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Factors Affecting Cirrus-HD OCT Optic Disc Scan Quality: A Review with Case Examples.

Hardin JS, Taibbi G, Nelson SC, Chao D, Vizzeri G - J Ophthalmol (2015)

Bottom Line: However, recent evidence indicates that OCT scan artifacts are frequently encountered in clinical practice.Therefore, adequate knowledge of various imaging artifacts is necessary.In this work, we describe several factors affecting Cirrus HD-OCT optic disc scan quality and their effects on measurement variability.

View Article: PubMed Central - PubMed

Affiliation: Department of Ophthalmology and Visual Sciences, The University of Texas Medical Branch at Galveston, Galveston, TX 77550, USA.

ABSTRACT
Spectral-domain OCT is an established tool to assist clinicians in detecting glaucoma and monitor disease progression. The widespread use of this imaging modality is due, at least in part, to continuous hardware and software advancements. However, recent evidence indicates that OCT scan artifacts are frequently encountered in clinical practice. Poor image quality invariably challenges the interpretation of test results, with potential implications for the care of glaucoma patients. Therefore, adequate knowledge of various imaging artifacts is necessary. In this work, we describe several factors affecting Cirrus HD-OCT optic disc scan quality and their effects on measurement variability.

No MeSH data available.


Related in: MedlinePlus

Floater overlying the optic disc region. Cirrus HD-OCT RNFL deviation maps ((a)-(b)), OCT tomograms ((c)-(d)), realigned en-face images (e), and printout results (f) from two right optic disc scans collected on the same day. In the first scan, the floater was located between the optic disc and the scan circle ((a) and (c), arrow). In the second scan, it was automatically included in the optic disc area ((b) and (d), arrow). The nasal margin of the floater was mistakenly interpreted as the optic nerve head neural canal opening ((d) asterisk), leading to increased rim and disc areas (f) and to inferonasal displacement of the optic disc center and the scan circle ((e) purple scan circle). Note the retinal nerve fiber layer thickening in the superotemporal clock hours, closer to the optic disc margin, and the corresponding thinning of the inferonasal clock hours, moved further away from the optic disc. SS: signal strength.
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fig3: Floater overlying the optic disc region. Cirrus HD-OCT RNFL deviation maps ((a)-(b)), OCT tomograms ((c)-(d)), realigned en-face images (e), and printout results (f) from two right optic disc scans collected on the same day. In the first scan, the floater was located between the optic disc and the scan circle ((a) and (c), arrow). In the second scan, it was automatically included in the optic disc area ((b) and (d), arrow). The nasal margin of the floater was mistakenly interpreted as the optic nerve head neural canal opening ((d) asterisk), leading to increased rim and disc areas (f) and to inferonasal displacement of the optic disc center and the scan circle ((e) purple scan circle). Note the retinal nerve fiber layer thickening in the superotemporal clock hours, closer to the optic disc margin, and the corresponding thinning of the inferonasal clock hours, moved further away from the optic disc. SS: signal strength.

Mentions: Floaters and other vitreous opacities have been documented in Cirrus HD-OCT macular and optic disc scans [22, 23]. These opacities may decrease scan quality by interfering with the light beam path, as described above. However, the effects on OCT measures are more closely related to their position within the scan area. When a floater is located on the scan circle (Figure 2(b)), a classical vertical shadow of signal attenuation/interruption is visible in the corresponding area of the circular tomogram (Figure 2(c)). Caution is recommended when interpreting the results, as the presence of the floater may mimic initial glaucomatous damage or falsely suggest thinning of a preexisting RNFL defect, particularly when it is located superotemporally or inferotemporally (Figure 2(d)). Although in most cases this artifact is easily identifiable on the printout, floaters near the optic disc area may remain undetected due to the presence of major retinal vessels and other graphical items displayed on the en-face image (Figure 3). Therefore, assessment of the tomograms intersecting the optic disc is warranted. In the example presented in Figure 3(b), a floater was mistakenly incorporated as part of the inferonasal optic disc area by the automated algorithm delineating the disc margins. Along with changes to optic disc parameters, the focal enlargement of the optic disc area dislocated the optic disc center and the scan circle inferonasally, producing major changes in RNFL thickness and classification results (Figures 3(e)-3(f)) [22].


Factors Affecting Cirrus-HD OCT Optic Disc Scan Quality: A Review with Case Examples.

Hardin JS, Taibbi G, Nelson SC, Chao D, Vizzeri G - J Ophthalmol (2015)

Floater overlying the optic disc region. Cirrus HD-OCT RNFL deviation maps ((a)-(b)), OCT tomograms ((c)-(d)), realigned en-face images (e), and printout results (f) from two right optic disc scans collected on the same day. In the first scan, the floater was located between the optic disc and the scan circle ((a) and (c), arrow). In the second scan, it was automatically included in the optic disc area ((b) and (d), arrow). The nasal margin of the floater was mistakenly interpreted as the optic nerve head neural canal opening ((d) asterisk), leading to increased rim and disc areas (f) and to inferonasal displacement of the optic disc center and the scan circle ((e) purple scan circle). Note the retinal nerve fiber layer thickening in the superotemporal clock hours, closer to the optic disc margin, and the corresponding thinning of the inferonasal clock hours, moved further away from the optic disc. SS: signal strength.
© Copyright Policy - open-access
Related In: Results  -  Collection

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fig3: Floater overlying the optic disc region. Cirrus HD-OCT RNFL deviation maps ((a)-(b)), OCT tomograms ((c)-(d)), realigned en-face images (e), and printout results (f) from two right optic disc scans collected on the same day. In the first scan, the floater was located between the optic disc and the scan circle ((a) and (c), arrow). In the second scan, it was automatically included in the optic disc area ((b) and (d), arrow). The nasal margin of the floater was mistakenly interpreted as the optic nerve head neural canal opening ((d) asterisk), leading to increased rim and disc areas (f) and to inferonasal displacement of the optic disc center and the scan circle ((e) purple scan circle). Note the retinal nerve fiber layer thickening in the superotemporal clock hours, closer to the optic disc margin, and the corresponding thinning of the inferonasal clock hours, moved further away from the optic disc. SS: signal strength.
Mentions: Floaters and other vitreous opacities have been documented in Cirrus HD-OCT macular and optic disc scans [22, 23]. These opacities may decrease scan quality by interfering with the light beam path, as described above. However, the effects on OCT measures are more closely related to their position within the scan area. When a floater is located on the scan circle (Figure 2(b)), a classical vertical shadow of signal attenuation/interruption is visible in the corresponding area of the circular tomogram (Figure 2(c)). Caution is recommended when interpreting the results, as the presence of the floater may mimic initial glaucomatous damage or falsely suggest thinning of a preexisting RNFL defect, particularly when it is located superotemporally or inferotemporally (Figure 2(d)). Although in most cases this artifact is easily identifiable on the printout, floaters near the optic disc area may remain undetected due to the presence of major retinal vessels and other graphical items displayed on the en-face image (Figure 3). Therefore, assessment of the tomograms intersecting the optic disc is warranted. In the example presented in Figure 3(b), a floater was mistakenly incorporated as part of the inferonasal optic disc area by the automated algorithm delineating the disc margins. Along with changes to optic disc parameters, the focal enlargement of the optic disc area dislocated the optic disc center and the scan circle inferonasally, producing major changes in RNFL thickness and classification results (Figures 3(e)-3(f)) [22].

Bottom Line: However, recent evidence indicates that OCT scan artifacts are frequently encountered in clinical practice.Therefore, adequate knowledge of various imaging artifacts is necessary.In this work, we describe several factors affecting Cirrus HD-OCT optic disc scan quality and their effects on measurement variability.

View Article: PubMed Central - PubMed

Affiliation: Department of Ophthalmology and Visual Sciences, The University of Texas Medical Branch at Galveston, Galveston, TX 77550, USA.

ABSTRACT
Spectral-domain OCT is an established tool to assist clinicians in detecting glaucoma and monitor disease progression. The widespread use of this imaging modality is due, at least in part, to continuous hardware and software advancements. However, recent evidence indicates that OCT scan artifacts are frequently encountered in clinical practice. Poor image quality invariably challenges the interpretation of test results, with potential implications for the care of glaucoma patients. Therefore, adequate knowledge of various imaging artifacts is necessary. In this work, we describe several factors affecting Cirrus HD-OCT optic disc scan quality and their effects on measurement variability.

No MeSH data available.


Related in: MedlinePlus