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Several long term complications have been reported with MAI scleral buckles,1–3 a synthetic hydrophilic scleral buckling element, first introduced in the 1970s.1 We present a case of an extruding, hydrated MAI scleral buckle that presented as an orbital lesion. The magnetic resonance imaging (MRI) characteristics of the hydrated MAI buckle are also described.
An 81 year old woman was referred to the orbital service for evaluation of a freely mobile non-painful subconjunctival lesion in the left eye present for at least a year. The extraocular movement was full but with a small left exotropia in primary gaze. Anterior segment examination revealed a firm, nodular subconjunctival lesion in the superomedial quadrant. The diagnosis of extruding scleral buckle versus a large orbital conjunctival inclusion cyst was entertained. She, however, denied a history of retinal detachment repair.
The patient underwent MRI of the orbits with and without gadolinium infusion which revealed a 2.5×0.7 cm2 elongated, elliptical mass in the medial intraconal space. The hyperintensity of the mass on T2 weighted images, indicative of high water content, led to the mistaken radiological diagnosis of a cystic, fluid filled lesion (fig 1). Introperatively, a swollen intact segmental buckle was encountered that disintegrated into small and large pieces when grasped with a forceps. Complete meticulous removal of these small fragments was performed (fig 2).
MAI hydrogel explant is made of polymethyl acrylate-co-2-hydroxyethyl acrylate crossed linked with ethylene diacrylate with 15% water2 and was considered an ideal scleral buckling material since it was as effective as solid silicone rubber buckle and sponge but with lower incidence of erosion.4 However, long term complications are being more frequently recognised with the MAI buckle.3 Complications include hydration of the buckle with erosion and extrusion of the explant.2 Owing to their hydrophilic nature, buckles tend to swell, become bulky, and displace from their intended position. These explants change from an opaque, soft, spongy, whitish appearance to a translucent, gel-like, cream coloured material with hydration.2 They become extremely friable and fragment easily with slight traction upon removal.1–3 Scanning electron microscopy of these hydrated buckles has revealed distortion of their micropore architecture.1,2
The presentations of hydrated MAI buckles are varied. They can become extremely loose and migrate anteriorly, or enlarge in situ and present as orbital masses. Since complications do not occur until many years after the orbital surgery, the history of a retinal detachment repair may not be elicited. In addition, these loose buckles usually do not indent the globe and may not be recognised as being present on indirect ophthalmoscopy.
Radiological imaging may be helpful. MRI T1 weighted images of a hydrated buckle reveal a well defined, hypointense mass, while T2 weighted images reveal a hyperintense mass as a result of high water content. (In contrast, a silicone element will be black on MRI images.)
Removal of hydrated MAI buckles can be very difficult. Careful sub-Tenon dissection should be carried out since any pressure on the buckle can lead to its fragmentation. The procedure is often complicated because of the extremely friable nature of these buckles. Cryoprobe has been used successfully in some cases for removal of the buckles.5 Le Rouic et al demonstrated that removal of MAI buckles with a cryoprobe is a safe and effective technique with lower fragmentation rate compared to the use of forceps.5 The cryoprobe allows the water in the swollen explant material to freeze, which helps to reduce fragmentation.
In conclusion, ophthalmologists should be aware of the possible complications of the MAI hydrogel buckles. Knowledge of the MRI characteristics of hydrated MAI buckles may be helpful in identifying them in the event they present as a space occupying orbital mass.
Supported by an unrestricted grant from Research to Prevent Blindness.
Competing interests: none declared
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