup boundaries are marked in red and disk boundaries in green.
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Figure 7: The results of the region of interest (ROI) separation in the polar coordinate presented in Cartesian coordinate system. The present region of interest is the basis for further analysis related to the determination of the features associated with the area change in the RNFL thickness and the percentage of the area cup/disk ratio. These features are the basis for determining their correlation with the results of perimetry. The areas TE, SU, NA, IN denoting the following areas respectively: temporal, superior, nasal, inferior have been marked on the axis θ. The cup boundaries are marked in red and disk boundaries in green.

Mentions: The function atan2 returns θ the same size as n and i containing the element-by-element, four-quadrant inverse tangent (arctangent) of the real parts of n and i. The obtained results, the ROI in the polar coordinate system LRNFL*(θ,ρ), are shown in Figure 7. The proposed algorithm is shown globally in a block diagram form in Figure 8. On the basis of the presented ROI, the following results (features) were obtained: the disk diameter and its relation to the cup and RNFL parameters. Their thorough analysis and correlation with the results from perimetry are presented in the next section.


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 results of the region of interest (ROI) separation in the polar coordinate presented in Cartesian coordinate system. The present region of interest is the basis for further analysis related to the determination of the features associated with the area change in the RNFL thickness and the percentage of the area cup/disk ratio. These features are the basis for determining their correlation with the results of perimetry. The areas TE, SU, NA, IN denoting the following areas respectively: temporal, superior, nasal, inferior have been marked on the axis θ. The cup boundaries are marked in red and disk boundaries in green.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 7: The results of the region of interest (ROI) separation in the polar coordinate presented in Cartesian coordinate system. The present region of interest is the basis for further analysis related to the determination of the features associated with the area change in the RNFL thickness and the percentage of the area cup/disk ratio. These features are the basis for determining their correlation with the results of perimetry. The areas TE, SU, NA, IN denoting the following areas respectively: temporal, superior, nasal, inferior have been marked on the axis θ. The cup boundaries are marked in red and disk boundaries in green.
Mentions: The function atan2 returns θ the same size as n and i containing the element-by-element, four-quadrant inverse tangent (arctangent) of the real parts of n and i. The obtained results, the ROI in the polar coordinate system LRNFL*(θ,ρ), are shown in Figure 7. The proposed algorithm is shown globally in a block diagram form in Figure 8. On the basis of the presented ROI, the following results (features) were obtained: the disk diameter and its relation to the cup and RNFL parameters. Their thorough analysis and correlation with the results from perimetry are presented in the next section.

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