Subretinal silicone oil: OCT imaging findings and surgical management of a rare and unusual iatrogenic complication of retinal detachment surgery

Background

Silicone oil is commonly used in retinal detachment surgery as a long-term tamponade and has a number of recognised complications including band keratopathy, cataract and raised intraocular pressure. Small droplets of emulsified silicone oil have been reported to migrate into the intraretinal and subretinal spaces. However, there is a paucity of reports describing large fresh bubbles of retained silicone oil under the retina immediately after retinal detachment surgery, such as in this case.

It is not entirely clear how this occurred in our patient, but we hypothesise why and explain our surgical approach for removing the oil bubbles.

Case presentation

A man in his 50s was referred to eye casualty by his optician complaining of floaters and foggy vision in his right eye. He was a fit and well man with no significant previous medical or ophthalmic history.

On examination, his visual acuity was reduced to 1.24 logMAR at 2 m compared with 0.00 logMAR in his left eye. The patient was phakic with no lens opacity. He had tobacco dust in the vitreous of his right eye and fundus examination revealed a macular off retinal detachment with a superonasal horseshoe tear. Examination of his left fundus was unremarkable.

He underwent a right pars plana vitrectomy using the 25 Gauge Alcon Constellation system (Alcon, Fort Worth, Texas). After routine vitrectomy, retinal breaks were identified and marked with diathermy. Subretinal fluid was then drained prior to endolaser retinopexy around the retinal breaks. Fluid air exchange was performed and while completing the peripheral endolaser, the infusion line was displaced and the eye became hypotonous. The lens became temporarily opacified impeding the view of the retina. As the view cleared a large macular sparing suprachoroidal haemorrhage was noted. Silicone oil 1000 cs was inserted as tamponade and all ports were sutured. At the end of the surgery, the retina appeared flat.

When the patient was reviewed the following day his vision was 1.0 logMAR in the right eye, intraocular pressure was 13 mm Hg and the suprachoroidal haemorrhage had almost fully resolved aside from a small residual area superiorly. The retina was otherwise flat with an underfill of silicone oil at 80%. However, some bubbles were noted under the retina in a number of locations, the largest of which was just below the superotemporal arcade.

Investigations

Optos colour images (Optos, California) (figure 1) and Heidelberg optical coherence tomography (OCT) images (Heidelberg, Germany) (figure 2) of the right eye on day 1 postoperatively demonstrate the subretinal bubbles (arrows). The OCT (figure 2) demonstrates a large convex subretinal elevation with hyporeflective choroidal shadow at the edges of the bubble (arrow). There are also a number of smaller subretinal bubbles seen around the posterior pole (arrows).

Differential diagnosis

Due to the morphology of the bubble on OCT, we suspected that this was retained silicone oil. Retained perflourocarbon liquid (PFCL) can also have a similar appearance but this was not used during the surgery. Subretinal fluid would not form a convex bubble with this morphology.

Treatment

We initially decided to monitor the subretinal bubbles to allow the eye time to settle and to see whether they migrated or dispersed. Follow-up OCT and OPTOS images 3 weeks later demonstrated persistence of the subretinal bubbles and no migration or shrinkage. Due to their proximity to the macular and fears regarding possible toxicity to the retina, it was necessary to remove them. We, therefore, listed the patient for removal of silicone oil and removal of the sub retinal retained bubbles.

He had surgery 8 weeks after the initial surgery. Images show intraoperative findings (figure 3). A small drainage retinotomy was made over the main bubble, and oil bubbles were visibly released, confirming our suspicions that the liquid was retained silicone oil. A further retinotomy was made over the other large inferior retained oil bubble which was successfully drained. Fluid air exchange successfully flattened the retina and a temporary gas tamponade was used.

Outcome and follow-up

At 7 weeks post removal of silicone oil, vision in the right eye was 0.5 logMAR unaided. The patient had developed a grade 2 posterior subcapsular cataract. Despite the cataract, the fundal view was still adequate to ascertain that the retina was flat and all gas had dispersed from the vitreous cavity. Imaging shows resolution of the two large subretinal oil bubbles (figure 4). The patient was listed for cataract extraction to be done approximately 3 months later.