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.
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.
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.
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.1- 5
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
Corresponding author: Helen V. Danesh-Meyer, MD, FRACO, Department
of Ophthalmology, University of Auckland, Auckland, New Zealand (e-mail: email@example.com).
Danesh-Meyer HV, Spaeth GL, Maus M. Cosmetically Significant Proptosis Following a Tube Shunt Procedure. Arch Ophthalmol. 2002;120(6):846-847. doi: