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Utilisation of poor-quality optical coherence tomography scans: adjustment algorithm from the Singapore Epidemiology of Eye Diseases (SEED) study
  1. Sahil Thakur1,
  2. Marco Yu1,
  3. Yih Chung Tham1,2,3,
  4. Shivani Majithia1,
  5. Zhi-Da Soh1,
  6. Xiao Ling Fang1,4,
  7. Carol Cheung5,
  8. Pui Yi Boey2,3,
  9. Tin Aung1,2,3,6,
  10. Tien Yin Wong1,2,3,6,
  11. Ching-Yu Cheng1,2,3,6
  1. 1Singapore Eye Research Institute, Singapore
  2. 2Singapore National Eye Centre, Singapore
  3. 3Ophthalmology & Visual Sciences Academic Clinical Program (Eye ACP), Duke-NUS Medical School, Singapore
  4. 4Department of Ophthalmology, Shanghai Eye Diseases Prevention & Treatment Center/ Shanghai Eye Hospital, Shanghai, China
  5. 5Ophthalmology and Visual Sciences, The Chinese University of Hong Kong, Hong Kong, Hong Kong
  6. 6Ophthalmology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
  1. Correspondence to Dr Ching-Yu Cheng, Ocular Epidemiology Research Group, Singapore Eye Research Institute, Singapore 169856, Singapore; chingyu.cheng{at}


Purpose To evaluate the effect of signal strength (SS) on optical coherence tomography (OCT) parameters, and devise an algorithm to adjust the effect, when acceptable SS cannot be obtained.

Methods 5085 individuals (9582 eyes), aged ≥40 years from the Singapore Epidemiology of Eye Diseases population-based study were included. Everyone underwent a standardised ocular examination and imaging with Cirrus HD-OCT. Effect of SS was evaluated using multiple structural breaks linear mixed-effect models. Expected change for increment in SS between 4 and 10 for individual parameter was calculated. Subsequently we devised and evaluated an algorithm to adjust OCT parameters to higher SS.

Results Average retinal nerve fibre layer (RNFL) thickness showed shift of 4.11 µm from SS of 5 to 6. Above 6, it increased by 1.72 and 3.35 µm to 7 and 8; and by 1.09 µm (per unit increase) above 8 SS. Average ganglion cell-inner plexiform layer (GCIPL) thickness shifted 5.15 µm from SS of 5 to 6. Above 6, increased by 0.94 µm from 7 to 8; and by 0.16 µm (per unit increase) above 8 SS. When compared with reference in an independent test set, the algorithm produced less systemic bias. Algorithm-adjusted average RNFL was 0.549 µm thinner than the reference, while the unadjusted one was 2.841 µm thinner (p<0.001). Algorithm-adjusted and unadjusted average GCIPL was 1.102 µm and 2.228 µm thinner (p<0.001).

Conclusions OCT parameters can be adjusted for poor SS using an algorithm. This can potentially assist in diagnosis and monitoring of glaucoma when scans with acceptable SS cannot be acquired from patients in clinics.

  • glaucoma
  • imaging
  • optic nerve
  • macula

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  • ST and MY are joint first authors.

  • Contributors ST, MY, C-YC, CC, PYB, TA and TYW conceived and designed the study. ST, MY, YCT and C-YC analysed and interpreted the data. ST, MY, YCT, SM, Z-DS and XLF wrote the manuscript. All authors reviewed and approved the final version of the manuscript.

  • Funding This study was supported by the National Medical Research Council, Singapore (grant nos: NMRC/CIRG/1417/2015, NMRC/CIRG/1488/2018; and NMRC/OFLCG/004a/2018).

  • Competing interests None declared.

  • Patient consent for publication Not required.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Data availability statement All data relevant to the study are included in the manuscript or uploaded as supplementary material. However, additional data can be made available on reasonable request to the corresponding author. The algorithm mentioned in the manuscript is available at

  • Supplemental material This content has been supplied by the author(s). It has not been vetted by BMJ Publishing Group Limited (BMJ) and may not have been peer-reviewed. Any opinions or recommendations discussed are solely those of the author(s) and are not endorsed by BMJ. BMJ disclaims all liability and responsibility arising from any reliance placed on the content. Where the content includes any translated material, BMJ does not warrant the accuracy and reliability of the translations (including but not limited to local regulations, clinical guidelines, terminology, drug names and drug dosages), and is not responsible for any error and/or omissions arising from translation and adaptation or otherwise.

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