Jul 2016

with
Prof Charles McGhee
& A/Prof Dipika Patel
Series Editors
Intraocular foreign bodies.
What to do?
Fig 1. This patient developed endophthalmitis from an intraocular body that penetrated the
cornea, see sutured entry site. The IOFB in the photograph is secured in foreign body forceps
and about to be removed from the eye.
Fig 2. An IOFB lodged in the ciliary body has been detached from the surrounding tissue and is
about to be explanted from the eye.
BY ASSOCIATE PROFESSOR PHILIP POLKINGHORNE*
A
lot of the discourse on intraocular foreign bodies (IOFBs)
is concentrated on the morbidity associated with their
presence, timing of surgery and risk of endophthalmitis. All
important issues, but often neglected is the management of the
most common IOFB, the intraocular lens and or medical devices
that have become displaced and or adversely impacting on adjacent
structures. Such iatrogenic IOFBs by definition are much more
frequently encountered than those IOFBs from penetrating trauma.
In New Zealand we have relatively good statistics on ocular
trauma, because of ACC. On their website for the financial year
ending 2015, 30,000 ocular injuries were recorded. The website
does differentiate between types of injury, including foreign body
injuries (n=13,714) but the absolute numbers of intraocular foreign
bodies are not recorded. That data however can be extrapolated
from a recent survey performed in Waikato suggesting about 16
traumatic intraocular foreign bodies would be expected per year in
New Zealand. The authors of this paper also provide useful data on
the risks of infection associated with traumatic IOFBs (about 15%)
and the risk of evisceration (about 5%). 1
Overseas experience suggests infection is linked with delay in
presentation and when the foreign body is organic, particularly
when the object is wood and or contaminated with soil. Many
practitioners would advocate the prophylactic use of antibiotics and
tetanus toxoid in this scenario. In my own practice I tend not to use
prophylactic antibiotics for high velocity, metallic foreign bodies but
have a low threshold for organic IOFBs especially if a gas bubble is
seen in the eye.
The history is certainly important, not only to consider the
presence of an IOFB in an eye that has been traumatised, but to
provide an indication as to the type of foreign body. The ocular
examination may be difficult, especially in the presence of globe
rupture but in a closed globe setting a small corneal laceration, iris
defect and or sectorial lens opacity should suggest the presence of
an IOFB.
In figure 1 you can see that expert ultrasonography obviates the
need for other types of imaging, but most patients are aggrieved
if an IOFB is missed following trauma. Where there is doubt, a
plain X-ray will exclude larger metallic foreign bodies, but for
other IOFBs there is a risk of a false negative result. Many overseas
centres use CT scanning with 3 mm cuts to lessen this risk. MRI is
contra-indicated in the presence of metallic foreign bodies since the
electro-magnetic field can displace the IOFB, potentially damaging
adjacent intraocular structures but is useful in some instances of
non-metallic foreign bodies.
Of course not all IOFBs need to be removed and inert substances
such as plastics and glass fragments can be often left safely in the
eye. Many patients require reassurance if that advice is given. I find
a second opinion from another colleague is useful in that scenario.
If removal of the IOFB is indicated, I prefer, as a rule to defer
surgery for a week or two, to enable a posterior vitreous separation
to occur. Nearly all patients share the demographic of being male
and aged under 30 years, so if the foreign body is small and the
wound self-sealing I think it is better to wait for the vitreous
separation. The exception to this policy is where there is a suspicion
of contamination. Prompt vitrectomy and intra-vitreal antibiotics
is mandatory in that circumstance. The presence of an IOFB in an
eye with an open globe injury is an absolute indication for acute,
primary closure but again I would tend to defer removal of the
foreign body for a week or so.
I don’t think the location influences the timing of the surgery.
In my hands IOFBs in the ciliary body or ora are more difficult to
remove than those behind the equator. Sometimes the lens may
have to be sacrificed in anteriorly located IOFBs. One recent case
required three surgeries to locate the IOFB within the ciliary body.
(See figure 2). Persistence was required in that case because of the
risk of siderosis.
All posterior segment IOFBs require a vitrectomy. If there are
media opacities such as cornea scars and/or cataract, combined
surgery may be needed. I find it very helpful to engage an anterior
segment specialist if a temporary kerato-prosthesis is likely to be
needed during the proposed surgery. Their skill in facilitating a
closed environment is vastly superior to any open-sky technique
of old. Conversely, combining cataract vitrectomy surgery usually
requires only one operator.
IOFBs embedded in the retina or choroid requires careful
dissection, good haemostasis and tamponade with gas or oil
is often essential. (See figure 3). Of course not all IOFBs need
to be removed and inert substances such as plastics and glass
fragments can be often left safely in the eye. Many patients require
reassurance if that advice is given. I find a second opinion from a
colleague is useful in that scenario.
As a rule, stable intraocular lenses are not normally a hindrance
to removing an IOFB and similarly a clear crystalline lens can be
left in situ. I place more importance on removing as much vitreous
as possible to safely remove the IOFB but try not to overstep the
mark with a zealous approach to the vitreous. Many IOFBs are
encapsulated at the time of surgery and some dissection is usually
required. This can be achieved with a MVR blade or 25-gauge needle
on a 1 or 3 ml syringe. The capsule is dissected sufficient to free
the IOFB, or at least mobilise. As for the forceps I use the smallest
that will safely lift the foreign body and guide it through the
sclerotomy. The later generally needs to be enlarged, as a rule twice
the size you initially calculate. I generally find magnetic probes (rare
earth magnets) are not sufficient to retain contact through the
sclerotomy.
Very large IOFBs, (greater than 10 mm), may have to be removed
through the anterior segment, although this depends on the width
of the foreign body.
Dislocated intraocular lenses, and other therapeutic devices such
as capsular tension rings should be removed when dislocated, but
optical considerations outweigh any perceived risk to the retina.
The intraocular lens may be able to be correctly relocated into the
pupillary aperture and stabilised, usually by means of a prolene
suture but this does require a haptic profile that lends to that
approach. There is a wide range of capsular tension rings that have
been inserted in the last decade; some eyes have more than one
device. Removal requires a dialing action not only to free from an
intraocular attachment in or about the pupillary plane but also
from the anterior segment. That approach will limit the size of the
ab externo incision.
The upsurge in the use of selective corneal tissue, particularly
endothelial grafting has created a new, albeit very rare complication
where the tissue can become dislodged and settle on another
intraocular structure. If this tissue enters the posterior segment
then removal and relocation should be performed as soon as
possible, before the cornea becomes oedematous and the view
difficult. (See figure 4). Furthermore if the tissue is rapidly relocated
then it should continue to act as originally intended.
In summary iatrogenic IOFBs are more numerous than those
resulting from traumatic causes but the later have the propensity to
cause more medico-legal problems. ▀
References
1. Pandita A, Merriman M. Ocular Trauma Epidemiology: 10-year retrospective
study. NZ Med J. 2012: 125;61-69.
About the author
* Philip Polkinghorne is a vitreo-retinal surgeon in
Auckland, expert diver and fisherman.
Fig 3. Fundal photograph demonstrating an IOFB penetrating the retina near the macula.
Fig 4. Corneal Donor Tissue (comprising of a thin layer of corneal stroma, Descemets
membrane and corneal endothelium) on surface of the retina. This was subsequently
elevated and re-attached to the cornea.
July 2016
NEW ZEALAND OPTICS
17