Abstract
BackgroundTo evaluate ocular fluid filtration and endplate positioning in glaucomatous eyes with long-tube glaucoma drainage devices (GDDs) using magnetic resonance imaging (MRI) and the effects of various factors on postoperative intraocular pressure (IOP).MethodsThis observational case series included 27 consecutive glaucomatous eyes (18 men, 7 women; mean age ± standard error, 63.0±2.0 years) who underwent GDD implantation (n = 8 Ahmed Glaucoma Valves [AGV] and n = 19 Baerveldt Glaucoma Implants [BGI]). Tubes were inserted into the pars plana in 23 eyes and anterior chamber in 4 eyes. Six months postoperatively, high-resolution orbital images were obtained using 3-Tesla MRI with head-array coils, and the filtering bleb volume, bleb height, and distances between the anterior endplate edge and corneal center or limbus or between the endplate and orbital wall were measured.ResultsIn MR images obtained by three-dimensional fast imaging employing steady-state acquisition (3D-FIESTA) sequences, the shunt endplate was identified as low-intensity signal, and the filtering bleb was identified as high-intensity signals above and below the endplate in all eyes. The 6-month-postoperative IOP level was correlated negatively with bleb volume (r = -0.4510, P = 0.0182) and bleb height (r = -0.3954, P = 0.0412). The postoperative IOP was significantly (P = 0.0026) lower in BGI-implanted eyes (12.2±0.7 mmHg) than AGV-implanted eyes (16.7±1.2 mmHg); bleb volume was significantly (P = 0.0093) larger in BGI-implanted eyes (478.8±84.2 mm3) than AGV-implanted eyes (161.1±52.3 mm3). Other parameters did not differ.ConclusionsThe presence of intraorbital/periocular accumulation of ocular fluid affects postoperative IOP levels in eyes implanted with long-tube GDDs. Larger filtering blebs after BGI than AGI implantations explain lower postoperative IOP levels achieved with BGI than AGV. The findings will contribute to better understanding of IOP reducing mechanism of long-tube GDDs.
Highlights
Glaucoma is a chronic disease characterized by progressive loss of the retinal nerve fiber layer and associated visual field loss [1,2], and the intraocular pressure (IOP) is currently the only modifiable risk factor [3]
IOP levels in eyes implanted with long-tube glaucoma drainage devices (GDDs)
The findings will contribute to better understanding of IOP reducing mechanism of long-tube GDDs
Summary
Glaucoma is a chronic disease characterized by progressive loss of the retinal nerve fiber layer and associated visual field loss [1,2], and the intraocular pressure (IOP) is currently the only modifiable risk factor [3]. Implantation of glaucoma drainage devices (GDDs) made of different materials are being used increasingly to treat early and advanced glaucoma worldwide [6,7] and more recently in Japan [8,9,10]. Among the various types of GDDs, the device with an endplate and long tube has been successfully used in complicated glaucoma cases, including neovascular glaucoma, aphakic and pseudophakic glaucoma, postpenetrating keratoplasty glaucoma, pediatric glaucoma, and uveitic glaucoma [11,12,13,14]. The long-tube types of GDDs currently used often include the Ahmed Glaucoma Valve (AGV) (New World Medical, Rancho Cucamonga, CA), the Baerveldt glaucoma implant (BGI) (Abbott Medical Optics, Abbott Park, IL), and the Molteno Implant (Molteno Ophthalmic, Dunedin, New Zealand) [6]. Resonance Imaging in Eyes Implanted with LongTube Glaucoma Drainage Devices.
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