With the wide application of PFCL and silicone oil in retinal detachment repair, the frequency of sticky silicone oil occurrence is increasing. Ghoraba et al. suggested that the formation of sticky silicone oil bubbles was not related to the viscosity, duration, or brand of silicone oil used; their results indicated that this phenomenon was only related to the usage of PFCL. Notably, PFCL application can reduce the surface tension of the oil interface, forming a hyper-viscous solution. The cohesion of silicone oil is lower than its adhesive force, so the removal of sticky silicone oil from the retinal surface may be difficult due to changes in its properties.[10, 12] An in vitro experiment by Romano et al. showed that the presence of PFCL can cause the silicone oil mixture to become opaque and viscous. Consistent with the previous findings, the formation of sticky silicone oil bubbles in our study was independent of the duration of silicone oil tamponade. All patients in our study had used PFCL, which was not completely cleared, leading to the formation of sticky silicone oil bubbles.
Several surgical techniques have been reported for the successful removal of sticky silicone oil bubbles, such as passive removal in 23-gauge transconjunctival vitrectomy, 25-gauge sutureless system, and 20-gauge cannula. However, these techniques can cause sudden collapse of the eyeball and lead to retinal redetachment. Here, we introduced a less invasive and more efficient method for active removal of sticky silicone oil bubbles with a modified 22-gauge venous indwelling cannula. The use of a large-bore instrument during manual aspiration may cause iatrogenic injuries. We implemented a 22-gauge vacuum soft needle with a foot pedal to control active aspiration on the vitrectomy machine; this generated suction power on sticky silicone oil bubbles, thereby minimising damage to the incision and retina. Using a 1-ml syringe for control improved stability and operator convenience. The entire system can be easily assembled in a few minutes, thereby enabling safe and simple removal of sticky silicone oil.
After most silicone oil bubbles have been removed, tiny oil bubble closely adhere to the retinal surface. Forceful aspiration to remove sticky silicone oil bubbles can lead to peripheral retinal tears and choroidal haemorrhages, which some doctors may not actively manage. Some studies have shown that silicone oil due to the concentration of low molecular weight components and amphiphilic substances has toxic effects on the anterior segment, trabecular meshwork, ganglion cell complex, and retinal pigment epithelium.[17, 18] Veckeneer et al. reported that the residue caused relative scotomata in four patients. In two of those patients, the symptoms were temporary because the sticky silicone oil bubbles spontaneously detached and migrated upwards to the 12 o’clock position. Parafoveal bubbles caused moderate visual symptoms, whereas foveal bubbles led to central vision loss and scotoma.[9, 10] In our study, the postoperative BCVA was better in the ILM peeling group than in the non-ILM peeling group. In one patient, postoperative BCVA improved to 1.0 (Fig. 4). Therefore, we recommend ILM peeling to remove smaller oil bubbles that are strongly adhered to the retina. This method improves postoperative BCVA, while avoiding the toxicity of silicone oil and the possibility of secondary macular membrane formation.
The main postoperative complication was iatrogenic parafoveal damage to the retinal neuroepithelial layer. In all patients, most sticky silicone oil bubbles were removed by using a 22-gauge venous indwelling cannula or a 23-gauge vitreous cutter, both of which were placed at a safe distance from the retina and associated with a low rate of retinal damage. In patients without ILM peeling, silicone-tipped flute needles were used to remove oil bubbles adhered to the retinal surface. This procedure could cause retinal damage; notably, the only two patients with iatrogenic damage in our study were both treated with a flute needle. The incidence of retinal injury in the group using flute needles (28.6%) tended to be higher than that in the group not using flute needles (0.0%); however, this difference was not statistically significant, presumably because of the small number of included patients. Temporary hypotony was a minor postoperative complication. The mechanism of hypotony is not well understood, although underlying pathologic changes in the ciliary body or surgical procedures may contribute to the development of postoperative transient hypotony by reducing aqueous production, thereby creating aqueous outflow. The range of hypotony following silicone oil removal is 2–39%, some of which is transient and recovers within weeks without any impact on BCVA.[20, 21]
There were some limitations in our study, such as its small sample size; retrospective, uncontrolled design; and relatively short follow-up duration. Further investigations should include larger numbers of patients and longer follow-up to confirm the efficiency and safety of the methods described here.
In summary, we introduced safe and efficient methods for the removal of distinct types of sticky silicone oil bubbles adhered to the retinal surface. A 22-gauge venous indwelling cannula was a simple and safe approach for the removal of large sticky silicone oil bubbles, while small residual sticky silicone oil bubbles could be completely removed by ILM peeling.