J Korean Ophthalmol Soc.  2016 Jul;57(7):1087-1092. 10.3341/jkos.2016.57.7.1087.

The Effect of Machine Aging on the Measurements of Optical Coherency Tomography

• Kim MS
• Kim DY
• Jo YJ
• Kim JY

• KMID: 2317569
• DOI: http://doi.org/10.3341/jkos.2016.57.7.1087

Abstract

PURPOSE
To evaluate the effect of instrument aging on optical coherence tomography (OCT) measurements.
METHODS
Single eyes of 60 healthy participants (60 eyes) aged 20-30 years were examined twice using a 5-year-old OCT instrument and a new OCT instrument (Carl Zeiss Meditec, Dublin, CA, USA). The measurements and changes in signal strength were investigated using both instruments.
RESULTS
The signal strengths of the new and aged instruments were 8.6 ± 0.8 and 5.0 ± 1.0, respectively, which was a statistically significant difference (p < 0.001). In addition, the central macular thicknesses (CMT) of the new and aged instruments were 201.1 ± 16.1 µm and 210.3 ± 16.0 µm, respectively. The thickness was significantly greater using the aged instrument (p < 0.001). Repeated measurements within the same eye were compared, and the difference in CMT was 3.2 using the new instrument and 10.5 using the aged instrument (p < 0.05). The intraclass correlation coefficient (ICC) was compared to evaluate the reproducibility of each instrument. The ICC values of nine areas of Early Treatment Diabetic Retinopathy Study in the aged instrument were 0.371-0.872, indicating low reproducibility. However, the new instrument showed high reproducibility with values of 0.806-0.947.
CONCLUSIONS
Higher signal strength and lower CMT were observed using the new instrument compared to the aged instrument. Additionally, there were no differences in signal strength errors between the instruments. However, the error in CMT measured using the new instrument was significantly smaller compared to that using the aged instrument. Therefore, the effect of instrument aging should be accounted for in analyses of OCT measurements.

Keyword

Aging of optical coherence tomography (OCT); Central macular thickness; OCT measurements; Signal strength

MeSH Terms

Aging*
Child, Preschool
Diabetic Retinopathy
Healthy Volunteers
Humans
Tomography, Optical Coherence

Figure

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  Figure 1. The nine Early Treatment Diabetic Retinopathy Study (ETDRS) subfield area. The diameters of central circle, inner ring, and outer ring were 1 mm, 3 mm, and 6 mm, respectively. F = fovea; SI = superior inner; TI = temporal inner; II = inferior inner; NI = nasal inner; SO = superior outer; TO = temporal outer; IO = inferior outer; NO = nasal outer.

• 

  Figure 2. Representative images from one patient using aged instrument and new instrument. (A) Signal strengths measured using the aged instrument (left) and the new instrument (right). (B) Fast macular thickness maps measured using the old instrument (left) and the new instrument (right). OCT = optical coherence tomography.

Reference

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