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G. M. Somfai, E. Tatrai, B. Varga, D. Cabrera DeBuc; The Effect of Scanning Pitfalls on Boundary Detection Errors and Macular Thickness Measurements of the RTVue MM5 Protocol. Invest. Ophthalmol. Vis. Sci. 2010;51(13):4399.
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© ARVO (1962-2015); The Authors (2016-present)
to investigate whether examination settings of the RTVue FD-OCT have any influence on the errors in retinal boundary detection and retinal thickness measurements.
10 eyes of ten healthy subjects, 10 eyes with diabetic macular edema (DME) and 10 eyes with neovascular AMD were examined with an RTVue OCT device (Optovue Inc, Fremont, CA, USA). MM5 protocol was used in two sessions to scan the macula. For the first session, the device was set 3.5 cm from the eye in order to obtain detectable signal with low fundus image quality ("bad setting") while in the second session a distance of 2.5 cm was set with a good quality fundus image. The signal strength (SSI) value was recorded. The score for inner and outer retinal boundary detection errors (RBDE) was calculated for 5 vertical and five horizontal selected scans of the MM5 grid protocol from each eye for both settings according to a grading system. RBDE scores were also recorded for the peripheral 1.5mm of all scans. The correlation between the SSI and the number of RBDEs was examined. RBDE scores along with regional retinal thickness values between the two sessions were compared. Wilcoxon test was used for the statistical comparisons. All analyses were performed for all participating eyes and for the three subgroups.
SSI was significantly lower with bad settings compared to good settings (63.9±12.0 vs. 68.3±12.2, respectively, p=0.001) and the number of RBDEs was significantly lower with good settings in the overall group along with the subgroup of healthy subjects and eyes with DME (9.1±6.5 vs. 6.8±6.3, p=0.007; 4.4±2.6 vs. 2.5±1.6, p=0.035 and 9.7±3.3 vs. 5.1±3.7, p=0.008, bad vs. good setting, respectively). For these groups, we found significant negative correlation between SSI and the number of RBDEs. Peripheral RBDEs were significantly less with good settings in the overall group and the DME subgroup (4.2±2.8 vs. 2.7±2.6, p=0.001 and 4.1±2.2 vs. 1.4±1.7, p=0.007, respectively). In the remaining central areas of the scans the setting had no influence on RBDEs. Retinal thickness measurements between the two settings were significantly different only in the outer-superior region (R6) in the case of DME eyes.
We showed that SSI improves with better examination settings in the case of FD-OCT and as a result, the number of the RBDEs decreases. However, we found that in spite of this, only minor differences occur in regional retinal thickness measurements.
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