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Acellular nerve allografts in corneal neurotisation: an inappropriate choice
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  • Published on:
    Acellular nerve allografts are viable alternatives to nerve autografts in corneal neurotization
    • ILYA M LEYNGOLD, Oculoplastic Surgeon Duke University Medical Center, Department of Ophthalmology

    There is no unified consensus in the peripheral nerve literature regarding the optimum type of interposition nerve graft for target tissue reinnervation. There are multiple well-designed peer reviewed studies by leading experts in peripheral nerve surgery supporting the use of acellular nerve allografts (ANAs) as viable alternatives to nerve autografts at various gap lengths [1-3]. While there are no trials directly comparing the use of ANAs to nerve autografts in corneal neurotization, Avance® allografts have now become “on label” for corneal neurotization given the successful clinical outcomes reported by several tertiary care centers [4].

    In comparing the study by Catapano et al. to the study by Leyngold et al. it is important to note that the average follow up in the former was 24 months whereas it was only 6 months in the latter [4,5]. In addition, 88% of the patients in the paper by Catapano et al. were under 18 years of age vs. 14% in the paper by Leyngold et al. As stated in my previous correspondence, Park et al has shown that pediatric age is correlated to improved results in corneal neurotization irrespective of the technique [6]. Catapano et al. noted continued improvement in central corneal sensation (CCS) up to two years postoperatively. The reported CCS at 6 months postoperatively was only 30.0±26.8mm with a significant number (44%) of patients in their study having CCS at or below 10mm and peripheral corneal sensation (PCS) at or below 30mm at that...

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    Conflict of Interest:
    None declared.
  • Published on:
    Clinical Evidence Points to a Higher Risk of Procedural Failure with Acellular Nerve Allograft Use in Corneal Neurotisation
    • Nate Jowett, Facial Plastic Surgeon Massachusetts Eye and Ear / Harvard Medical School
    • Other Contributors:
      • Roberto Pineda II, Corneal Surgeon

    Dr. Leyngold states we ‘fail to support [our] viewpoint with peer reviewed studies.’ Our position against the use of acellular nerve allografts (ANAs) in corneal neurotisation was grounded on robust evidence from basic science literature demonstrating their inferior performance relative to autografts for large gap nerve repair. No clinical trial comparing the two techniques exists, and in our opinion there lacks the necessary equipoise to perform such a study.

    The regeneration-restrictive properties of long-segment ANAs renders them unsuitable for use in directing sensory axons to the cornea. The largest single-centre study on Avance® ANA use for peripheral nerve repair demonstrated meaningful recovery in only 54% of cases where allografts longer than 50 mm were employed [1]. Remarkably, exploitation of the suboptimal capacity of ANAs to support nerve regeneration has been proposed as a means to inhibit axon growth in the surgical management of painful neuromas [2].

    In his defence of off-label use of Avance® allografts in corneal neurotisation, Dr. Leyngold cites his case-series wherein sensory improvement of 35 mm or more was documented in two of seven eyes (29%). In contrast, Catapano et al. noted sensory improvement of 35 mm or more in 16 of 18 cases (89%) where nerve autografts were employed to route healthy trigeminal sensory axons to anaesthetic corneas [3]. In our own experience, we have yet to encounter a suboptimal neurotization outcome with use of n...

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    Conflict of Interest:
    None declared.
  • Published on:
    Efficacy of acellular nerve allografts in corneal neurotisation: an objective evaluation of the existing evidence
    • ILYA M LEYNGOLD, Oculoplastic Surgeon Duke University Medical Center, Department of Ophthalmology

    Given the lack of level 1 evidence there is no unified consensus among peripheral nerve experts on the optimum type of interposition nerve graft for target tissue reinnervation. There are multiple peer reviewed studies by leading experts in peripheral nerve surgery supporting the use of acellular nerve allografts (ANAs) as viable alternatives for peripheral nerve reconstruction at various gap lengths [1-3]. Moreover, as the authors correctly point out in their correspondence, no trials exist comparing the use of ANAs to nerve autografts in corneal neurotization, nullifying their claim of nerve autograft superiority for this procedure. Of note, Avance® allografts have become “on label” for corneal neurotization since my last correspondence.

    In comparing the study by Catapano et al to the study by Leyngold et al it is important to note that the average follow up in the former was 24 months whereas it was only 6 months in the latter [4,5]. In addition, 88% of the patients in the paper by Catapano et al were under 18 years of age. As stated in my previous correspondence, Park et al has shown that pediatric age is correlated to improved results in corneal neurotization irrespective of the technique [6]. Catapano et al noted continued improvement in central corneal sensation (CCS) up to two years postoperatively. Catapano et al reported mean CCS at 30.0±26.8mm at 6 months postoperatively, with a significant number (44%) of patients in their study having CCS at or below 10...

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    Conflict of Interest:
    None declared.