Low limit for effective signal strength in the Stratus OCT in imperative low signal strength cases.
OBJECTIVE
To determine the lowest limit of signal strength that is still effective for accurate analysis of optic coherence tomography (OCT) values, we investigated the reproducibility of OCT scans by signal strength (SS).


METHODS
A total of 668 subjects were scanned for measurements of retinal nerve fiber layer (RNFL) thickness using the Stratus OCT twice on the same day. The variability of overall RNFL thickness parameters obtained at different SS was analyzed and compared by repeated-measures of ANOVA and Spearman's correlation coefficient. Values of the intraclass correlation coefficient (ICC) and variability (standard deviation) of RNFL thickness were obtained. The false positive ratio was analyzed.


RESULTS
When SS was 3, the variability of RNFL thickness was significantly different (low ICC, high variability) in comparison to when SS was 4 or greater. Significant negative correlations were observed between variability in RNFL thickness and signal strength. The difference of variability of average RNFL thickness between SS 4 (4.94 µm) and SS 6 (4.41 µm) was 0.53 µm.


CONCLUSIONS
Clinically, the difference of variability of average RNFL thickness between SS 4 and SS 6 was quite small. High SS is important, however, when signal strength is low due to uncorrectable factors in patients in need of OCT for glaucoma and retinal disease. Our results suggest that SS 4 is the lowest acceptable limit of signal strength for obtaining reproducible scanning images.
Department of Ophthalmology, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine, Seoul, Korea.
Man Mook
MM
Ha
Joon Mo
JM
Kim
Hyun Joong
HJ
Kim
Ki Ho
KH
Park
Martha
M
Kim
Chul Young
CY
Choi
D000293:Adolescent; D003430:Cross-Sectional Studies; D003937:Diagnosis, Differential; D018450:Disease Progression; D005189:False Positive Reactions; D005260:Female; D005901:Glaucoma / Q000150:complications / Q000175:diagnosis*; D006801:Humans; D008297:Male; D011446:Prospective Studies; D015203:Reproducibility of Results; D012164:Retinal Diseases / Q000175:diagnosis* / Q000209:etiology; D012165:Retinal Ganglion Cells / Q000473:pathology*