Intraocular Foreign Bodies - Management
INTRAOCULAR FOREIGN BODIES - MANAGEMENT
Jay Chhablani MD
Intraocular foreign body (IOFB) injuries vary in presentation, outcome, and prognosis depending upon various factors. Increased awareness about eye protection, improved surgical techniques, and advancements in bioengineering are responsible for an improved outcome in injuries with IOFB . The limiting factor is still the extent of the initial injury.
PATHOPHYSIOLOGY: The location and damage caused by an IOFB will depends on several factors including the size, shape, and composition of the object as well as the momentum of the object at time of impact. Usually an IOFB causes less acute damage in comparison to blunt trauma, however, large irregular IOFBs may cause significant initial damage. Subsequent damage depends on the content of the IOFB. Inert substances such as glass, stone, and plastic are better tolerated than metals that oxidize such as copper or iron. Metallic and magnetic IOFBs are the most common. Organic material such as vegetable matter, cilia causes severe tissue reaction and may lead to endophthalmitis.
FREQUENCY: Of the penetrating injuries, 18-40% have at least one IOFB. Most common age group affected by IOFB injuries is middle age (20-40 years). Most injuries occur at work using various tools with metal striking metal such as hammer and chisel.
The history is a very important aspect of IOFB injuries with respect to finding a clue about the nature of the IOFB, for medical-legal aspects, and possibly for workman compensation. Patient may give a vague description of the accident, but this can still give a clue about the nature of injury. Patients frequently feel something entering the eye with no obvious external changes; hence, the incident usually is dismissed quickly. Sometimes patients may not complain of vision loss or severe pain, but a small entry wound can be found on careful examination. Determining the nature and size of IOFB is very important for planning the management. Explosives and firearms usually cause binocular damage with multiple foreign bodies, which are usually a combination of copper and lead.
A complete examination of both eyes is necessary, even if the other eye is apparently not involved or asymptomatic. The detailed examination of the eye and the adnexa is mandatory in case of IOFB injuries. Careful examination of eyebrows/lids for any lacerations/small foreign bodies is must. Slit lamp examination usually is able to locate an IOFB in the anterior segment. A scleral entry site may be seen with an area of conjunctival injection with or with conjunctival tear. Pigment over the scleral entry site may suggest uveal tissue prolapse. Entry sites in the cornea may be seen as a disruption in the smooth surface with corneal edema surrounding the entry site. It is not uncommon to have a negative Seidel’s test as there could be a self sealed wound. Examining the iris using retroillumination may reveal a disruption site (Iris Hole),and this may be the only sign of perforating injury. Using the entry point either at the cornea or sclera and the disruption point of the iris may help in localizing the IOFB by creating a trajectory path. Close examination of the natural lens specially the lens periphery is needed to decide the surgical management. It is best to examine the iris before dilatation and the lens after dilatation. Pupillary examination may reveal afferent pupillary defect or anisocoria. Gonioscopy is valuable to visualize the angles if suspicion exists about an IOFB in the angle. Gonioscopy should be performed carefully to avoid any tissue prolapse. Dilated fundus examination usually reveals the IOFB when it is in the posterior segment. Fundus examination could be difficult if hyphema / vitreous hemorrhage occurs. Scleral depression generally is not recommended when an IOFB is suspected and the wounds are not self-sealing. However, peripheral examination should be done to the extent possible to look for the IOFB.
LOCALIZATION AND CONFIRMATION OF DIAGNOSIS :
Localization of the IOFB is the prime aspect of management. The first question to answer is whether the IOFB is in the eye or in the orbit. Before the development of CT scans, a standard X-ray was used for localization. Plain X-ray is useful in radio-opaque foreign bodies only and will not detect radiolucent IOFBs such as wood or glass The standard “foreign body x-ray series,” includes Water’s, Caldwell, and lateral views. Plain x-ray films, with Caldwell or Water’s projections, may demonstrate the presence, but not the location of the IOFB.
The Sweet localization technique involves frontal and lateral projections. A foreign body within the globe can be localized with a bone-free examination by eye movement. This study localizes the foreign body to either the anterior or the posterior segment of the eye. In case of a foreign body in the anterior segment, the object will rotate in the same direction as the eye. The object will move in a opposite direction opposite to the eye movement if its location is in the posterior segment.
Localization using METAL LOCATORS either placed on the eye with a contact lens or sutured to limbus may also be done. This may help by localizing the foreign body either to the anterior or the posterior segment of the eye. The various metal locators are Berman, Roper-Hall, and Bronson-Turner.
Computed tomography provides much more reliable information regarding the size, shape, and localization of the foreign body. MRI generally is not used in metallic IOFB. MRI may be more effective in localizing nonmetallic IOFB such as wood. Ultrasound can be a useful adjunct in localizing IOFB and to determine if the object is metallic. Ultrasound could be performed carefully in case of an open globe injury. Ultrasonography is useful in determining the extent of the intraocular damage, determining the presence of a retinal detachment,double perforation, as well as in detecting foreign bodies not seen on x-ray studies. Ultrasonography can give an idea about the nature of the IOFB such as round or spherical foreign bodies, intraocular air, glass etc. Ultrasound biomicroscopy is needed if FB in the angle is suspected.
TREATMENT: Treatment of the injured eye with an IOFB includes protection of the globe with a shield, avoiding any pressure over the globe. Tetanus coverage should be checked. Cleaning up the surrounding area and removing small pieces of foreign bodies around the eye should be done, especially in cases of explosives. A delay in management may be complicated by infections. Broad-spectrum antibiotic prophylaxis should be started. Vegetable matter poses high risks for endophthalmitis so, should be removed urgently. Substances with inert properties may be removed at a later time after the initial wound is closed. The definitive management is surgical. During surgery, the conjunctival opening should be carefully done, taking care to remove superficial foreign bodies and to avoid any damage to prolapsed uveal tissue.
If the IOFB needs to be removed it is necessary to determine if it is anterior or posterior to the iris because the surgical approach will vary.
ANTERIOR INTRAOCULAR FOREIGN BODY (WHEN IOFB IS ANTERIOR TO THE IRIS PLANE)
No lens involvement:
If the lens is not involved, pupil should not be dilated or constricted by miotics to prevent any further injury to the lens. A careful examination to look for the entry wound should be performed and if needed, the suspected wound can be explored. Any wound that is not self-sealing is closed using the suture of choice for the specific tissue. Reforming and maintaining the anterior chamber (AC) depth is of utmost importance prior to removing the IOFB. Usually an injection of balanced salt solution or a viscoelastic through the paracentesis port is recommended. Even self-sealed entry wounds can re-open while forming the anterior chamber, so careful manipulation is suggested. Injection through the entry site should not be done. Viscoelastics are preferred for their ability to better maintain AC depth and protect the corneal endothelium. It is important to remove any residual viscoelastic at the end of surgery to reduce the risk of intraocular pressure rise. Removal of the IOFB is not recommended through the original entry wound. The foreign body should be removed through a surgical incision depending on the location and size of the foreign body. Usually a shelved incision of a size as large as the IOFB either in clear cornea or sclera is created. A 20-gauge rare earth magnet may retrieve the object through the surgical incision if it is metallic and small. Nonmagnetic objects or large magnetic objects are best managed with intraocular forceps. Care should be taken while removing the foreign bodies to avoid any injury to surrounding tissue. Samples of any anterior chamber aspirate maybe sent for microbiological evaluation if signs of infection are present or infection is suspected. With lens involvement : If the IOFB has damaged the lens, the lens should be removed. Generally, patients are young with a soft nucleus, which enables easy phacoemulsification or a manual extracapsular cataract extraction (ECCE) may be performed. Lensectomy could be an option in case of subluxation of the injured lens. Concurrent intraocular lens (IOL) insertion is usually not performed because calculation of the IOL power may not be exact and also to avoid any postoperative complications such as severe postoperative inflammation as is expected in such cases. Anterior capsule rim should be saved where possible, for future IOL implantation.
POSTERIOR INTRAOCULAR FOREIGN BODY –
External approach - Small magnetic IOFB in the region of the pars plana.
Accurate localization is necessary to mark the incision point. Preoperative Ultrasound biomicroscopy helps to localize the foreign body in the pars plana region. Careful conjunctival opening should be done, as the foreign body may be present just external to the eye in the sub-conjunctival space. If necessary the rectus muscles are isolated and tagged for better exposure. Either a partial-thickness scleral flap or a full-thickness sclerotomy is performed after localizing the IOFB precisely. Diathermy is applied to the choroid. A pre-placed mattress suture is placed. Anterior chamber paracentesis is performed to avoid any prolapse of intraocular contents. An external electromagnet is placed over the sclerotomy site and turned on. The choroid should tent indicating the magnetic IOFB is in this location. Occasionally, the IOFB will extrude through the choroid when the electromagnet is on; however, an incision in the choroid usually is necessary to allow for the IOFB to pass through the choroid. Diathermy at this point would be helpful to avoid any bleeding. If vitreous prolapses with the IOFB, sharp scissors are used to cut the vitreous. It is better to avoid cutting the prolapsed uveal tissue to avoid bleeding, prolapsed uveal tissue can be cauterized. When the IOFB is removed, the sclerotomy site is closed with the pre-placed mattress suture. Indirect ophthalmoscopy is performed to detect and treat any retinal tears that may be present. Major complications of the external approach are extrusion of intraocular contents with retinal incarceration and possible hemorrhage. Reducing the intraocular pressure with AC paracentesis and external pressure on the globe at the time of IOFB removal reduces this complication. Occasionally, the IOFB is difficult to remove with the external electromagnet because the magnetic strength is not sufficient to overcome the force holding the IOFB due to encapsulation. In such situations, an internal approach is recommended.
An internal approach is used in cases with opaque media and large, nonmagnetic, or subretinal IOFB that cannot be managed through an external approach.. A standard 3-port vitrectomy is performed. Sclerotomy incision should avoid the area of the entry wound to prevent further damage to intraocular tissues if any incarceration is suspected. The first goal of the vitrectomy is to remove any adhesions of the IOFB, to avoid any pull on the retina. Once the foreign body is free from all the adhesions, it can be removed with a forceps or a magnet. Before removing the foreign body, peripheral examination of the retina should be performed and removal of the peripheral vitreous is a must to avoid any traction while removing the foreign body through the sclerotomy. If the IOFB is larger than the sclerotomy site, enlargement of the sclerotomy in a circumferential direction may be necessary. A very large IOFB is best managed through a limbal incision after a lensectomy. A limbal or scleral tunnel is created, that should be large enough to accommodate the IOFB. The IOFB is grasped and brought into the AC through the pupil. The corneal endothelium should be protected. The infusion line is turned off to reduce the risk of iris prolapse. A second forceps is introduced through the limbal incision to grasp the IOFB and extract it out of the eye. The limbal incision is closed. If the IOFB is intraretinal or subretinal, the IOFB is grasped and removed through the retinal impact or entry site. Retinal blood vessels should be cauterized to avoid any pre-retinal or subretinal hemorrhage. If the foreign body is encapsulated, the capsule needs to be dissected with forceps or scissors. Once the foreign body is free from the capsule, it can be removed with a magnet or forceps through the sclerotomy. Care should be taken to avoid any injury to the peripheral retina while removing the IOFB through the sclerotomy. Retinal tears/retinal detachment can be caused by the foreign body or by manipulation during the procedure. Intravitreal antibiotics can be considered if infection is suspected.t
POST OPERATIVE CARE Routine postoperative care includes topical antibiotics, steroids, cycloplegics, and anti-glaucoma medications if required.
Corneal opacity Cataract Endophthalmitis Retinal tear/detachment/ Proliferative Vitreoretinopathy (PVR) Vitreous hemorrhage Optic neuropathy Siderosis Chalcosis Phthisis
Prognosis largely depends upon the location and size of the injury as well as the substance involved and the time of removal. Late presentation, vegetative matter and presence of an infection are poor prognostic factors.
References : (1) Albert & Jakobiec's Principles & Practice of Ophthalmology, 3rd Edition (2) The Retina - Stephen Ryan , 4th Edition (3) Current trends in the management of intraocular foreign bodies. Curr Opin Ophthalmol. 2008 May;19(3):225-33. (4) System of Ophthalmology - Duke-Elder