Abstract
PURPOSE: To develop a fully automated algorithm (AP) to perform a volumetric measure of the optic disc using conventional stereoscopic optic nerve head (ONH) photographs, and to compare algorithm-produced parameters with manual photogrammetry (MP), scanning laser ophthalmoscope (SLO) and optical coherence tomography (OCT) measurements. METHODS: One hundred twenty-two stereoscopic optic disc photographs (61 subjects) were analyzed. Disc area, rim area, cup area, cup/disc area ratio, vertical cup/disc ratio, rim volume and cup volume were automatically computed by the algorithm. Latent variable measurement error models were used to assess measurement reproducibility for the four techniques. RESULTS: AP had better reproducibility for disc area and cup volume and worse reproducibility for cup/disc area ratio and vertical cup/disc ratio, when the measurements were compared to the MP, SLO and OCT methods. CONCLUSION: AP provides a useful technique for an objective quantitative assessment of 3D ONH structures.
Highlights
Glaucoma is the second most common cause of blindness in the world
Further development of this method has enabled three-dimensional (3D) reconstruction of the optic nerve head (ONH) and quantification of structures, allowing volumetric quantification of the ONH from a widely available and lowcost imaging source. The advantages of this technique are: (1) objective quantitative measurements of conventional stereo photographs that are otherwise subjective and qualitative, (2) a cost-effective alternative to more sophisticated ocular imaging devices, such as confocal scanning laser ophthalmoscope (CSLO) and optical coherence tomography (OCT), and (3) a bridge between the old legacy data of stereo photographs, which have routinely been collected for clinical evaluation, and the newer technologies (CSLO and OCT)
No consistent pattern in terms of mean and standard deviation was noted among the observers when the results obtained from each of the three individual observers were compared, i. e., comparing seven ONH measurements of one observer with measurements of majority opinion of three individual observers, some measurements were larger and others were smaller
Summary
Glaucoma is the second most common cause of blindness in the world. Excavation of the optic nerve head (ONH) is a typical clinical sign of glaucoma. Stereoscopic disc photography has been used to document structural abnormalities and longitudinal changes in glaucomatous eyes for decades It is the most common method for optic nerve head (ONH) imaging and is used for analysis and diagnosis [4]. Further development of this method has enabled three-dimensional (3D) reconstruction of the ONH and quantification of structures, allowing volumetric quantification of the ONH from a widely available and lowcost imaging source The advantages of this technique are: (1) objective quantitative measurements of conventional stereo photographs that are otherwise subjective and qualitative, (2) a cost-effective alternative to more sophisticated ocular imaging devices, such as confocal scanning laser ophthalmoscope (CSLO) and optical coherence tomography (OCT), and (3) a bridge between the old legacy data of stereo photographs, which have routinely been collected for clinical evaluation, and the newer technologies (CSLO and OCT)
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