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Effect of posterior vitreous detachment on treat-and-extend versus monthly ranibizumab for neovascular age-related macular degeneration
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  • Published on:
    Response to Svasti-Salee, Snead and Alexander
    • Sebastian M. Waldstein, Retina Specialist Medical University of Vienna
    • Other Contributors:
      • Sophie Riedl, Registrar
      • Bianca S. Gerendas, Retina Specialist
      • Ursula Schmidt-Erfurth, Professor and Chair

    Dear Editor,

    We thank Svasti-Salee, Snead and Alexander [1] for their interest in our study and their comment regarding the reliability of spectral domain optical coherence tomography (SD-OCT) in differentiating a completely attached hyaloid versus complete posterior vitreous detachment (PVD).

    To address the author’s question, in our post-hoc analysis, only SD-OCT was used to diagnose PVD status. A slit-lamp examination specifically assessing for PVD was not performed per protocol in the TREND study, [2] therefore data other than SD-OCT were not available for post-hoc analysis.

    The accepted clinical methods to determine PVD include slit-lamp examination, dynamic ultrasonography and SD-OCT, while previous generations of OCT (time-domain OCT) potentially offered insufficient resolution and field of view. Of those methods, SD-OCT has the main advantage of being operator independent and allowing systematic, standardized evaluation in a reading center setting. The approach chosen for the analysis of the TREND dataset has been repeatedly performed in several prior studies, with similar outcome data. [3-5]

    A recent study cited by the authors [6] reports that PVD status on SD-OCT did not correlate well to intraoperative findings when patients underwent vitrectomy. However, vitrectomy surgery is performed in patients with vitreomacular interface disease, where often a multi-layered posterior vitreous cortex cleaving into separate planes is found, making...

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    Conflict of Interest:
    None declared.
  • Published on:
    Response to 'Effect of posterior vitreous detachment on treat-and-extend versus monthly ranibizumab for neovascular age-related macular degeneration
    • Carl R Svasti-Salee, Ophthalmologist Addenbrooke's Hospital, Cambridge University Hospitals NHS Foundation Trust
    • Other Contributors:
      • Martin P Snead, Vitreoretinal Surgeon
      • Philip Alexander, Vitreoretinal Surgeon

    Dear Editor,

    We read with interest the post-hoc study by Waldstein and colleagues concerning the impact of posterior vitreous detachment (PVD) on the efficacy of anti-VEGF treatment in neovascular age-related macular degeneration (AMD). However, the reliability of spectral-domain optical coherence tomography (SD-OCT) in confirming PVD status, upon which the findings of this study are dependent, is questionable.[1, 2] In particular, OCT is poor at distinguishing between fully attached vitreous and complete PVD.

    Hwang et al recently reported limited sensitivity of SD-OCT in detecting complete PVD when compared to clinical findings at the time of vitrectomy.[1] It was found that among patients awaiting vitrectomy, OCT diagnosis of complete PVD (based on the absence of visible posterior vitreous cortex or a premacular bursa on SD-OCT) had a positive predictive value of just 53% when compared to intra-operative findings.

    PVD remains a clinical diagnosis that is based on the identification of the posterior hyaloid membrane (PHM), a diaphanous, wrinkled film observable during biomicroscopic examination. The Weiss ring which it incorporates is a more variable and less reliable confirmatory sign of PHM detachment from the optic nerve head. The visible PHM is a consistent clinical finding in patients with PVD and correlates histopathologically with a type IV collagen basement membrane which begins life attached to the retina as the internal limiting membrane.[3...

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    Conflict of Interest:
    None declared.