This report is of our intraoperative suspicion of a separation of the inner and outer retina as a cause of tractional retinal laxity, which was confirmed using iOCT. Preoperative OCT often shows tractional retinoschisis in patients with PDR and TRD [4, 6]. Kim et al. reported that diabetic tractional retinal elevation may progress to TRD or tractional retinoschisis [4]. Moreover, a histopathological study showed that retinoschisis is combined with retinal detachment [7]. Specifically, the study investigated four globes with elevated retina with PDR, in which two of four cases were complicated with retinal detachment and retinal elevation, whereas the other two cases were combined only with retinoschisis [7]. In this case, the area of elevated retina was large, and detached retina was possibly associated with retinoschisis. Although we cannot rule out the possibility that the congenital schisis is complicated by FVM, providing definitive evidence for this is difficult. Moreover, given that there was no prior diagnosis of congenital schisis at the previous institution, it is more probable that the schisis is due to FVM rather than being congenital.
Regarding surgery for PDR, a procedure to remove FVM is the most difficult for tractional and rhegmatogenous retinal detachment, because the detached retina is pressed against the FVM. Thus, a vitreoretinal instrument such as scissors or cutter would be unlikely inserted toward the space of retinoschisis during surgery; however, in this case, retinal holes near the arcade were merged into the site of retinoschisis. Moreover, the retinal holes may have been connected to the space of retinoschisis, and the space between the retina and FVM may have been smaller than the space between the retinoschisis. Hence, membrane delamination presumably extended stray into the space between the inner and outer retinal layers through retinoschisis and multiple retinal holes. The patient had sclerosed vessels in all quadrants implying ischemic atrophic retina. Presence of such retina with underlying tractional schisis can be a risk factor for inner-outer retina separation during delamination. It remains to be determined whether segmentation rather than peeling or controlled bimanual peeling in the case of sticky membranes, might be preferable. Additionally, it should be noted that even highly skilled retinal surgeons can encounter issues, one of which may be caused by indiscriminately pulling on the membrane.
To prevent postoperative TRD, we removed the inner retina within the separation between inner and outer retina. In congenital schisis, the inner schisis wall must be removed because the residual posterior cortical vitreous overlying the inner schisis will cause TRD [8]. Given the elevated perceived risk of developing postoperative proliferative membranes in severe PDR compared to other conditions, the inner schisis should be removed, as is done in cases of congenital schisis.
However, as evidenced by our case, unintentional penetration can occur into the space between the inner and outer retina layers. If such intrusion goes unnoticed early on, it could lead to the enlargement of disconnect between the inner and outer layers, resulting in visual deterioration, thus utmost caution is imperative.
Therefore, in cases where tractional retinoschisis due to FVM in PDR is combined with retinal holes, careful membrane delamination is necessary. In such cases, it may be preferable to avoid delamination altogether, opting instead for segmentation, or to perform controlled bimanual delamination when the membranes are densely adherent to the underlying retina. As previously reported, Visual function may benefit from vitreous surgery despite residual macular abnormalities in some cases [9]. Therefore, opting for segmentation alone without forcibly peeling can also be considered a viable option. And the detailed evaluation of space (e.g., between inner and outer retina or between FVM and retina) is crucial during the surgery.
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