Trapped Pre-Macular Bubble of Octafluoropropane Gas Masquerading as Retained Submacular Perfluorocarbon Liquid Open Access

Although first described in 1973 [1], expansile gases are now commonly used during primary retinal detachment repair, and longer-acting tamponade agents such as octafluoropropane (C₃F₈) can be used in the treatment of giant retinal tear-associated retinal detachment when the macula is still preserved [2]. Perfluorocarbon liquid (PFCL) represents a significant adjunct in the treatment of the aforementioned type of retinal detachment and although its intraoperative role is important, several intra- and post-operative complications associated with its use have been reported in the literature [3]. These include post-operative PFCL retention, retinal slippage, and toxicity [4].

We herein demonstrate, with the aid of retinal imaging, an abnormal post-operative macular appearance caused by the presence of a “fragmented” pre-retinal bubble of C₃F₈ masquerading as retained subretinal PFCL.

A 60-year-old man presented to our institution with a right macula-off rhegmatogenous retinal detachment caused by a temporal giant retinal tear. Visual acuity was hand movements in the affected eye. He underwent a three-port 23-gauge pars plana vitrectomy with the use of PFCL and an endolaser, followed by 12% C₃F₈ gas for intraocular tamponade. Six weeks post-operatively, his vision was 6/60 and the retina was attached with a 20% C₃F₈ residual gas fill. An abnormal foveal reflex was seen with a bubble visible at the fovea (Fig. 1). Based on clinical examination, previously published literature about various substances trapped subretinally during vitrectomy, and the surgery adjuncts, it was assumed that this bubble consisted of trapped PFCL. The infra-red image (Fig. 2a) demonstrated a very distinct hyporeflectant lesion at the fovea. A cross-sectional spectral domain-optical coherence tomography (SD-OCT) scan through the centre of this point revealed a full-thickness macular hole along with shadowing at the level of the choroid (Fig. 2b). This shadow is probably caused by side-scatter of the light when it meets the surface of a foreign body present anterior to the macular hole. While subretinal PFCL has a distinct appearance, this bubble was not subretinal, thus making the differentiation difficult between a gas bubble or PFCL trapped in the margin of a macular hole.

Six weeks later the remaining C₃F₈ in the vitreous cavity had disappeared, including the bubble at the posterior pole. Further SD-OCT imaging confirmed the absence of the hyporeflectant reflex at the fovea, allowing a normal choroidal appearance in the presence of the macular hole (Fig. 2c). At this time, complete fundus examination was possible, allowing examination of the inferior fundus for a displaced PFCL bubble. Such a finding was not observed, confirming that this initially clinically visible bubble could not have been PFCL. In addition to this, the patient did not report reappearing of the blurring in his vision when in a supine position. At this point, taking into consideration the substances used during surgery and the fact that the bubble was no longer present, it was concluded that it consisted of a C₃F₈ bubble. The patient subsequently underwent vitrectomy with internal limiting membrane peeling and injection of 12% C₃F₈ gas. Two weeks post-operatively, the macular hole was closed, and the patient’s vision improved to 6/24.

PFCL is widely used during complex retinal detachment repair associated with giant retinal tears, and retained PFCL is one of the most common complications of its use. When subfoveal PFCL is identified, surgical removal is recommended in view of its toxic effects on the retina [4]. OCT can be used for the imaging of the PFCL bubbles, demonstrating typical features such as retinal pigment epithelium disorganisation and disruption of the external limiting membrane [5].

Revising the published literature, there are reports of cases where other substances can be trapped subretinally during vitrectomy. Silicone oil particles resemble beads and are slightly mobile among subretinal strands by changing the eye position [6]. Triamcinolone granules gradually decrease over 2 weeks and resolve completely by 3 weeks, while on follow-up the retina appears successfully attached and no functional damage is observed, thus not necessitating any surgical intervention [7].

In our case the foveal bubble observed post-operatively was initially mistaken for retained subretinal PFCL. However, further careful examination together with SD-OCT imaging and along with the clinical progress of the finding clearly confirmed this was in fact a fragment of C₃F₈ lodged at the posterior pole.

Macular hole formation following retinal detachment surgery is not uncommon [8] and can be successfully closed following further surgery. In this case we do not believe the bubble of gas at the macula contributed to macular hole formation, given that there was no suspicion over expansion of the trapped gas bubble, for example due to changes of altitude or use of nitrogen monoxide during general anaesthesia. On the other hand, it is likely the macular hole allowed this phenomenon to become visible.

To our knowledge, this is the first described case of a retained fragment of fluorocarbon gas at the macula following successful retinal detachment repair and highlights a previously unreported cause of an abnormal foveal appearance. We believe the small bubble of gas became anchored in place by the edges of the macula hole, thus allowing the gas bubble to bridge over it. Clinical examination together with the use of SD-OCT is helpful in differentiating the appearance from that seen in retained PFCL, silicone oil, or triamcinolone.

Compliance with ethical standards.

The authors have no conflict of interest to declare. None of the authors has any proprietary interest related to this paper.

No grant support or research funding was received by any of the authors.