Late-Onset Subretinal Silicone Oil Migration through Optic Disc Coloboma Open Access

Introduction: This report describes a case of late onset subretinal silicone oil migration in an eye with congenital optic disc coloboma and its treatment. Case Presentation: A 15-year-old male with a history of left eye congenital optic disc coloboma and amblyopia presented with a third recurrence of retinal detachment (RD) with proliferative vitreoretinopathy. The patient underwent PPV, subretinal fluid drainage through a peripheral retinotomy, silicone oil tamponade, and endolaser around the coloboma and retinotomy. The retina re-attached successfully. However, 14 months postoperatively examination revealed high intraocular pressure (IOP) of 33 mm Hg and a sub-macular bubble of silicone oil was evident. The patient underwent sub-macular silicone oil removal. Conclusion: Here we describe the unique late-onset subretinal migration of intravitreal silicone oil following RD repair in an eye with optic disc coloboma in association with raised IOP. This case demonstrates potential mechanisms of subretinal silicone oil migration through the coloboma that serves as a passage and an increased IOP, which drives the oil from the vitreous to the subretinal space.

Congenital optic disc colobomas have a high incidence of retinal detachments (RDs) [1]. Subretinal silicone oil migration has been previously reported in eyes with disc coloboma [2].

Importantly, subretinal migration of silicon oil is usually encountered in the early postoperative period. Silicone oil in the presence of optic disc pit may have serious complications requiring clinician awareness, including retrolaminar and intraventricular migration with potential vision loss and central nervous system toxicity.

We report a unique case of late subretinal migration of silicone oil accompanied by increased intraocular pressure (IOP) following repair of RD in an eye with congenital optic disc coloboma. This case demonstrates a potential pathogenesis for subretinal silicone oil migration through the coloboma. The CARE Checklist has been completed by the authors for this case report, attached as online supplementary Material 1 (for all online suppl. material, see https://doi.org/10.1159/000545661).

A 15-year-old male with a history of left eye congenital optic disc coloboma and amblyopia presented for second opinion due to a third recurrence of RD. Two months earlier, he had a left RD and was treated with left eye scleral buckle, lensectomy, intraocular lens implantation, and pars-plana vitrectomy (PPV) with gas tamponade. One month prior to presentation, he had a recurrent RD that was treated with PPV and silicone oil tamponade. The patient presented complaining of reduced vision in his left eye.

Examination of the left eye revealed best-corrected visual acuity (BCVA) of finger counting from 3 m, IOP of 14 mm Hg, a clear cornea, a deep anterior chamber, and an intraocular lens located in the capsular bag. The posterior segment examination showed silicone oil filling the vitreous cavity, optic disc coloboma, macula off inferior RD, scleral buckle indentation 360°, and peripheral proliferative vitreoretinopathy (PVR) with epiretinal membranes. The right eye had a BCVA of 6/6, IOP of 14 mm Hg, and a normal anterior and posterior segment.

The patient underwent PPV, removal of SO, peeling of PVR membranes, drainage of subretinal fluid through a peripheral inferotemporal retinotomy, use of perflourodekalin heavy fluid, endolaser around the coloboma, and high-density silicone oil tamponade. During the first four postoperative months, the patient was treated with 8 intravitreal methotrexate injections for prevention of PVR. During the follow-up treatment with timolol, brimonidine and dorzolamide twice daily was administered due to elevated IOP. Ten months following surgery, the patient reported improved vision in the left eye, BCVA was 6/60, IOP 22 mm Hg, and a flat retina under silicone oil (SD-OCT in Fig. 1a).

On routine examination 14 months following the last surgery, the left eye BCVA was 0.1, IOP 33 mm Hg, flat retina, a sub-macular silicone oil bubble was seen evident on OCT as hypo-reflective subretinal roundish spaces; there was no connection between the sub-macular SO bubble and the optic disc coloboma and the retina was totally flat (Fig. 1b). One month later, the patient underwent vitrectomy with silicone oil removal. An attempt to aspirate the sub-macular silicone oil with a 38G silicone tip cannula failed. So, perfluorodekalin heavy fluid was injected above the macula to push on the sub-macular silicone oil bubble, which was then aspirated with 38G canula successfully. Upon follow-up 3 weeks after surgery, BCVA was FC2.5M, IOP 14 mm Hg. The retina was flat (Fig. 2). SD-OCT of the left eye 3 weeks following silicon oil removal and drainage of subretinal silicone oil demonstrated decreased subretinal silicone oil, with a clearance of the sub-foveal silicone oil bubble (Fig. 1d). There was a central foveal atrophy with ellipsoid zone disturbance, which was present previously.

To the best of our knowledge, the present case is the first to describe a late onset of subretinal silicone oil migration following RD repair in congenital optic disc coloboma. Optic disc colobomas are usually located inferonasally. The condition is thought to result from incomplete closure of the embryonic ocular fissure in utero; family history is usually negative. A high risk of RD, nearly 40%, exists in those eyes. The pathogenesis of RD is presumed to involve defects in the locus minoris resistentiae, premature vitreous liquefaction, and thin rudimentary retina with breaks in the area of the coloboma [1, 3, 4].

Repair of disc coloboma-associated RD with PPV and long-acting tamponade by silicone oil provides better outcomes, compared with scleral buckle [1, 5]. Subretinal migration of silicon oil has been described in optic nerve colobomas and pits, even in the absence of retinal breaks. The migration is usually evident early following intravitreal silicone oil injection and most probably occur at the time of surgery, the most probable route being the locus minoris resistentiae in the coloboma. Intraocular and cerebrospinal fluid pressure gradient is also thought to play a significant role in the movement of silicone oil from the vitreous cavity through the coloboma defect to the subretinal or retrolaminar spaces. In support of this, the late presentation in our patient occurred only following a rise in IOP [2].

Subretinal silicone oil may lead to vision loss caused by RD or toxicity due to chronic inflammation with giant cell infiltration of retinal tissue proximal to silicon oil droplets [6]. Therefore, awareness and prompt recognition are vital; OCT may aid in detection of this complication. This case is unique for its rare late presentation and contribution to the understanding of subretinal migration of silicon oil in optic disc colobomas. The main limitation associated with our case is the rarity of the condition; additional cases of late silicon oil migration in optic disc coloboma may enhance the knowledge of this uncommon complication.

Late-onset subretinal migration of intravitreal silicone oil may occur following RD repair in eyes with optic disc coloboma and may result from or be aggravated by raised IOP. Subretinal silicone oil may have serious complications, thus emphasizing the need for clinician awareness and early recognition. This case also implies potential mechanisms of subretinal silicone oil migration including the coloboma that serves as a passage and an increased IOP, which drives the oil from the vitreous to the subretinal space. Also, we describe here the removal of sub-macular silicon oil through small gauge cannula, which can be assisted with injection of perfluorocarbon heavy fluid, which helps push on the bubble.

I am happy with the treatment I received. I am aware of the potential risks of subretinal silicone oil migration, and I encourage doctors to identify this condition.

This case report was conducted in compliance with local guidelines; thus, ethical approval was not required. All procedures adhered to ethical requirements outlined in the Helsinki Declaration. The analysis contains no identifying information from the patient. Written informed consent was obtained from the parent of the patient for publication of the details of their medical case and any accompanying images.

All authors declare no conflict of interest.

This research did not receive any specific funding.

Conceptualization and supervision: T.J.; methodology, formal analysis, and investigation: T.J. and O.S.; and writing – original draft preparation and preparation of figures: O.S.

This article includes all data analyzed in this study, and further inquiries can be directed to the corresponding author.