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Clinicopathologic Reports, Case Reports, and Small Case Series
June 2002

Cosmetically Significant Proptosis Following a Tube Shunt Procedure

Arch Ophthalmol. 2002;120(6):846-847. doi:

A 16-year-old boy was hit in the right eye with a paint ball, resulting in a dislocated lens, prolapsed iris, and a vitreous hemorrhage. He had a lensectomy, vitrectomy, and complete iridectomy. subsequent visual acuity was hand movements OD and a right afferent pupillary defect with no identifiable anterior segment structures. The visual acuity in was 20/20 OS. One month following surgery, the patient developed elevated intraocular pressure (IOP) ranging between 40 and 50 mm Hg. The patient was referred for management of his glaucoma.

Report of a Case

When we first saw the patient, the optic disc of the right eye had a cup-disc ratio of 0.6. In contrast, the left optic disc had almost no cup. It was believed that marked glaucoma damage had already occurred. Visual acuity was too poor to permit a meaningful visual field examination. It was believed that surgery was necessary to control the IOP, and because of the extensive scarring caused by the previous surgery and the absence of vitreous, a tube shunt procedure was considered appropriate.

An Ahmed (New World Medical Inc, Cucamonga, Calif) tube shunt with a Tutoplast (Tutogen Medical Inc, Clifton, NJ) patch graft was implanted superotemporally without complication, and the tube was placed into the anterior chamber. The IOP postoperatively was consistently lower than 21 mm Hg. However, there was gradually increasing proptosis, and by 2 months postoperatively, he had developed 6 mm of proptosis, with marked displacement of the right globe inferiorly. There was significant limitation of elevation, restriction of abduction, and exposure keratitis of the right eye. The patient and his parents were notably unhappy with the cosmetic result. Magnetic resonance imaging results revealed a large, focal collection of fluid superolaterally to the globe. The tube shunt could be identified within the fluid collection (Figure 1). The diagnosis was proptosis caused by the cyst surrounding the Ahmed tube shunt.

figure
Magnetic resonance imaging shows the tube shunt within a collection
of fluid superolaterally to the globe.

Magnetic resonance imaging shows the tube shunt within a collection of fluid superolaterally to the globe.

It was elected to follow up the patient conservatively. The exposure keratitis was treated with intensive lubrication and it gradually cleared. The IOP remained between 12 and 15 mm Hg. There was no symptomatic diplopia, presumably because of the poor vision in the right eye. After 6 weeks of follow-up, the proptosis had decreased to a 1-mm difference between the 2 globes and there continued to be mild limitation of elevation of the right eye. One year later, the eye remained slightly proptosed and inferiorly displaced, but the cosmetic defect was considered tolerable by the patient and his parents.

Comment

To our knowledge, this is the first reported case of proptosis following implantation of a drainage device. Oculomotility problems secondary to tube shunts are known complications of Ahmed, Krupin (Hood Laboratories, St Pembroke, Mass), Baerveldt (Pharmacia & Upjohn, Bridgewater, NJ), and Molteno (OP Inc, Costa Mesa, Calif) drainage implants.15 There has been 1 reported case of extraocular muscle restriction with the Ahmed tube shunt. The tube shunt was placed superonasally and resulted in an acquired pseudo-Brown syndrome on the first postoperative day.

Oculomotility disturbances may result from several factors. First, when an implant placed under the rectus muscles is responsible for producing diplopia, the limitation of movement is in the direction of the implant, eg, a superotemporal quadrant implant produces a hypotropia that increases in upgaze, an esotropia that increases in abduction, or a combination of both. This is thought to be related to a posterior fixation effect induced by scarring between the muscle belly and the sclera. Scarring posterior to the widest portion of the implant will weaken the function of the muscle in its field of action. Second, a large bleb produced by aqueous expansion of the capsule that forms around the reservoir may result in a crowding-effect that limits the movement of the eye and in mechanical displacement of muscles.3 The most common factor that results in oculomotility disturbances is the large size of the implant and its location or extension under a muscle belly. Many patients with motility disturbance secondary to drainage device placement require surgical intervention to correct the misalignment. In our case, the proptosis and motility disturbance appeared 2 months after the placement of the Ahmed device and resolved partially 6 weeks following the initial visit.

This case highlights the motility disturbance that may be a complication of drainage devices, emphasizing the need for an appropriate discussion with the patient prior to surgery. It also reports, to our knowledge, the first case of proptosis following the placement of an Ahmed tube shunt. Finally, it suggests that a period of observation may be useful before embarking on surgical correction for motility disturbances following implantation of drainage devices.

Corresponding author: Helen V. Danesh-Meyer, MD, FRACO, Department of Ophthalmology, University of Auckland, Auckland, New Zealand (e-mail: h.daneshmeyer@auckland.ac.nz).

References
1.
Topouzis  FColeman  ALChoplin  N  et al.  Follow-up of the original cohort with the Ahmed glaucoma valve implant. Am J Ophthalmol. 1999;128198- 204Article
2.
Huang  MCNetland  PAColeman  AL  et al.  Intermediate-term clinical experience with the Ahmed glaucoma valve implant. Am J Ophthalmol. 1999;12727- 33Article
3.
Ball  SFEllis  GSHarrington  RG  et al.  Brown's superior oblique tendon syndrome after Baerveldt glaucoma implant [letter]. Arch Ophthalmol. 1992;1101368Article
4.
Coats  DKPaysse  EAOrenga-Nania  S Acquired pseudo-Brown's syndrome immediately following Ahmed valve glaucoma implant. Ophthalmic Surg Lasers. 1999;30396- 397
5.
Christmann  LMWilson  ME Motility disturbances after Molteno implants. J Pediatr Ophthalmol Strabismus. 1992;2944- 48
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