Inadequacies in Uveitis: About the Whimsical Terminology of Bacillary Layer Detachment

Dear Editor, Vogt–Koyanagi–Harada (VKH) disease is a granulomatous panuveitis starting in the posterior choroid.1 The acute uveitic phase of VKH disease is characterized in most cases by secondary exudative retinal detachments due to inflammation resulting in impairment of the function of the retinal pigment epithelium (RPE). The morphology of these detachments is diverse including cases with subretinal fluid and cases with intraretinal fluid which are described in the original publications as intra-photoreceptor separation.2,3 In recent times, a new terminology has been used to describe this well-known phenomenon. The aim of this article is to investigate the genesis and explanation of the new term “bacillary layer detachment” occurring in VKH disease and other outer retinal conditions by performing a critical and chronological review of the literature. Briefly, the phenomenon of intra-photoreceptor separation was originally described by the group of Shoji Kishi in Japan in 20042 and again in 20073 using optical coherence tomography (OCT) technology but this was further described in detail by Ishihara et al. in 2009 in their remarkable article analyzing 10 VKH patients.4 In 2018, the same process was redescribed and given the new name of “bacillary layer detachment (BLD)”.5 It is not rare that medical knowledge or disease processes are episodically rediscovered and redescribed and given new denominations which may result in misunderstanding and confusion. In our previous report, we emphasized specific inadequacies in uveitis, including misnomers, incongruencies, persistence of obsolete terminologies and inappropriate guidelines, treatment inadequacies, and misinterpretations.6 As was demonstrated in this report, a frequent source of such inadequacies is the personal opinions of individual key opinion leaders or groups of influence. An illustrative example of such a process was the case of the “white dot syndromes” terminology.7 This misnomer terminology grouping unrelated diseases based on a common aspect on fundus examination was generated by erroneously including unrelated diseases such as HLA-A29 birdshot retinochoroiditis and multiple evanescent white dot syndrome, and others in the same group, an inadequate intellectual approach.8 Once this opinion was published in a high-impact journal, it was quickly accepted without questioning and propagated at large. Opinion leaders, because of their influence, should be aware of their responsibility and need to be especially cautious before propagating new concepts, interpretations of disease processes, or terminologies. In addition, when presenting new descriptions and explanations of disease mechanisms or new terminologies, previously accomplished and published work in the field should be acknowledged. This avoids any potential confusion by creating new terminology to describe an already existing and well-described phenomenon. As a follow-up to our first report,6 in contrast to previously reported harmful inadequacies in medical practice and knowledge, our aim here was to address the more harmless and whimsical recently introduced terminology of BLD. The invention of this far-fetched term does not have deleterious consequences but rather appears as a peculiarity deserving some attention. As is usually the case when the proposal of a new terminology comes from sufficiently prominent opinion leaders or influential groups, BLD was rapidly and widely adopted without critical evaluation by clinicians at large, becoming a recognized term. However, when the clinician is confronted for the first time with the term, especially when he/she is not someone familiar with publications in the field of retina, he/she will be naturally puzzled and will try to find out why such a term is in use. This was exactly the questioning of some of us when we first found ourselves confronted with this enigmatic term which does not describe the physiopathology of the clinical phenomenon it was designed for. Indeed, the content of the term is not being suggestive of the reality of the disease process relating to a particular damage to the outer retina. We therefore investigated wherefrom such an unfamiliar, arguably imprecise, and apparently ill-suited denomination originated. As indicated, the first precise insights into inflammatory damage of the outer retina using OCT logically came from Japan, as one of the main causes of inflammatory lesions to the outer retina is VKH disease, which is highly prevalent in Japan. Back in 2004, Shoji Kishi and his group already noted that a substantial proportion of acute VKH patients did not have true exudative retinal detachments but had intraretinal separation with intraretinal fluid accumulation.2 In 2007, the same group reported that the outer retina was separated into septae with the posterior wall attached to the RPE.3 In 2009, another Japanese group clearly demonstrated that, besides true exudative retinal detachments, a proportion of VKH patients presented an intraretinal split at the level of the photoreceptors with fluid accumulation comprising pseudo-membranous septae.4 These pseudo-membranous structures, thought to contain inflammation-derived products, responded promptly to high-dose corticosteroids. Consequently, this phenomenon in Japan was since called intra-photoreceptor separation, a straightforward, self-explanatory term that can be universally understood [Figure 1].9 Japanese publications use this term up to date for more than 15 years.4,9,10 Additional similar reports include an article published by Korean colleagues in 2009 speaking of spaces in the photoreceptor layer of VKH patients.11Figure 1: Optical coherence tomography findings of the acute uveitic phase of Vogt–Koyanagi–Harada disease. This case shows the difference between exudative retinal detachments and intra-photoreceptor detachment/separation. RPE: Retinal pigment epitheliumFourteen years after its first mention, this phenomenon was redescribed and published as a new OCT finding and given the name of BLD.5 The origin of this exotic name awakens one’s curiosity. It is explained that the term goes back to the deep past, 17th-century German anatomy literature, from where the term of “stratum bacillosum” or bacillary layer emerged in place of the photoreceptor layer which indeed sounds much better.12 Indeed, the term BLD is much more fashionable than the clinically descriptive term of intra-photoreceptor detachment/separation which nevertheless has the advantage of describing the pathophysiological process, useful for clinicians not specialized in retinal matters. As is usually the case when such novelties are generated by influential groups, the term becomes widely used and has definitively been integrated into the ophthalmological vocabulary, now widely committed to using a new, fanciful, nondescriptive term applied to a previously known disease mechanism. Indeed, a recent PubMed search listed as many as 89 articles under the heading of “bacillary layer detachment”, many of them initially coming from the same group of authors. This trend has come to the point that the entire ophthalmological community has been formatted to use the term BLD, so much so that when using the original term in an article, the authors are invited by the reviewers to use the “correct” terminology.13 For the sake of immediate understanding of what is talked about, we are inclined to use the original term of intra-photoreceptor detachment or separation because, although BLD may be a trendy, intriguing, and surprising term, it does not factually describe the mechanism it is supposed to characterize, while the original term is self-explanatory and understood by all. BLD can therefore be included as a curious inconsistency with harmless consequences. In fine, one simple aim of our move was also to ensure that the recognition of an advancement in medical knowledge goes to those who are at its origin. Of course, for the sake of understanding, the use of the original descriptive term is preferable, and this is what we recommend. However, we know that once an inappropriate term has found its way into medical terminology, it is quasi-impossible to get rid of it. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.

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