Silicone oil safety is not only a purity question
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LETTER TO THE EDITOR
Silicone oil safety is not only a purity question Cristina Andrés-Iglesias 1,2
&
José Carlos Pastor 1,2,3,4
Received: 25 August 2020 / Revised: 25 August 2020 / Accepted: 2 October 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Dear Editor, We have read with great interest the paper from Dresp [1] on the analysis of different silicone oils (SiO) in the European market, and we would like to bring some clarifications. For years, low molecular weight components (LMWC) have been considered a source of problems because they can diffuse to the retina causing chronic problems [2]. In 1998, our group stated that these components are related to an increase of clinical side effects [3] without eliciting much interest in the companies. But suddenly, and apparently after problems caused by acute toxicity of perfluoro-octanes and other perfluorocarbon liquids (PFCL) [4–6], companies have become interested in this topic encouraging publications and proposing safety limits for different parameters [7] without having demonstrated a clear relationship between the proposed limits and the clinical or biological safety, repeating the idea that if the product is very pure, safety must be guaranteed. Furthermore, emulsification is not the only problem with the use of SiO, although it is one of the commonest and it seems related to several factors, besides the concentration of LMWC, including the presence of amphiphilic substances into the eye [8]. In a recent meta-analysis that we carried out (submitted for publication), emulsification appears in 30% of the analyzed eyes, with values ranging between 7.5 and 90% depending on what emulsification is considered from a clinical point of view, the amount of time that SiO remains in the eye, the age of the patient, their underlying pathology, and some other clinical characteristics. * Cristina Andrés-Iglesias [email protected] 1
Instituto Universitario de Oftalmobiología Aplicada (IOBA), Eye Institute, University of Valladolid, Valladolid, Spain
2
ISO Committee CTN 91, UNE, Madrid, Spain
3
Expert Panels in the field of Medical Devices, European Commission, Valladolid, Spain
4
Hospital Clínico Universitario, Valladolid, Spain
Thus, the cause of emulsification does not have a simple answer at the moment as it seems to be suggested by Dresp’s paper [1], where any relationship to clinical factors has been omitted. The major problem with SiO is its lipophilic nature, and although it can be logic that the purest the product is the safer for the patient, our real need as clinicians is a different compound that better replicates the characteristics of vitreous [9] or adverse effects will continue to happen. In summary, Dresp’s paper that only considers chemical analysis factors tries to establish a quality reference without taking into account the biological effects that are ultimately our reason for concern as clinicians. Besides, this paper analyzes several commercial brands from the same manufacturer as if were different (obviously having
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