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Glaucoma drainage devices are commonly used nowadays in cases of secondary glaucoma, especially silicone oil (SO) glaucoma. Even after removal of SO from the vitreous and anterior chamber, due to remnant droplets in the drainage tube, intractable glaucoma can occur. We hereby report one such case.
A 28-year-old man, known case of Marfan syndrome, presented with secondary glaucoma in left eye (OS) following multiple vitreo-retinal surgery after rhegmatogenous retinal detachment 1 year ago (5000 cs SO in situ). Six months after last vitreoretinal surgery, complete SO removal was performed owing to high intraocular pressure (IOP), however subsequent follow-up visits showed persistently high IOP, for which he underwent placement of a non-valved glaucoma drainage device (GDD) (Aurolab aqueous drainage implant (AADI), Aurolabs, Madurai, India). AADI was placed in the superotemporal quadrant, as areas of significant scleral thinning were identified in the inferonasal quadrant. The tube length however was longer than usual, measuring 3 mm in anterior chamber. At 1 month follow-up visit, the tube orientation shifted more horizontally further increasing the tube length and the patient developed high IOP OS which was managed by topical timolol maleate 0.5% and dorzolamide 2%. After 2 months, the IOP OS was 32 mm Hg. Slit lamp and gonioscopic evaluation OS revealed bubbles of SO blocking the AADI tube and obscuring the view of the tube ostium (figure 1A,B). High IOP persisted refractory to ocular hypotensive medications, making the eye symptomatic, for which G6 Micropulse diode laser treatment (IRIDEX Cyclo G6 1500 mW power and 180 s with 31.3% duty cycle) was performed.
Incidence of glaucoma after SO injection ranges from 4.8% and 48%, and emulsification of oil is a major contributor towards the same.1 Emulsification involves failure of dispersed oil bubbles to reform into a single large globule and can occur anywhere between 5 and 24 months (mean of 13.2 months) after injection.1 This depends on multiple factors, including the purity and viscosity of the oil, fibrinogen, serum, fibrin, blood low density lipoproteins, surfactants on surgical instruments and sterilisation agents. Extravasation of intraocular emulsified oil into the subconjunctival space through sclerotomy and valved GDD has been previously published in literature.2–5 However, the same through non-valved devices has not been extensively documented.6 7 We report this to emphasise that elevated IOP can occur even after SO removal due to obstruction of a non-valved glaucoma drainage tube by smaller SO droplets. Some modifications which have been proposed to prevent or prolong the development of this extraocular oil migration through tube are usage of a shorter tube in anterior chamber, pars plana insertion of the drainage tube into the vitreous, placing of tube shunt in the inferonasal quadrant.6 7 High molecular weight and high viscosity SO (5000 cs) is more resistant to dispersion and emulsification and may be preferred, however it is important to remember that even these oils can lead to drainage tube blockage and cause intractable glaucoma, as seen in our patient.6
Understanding the forces and factors that lead to silicone oil (SO) emulsification is crucial in minimising its occurrence.
It is always recommended to remove SO within 1 year postoperative, unless there is a risk of redetachment, and even if the oil is completely removed before placement of a glaucoma drainage device, residual SO bubbles may still block it.
Prevention of this complication includes placement of a short tube well anterior to the iris in the inferior portion of the anterior chamber.
Contributors SR: idea, data collection, writing, proofing. VAS: idea, data collection, writing, proofing. SS: writing, proofing.
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Competing interests None declared.
Patient consent for publication Obtained.
Provenance and peer review Not commissioned; externally peer reviewed.
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