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Compressed 3D and 2D digital images versus standard 3D slide film for the evaluation of glaucomatous optic nerve features
  1. Simrenjeet Sandhu1,
  2. Chris Rudnisky1,
  3. Sourabh Arora1,
  4. Faazil Kassam2,
  5. Gordon Douglas2,
  6. Marianne C Edwards1,
  7. Karin Verstraten2,
  8. Beatrice Wong3,
  9. Karim F Damji1
  1. 1 Department of Ophthalmology and Visual Sciences, University of Alberta, Edmonton, Alberta, Canada
  2. 2 Division of Ophthalmology, Department of Surgery, University of Calgary, Calgary, Alberta, Canada
  3. 3 Department of Ophthalmology, Loma Linda University, Loma Linda, California, USA
  1. Correspondence to Dr Simrenjeet Sandhu, Royal Alexandra Hospital, AB T5H 3V9, Canada; simrenje{at}


Synopsis Clinicians can feel confident compressed three-dimensional digital (3DD) and two-dimensional digital (2DD) imaging evaluating important features of glaucomatous disc damage is comparable to the previous gold standard of stereoscopic slide film photography, supporting the use of digital imaging for teleglaucoma applications.

Background/aims To compare the sensitivity and specificity of 3DD and 2DD photography with stereo slide film in detecting glaucomatous optic nerve head features.

Methods This prospective, multireader validation study imaged and compressed glaucomatous, suspicious or normal optic nerves using a ratio of 16:1 into 3DD and 2DD (1024×1280 pixels) and compared both to stereo slide film. The primary outcome was vertical cup-to-disc ratio (VCDR) and secondary outcomes, including disc haemorrhage and notching, were also evaluated. Each format was graded randomly by four glaucoma specialists. A protocol was implemented for harmonising data including consensus-based interpretation as needed.

Results There were 192 eyes imaged with each format. The mean VCDR for slide, 3DD and 2DD was 0.59±0.20, 0.60±0.18 and 0.62±0.17, respectively. The agreement of VCDR for 3DD versus film was κ=0.781 and for 2DD versus film was κ=0.69. Sensitivity (95.2%), specificity (95.2%) and area under the curve (AUC; 0.953) of 3DD imaging to detect notching were better (p=0.03) than for 2DD (90.5%; 88.6%; AUC=0.895). Similarly, sensitivity (77.8%), specificity (98.9%) and AUC (0.883) of 3DD to detect disc haemorrhage were better (p=0.049) than for 2DD (44.4%; 99.5%; AUC=0.72). There was no difference between 3DD and 2DD imaging in detecting disc tilt (p=0.7), peripapillary atrophy (p=0.16), grey crescent (p=0.1) or pallor (p=0.43), although 3D detected sloping better (p=0.013).

Conclusions Both 3DD and 2DD imaging demonstrates excellent reproducibility in comparison to stereo slide film with experts evaluating VCDR, notching and disc haemorrhage. 3DD in this study was slightly more accurate than 2DD for evaluating disc haemorrhage, notching and sloping.

  • Glaucoma
  • Telemedicine

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  • Contributors All coauthors have read the final manuscript within their respective areas of expertise and participated sufficiently in the study to take responsibility for its conclusions. SS, CR, SA, FK: contributions to the design of the work; or interpretation of data for the work; drafting/revising of manuscript; final approval of the version to be published. The first author, SS, has had full access to all data reviewed for this manuscript and takes responsibility for the integrity of the data and affirms that the manuscript is an honest, accurate and transparent account of the study being reported; that no important aspects of the study have been omitted. GD, MCE, KV, BW: contributions to the design of the work; drafting/revising of manuscript; final approval of the version to be published. KFD: contributions to the design of the work; or interpretation of data for the work; final approval of the version to be published.

  • Funding Capital Health Alberta as well as the Canadian National Institute for the Blind (CNIB)-Canadian Glaucoma Research Council provided grant funding for this study.

  • Disclaimer The granting agencies did not participate in design and conduct of the study, collection,management, analysis and interpretation of the data; preparation,review or approval of the manuscript; nor in decision to submit the manuscript for publication.

  • Competing interests None declared.

  • Patient consent Detail has been removed from this case description/these case descriptions to ensure anonymity. The editors and reviewers have seen the detailed information available and are satisfied that the information backs up the case the authors are making.

  • Ethics approval University of Alberta Human Research Ethics Board.

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

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