Discussion
retinal rigidity, Müller cell foot plate avulsion, paracentral scotomata, temporal VF defects, retinal injury, trauma
RETINA
This is the first proof-of-concept RCT assessing a newly developed types of ILM peeling forceps as compared with a standard one with a wide range of anatomical and functional endpoints. As a proof-of-concept study, it was successful, and the outcomes’ validity was strengthened by the trial design with robust randomisation and masking processes. Our trial provides a blue-print for future studies with outcome methodology and estimates that can be used to assess sample size to detect specific differences with appropriate sample sizes. Importantly, although RCT is a well-known tool for comparison, no previous study compared different types of ILM forceps, and no study design or set of outcomes has been previously validated to this aim.We particularly focused on various endpoints to assess IR changes which occur consequently to ILM peeling and could be exacerbated by surgical trauma. The ILM is a < 10-μm thick, transparent membrane, forming the inner boundary of the retina. Although thin, its mechanical strength is in the megapascal range similar to articular cartilage and about 1000-fold stronger than the cellular layers, forming at least 50% of the retinal rigidity [Inner retinal layer changes occurring after ILM peeling can be focal related to direct instrument trauma or in a regular characteristic pattern as a consequence of Müller cell foot plate avulsion, termed DONFL [It has been suggested that alternative ILM peeling techniques may be associated with varying degrees of retinal injury and recovery [The functional consequences of the iatrogenic IR trauma and post-ILM peeling anatomical changes are uncertain. Some authors described paracentral scotomata, temporal VF defects and reduced retinal sensitivity after ILM peeling whilst others have not, and a DONFL appearance is not thought to have any functional consequences [We attempted to control for several other factors potentially related to IR changes. Vital dyes may influence the iatrogenic stress exerted on the retinal tissue [There are several limitations to our study. Importantly, it was designed as a proof-of-concept study and therefore not powered to detect a specific level of difference between the two groups. Inter-surgeon variability could have masked clearer differences. Finally, we did not perform microperimetry and analysed the VFs via MD score; therefore, focal defects may have been missed. Assessing microperimetry at the grasp sites themselves could be analysed in future studies.In conclusion, we successfully conducted a first-in-class masked randomised proof-of-concept study of two different forceps types used for ILM peeling. The findings do not support any clear benefit of etched-tip forceps over standard forceps during ILM peeling, but it is important to note that being a proof-of-concept study, the sample size was not chosen to assess any one endpoint. The trial design and data produced can serve as a model for future trials with appropriate sample sizes.