title: Ahmed glaucoma valve implants in the pediatric population: the use of magnetic resonance imaging findings for surgical approach to reoperation.
abstract: OBJECTIVE
  To describe and to evaluate a novel application of magnetic resonance imaging (MRI) in determining the Ahmed glaucoma valve (AGV) function after implantation.
  
  
  METHODS
  Retrospective interventional case series of all surgical glaucoma patients in one practice were identified and orbital MRI series were performed. Orbital MRI findings were evaluated in all children who had undergone Ahmed glaucoma valve insertion.
  
  
  RESULTS
  A total of six patients were identified, ranging in age from 1 to 14 years. Mean follow-up time ranged from 1 to 3 years from the time of first tube insertion. Gadolinium enhancement MRIs showed an enhanced large cystic cavity over the plate in five patients, indicating partial to complete patency of the outflow of the tube. One MRI failed to show an enlarged enhanced bleb over the plate region, indicating potential obstruction of outflow. Surgical irrigation of the tube displayed obstruction. Ahmed tube exchange was performed. Enhanced cystic bleb showed compression of the extraocular muscles in four patients. These patients exhibited mild to moderate restrictive strabismus. No lenticular opacification was noted in the four phakic patients.
  
  
  CONCLUSIONS
  Early and late AGV failure and subsequent intraocular pressure rise are of great concern after pediatric glaucoma shunt surgery. Orbital MRI series should be considered in the cases of possible AGV drainage failure. In cases of reoperation, orbital MRI findings could be of great clinical value to evaluate for functional patency as well as for the EOM surgical intervention approach. To avoid unnecessary surgical exploration/explantation, orbital MRIs with gadolinium-dye enhancement should be considered in evaluating postshunt glaucoma surgical patients.
authors.affiliation: Division of Ophthalmology, San Diego Children's Hospital, and Department of Pediatrics, University of California-San Diego, 3030 Children's Way, San Diego, CA 92123, USA. amirpirouzian@msn.com
authors.forename: Amir
authors.initials: A
authors.lastname: Pirouzian
authors.forename: Colin
authors.initials: C
authors.lastname: Scher
authors.forename: Henry
authors.initials: H
authors.lastname: O'Halloran
authors.forename: Yvette
authors.initials: Y
authors.lastname: Jockin
mesh_terms: D000293:Adolescent; D001082:Aqueous Humor / Q000378:metabolism; D002648:Child; D002675:Child, Preschool; D005260:Female; D005901:Glaucoma / Q000175:diagnosis* / Q000601:surgery*; D020327:Glaucoma Drainage Implants; D006801:Humans; D007429:Intraocular Pressure; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D009915:Orbit / Q000473:pathology*; D011475:Prosthesis Failure; D019919:Prosthesis Implantation