Computerized axial tomography in the detection of intraocular foreign bodies

Computed Tomography Diagnostic Abilities for Open-Globe Injuries in Pediatric Versus Adult Patients

OBJECTIVES

The aim of this study was to compare the role of computed tomography (CT) in the diagnosis of open-globe trauma and intraocular foreign body (IOFB) in pediatric and adult age groups.

METHODS

Medical records of cases with open-globe trauma at Inonu University Hospital's Ophthalmology Emergency Service were retrospectively evaluated. Preoperative orbital CT images of the cases obtained at emergency services and their clinical and/or surgical findings were compared in pediatric and adult groups.

RESULTS

We included 47 eyes of 47 cases aged 18 years and below (pediatric group) and 85 eyes of 82 cases over 18 years (adult group). The mean ± SD age was 10.80 ± 5.11 years (range, 2-18 years) in the pediatric group and 46.34 ± 19.01 years (range, 19-82 years) in the adult group. Computed tomography images revealed 21.7% of the cases with corneal lacerations, 55.5% with scleral lacerations, and 91.6% with corneoscleral lacerations in the pediatric group, whereas the respective numbers were 48.4%, 66.6%, and 61.9% in the adult group. The detection rates of corneal penetrations and vitreous hemorrhage with CT were significantly lower in the pediatric group than in the adult group (P < 0.05). The CT scans diagnosed 66.6% of the pediatric cases and 90% of the adult cases with an IOFB.

CONCLUSIONS

Corneal lacerations and IOFBs can be missed, especially in the pediatric group, because the eye is smaller in adults. Pediatric patients with a history of ocular trauma should undergo an examination under general anesthesia followed by surgical exploration if necessary.

Computed tomography in the diagnosis and prognosis of open-globe injuries

OBJECTIVE

Determine sensitivity, specificity, and prognostic signs of orbital and ocular computed tomography (CT) in diagnosing patients with open globe injury.

DESIGN

Randomized masked review of computed tomograms and retrospective clinical correlation of patients with ocular trauma.

PARTICIPANTS

Two hundred patients who underwent CT evaluation for ocular trauma between 1989 and 1993.

METHODS

CTs were read by three masked observers; findings were tabulated and compared for variability among observers; sensitivity and specificity were calculated and CT findings were grouped according to visual outcome retrieved from record review.

RESULTS

In the absence of clinical information, sensitivity and specificity were 75% and 93%, respectively. The positive predictive value ranged from 88% to 97%, with a calculated overall positive predictive value of 95%. Patients who had a poor visual outcome (visual acuity <2/200) or who underwent enucleation had significantly more CT findings than patients with a good visual outcome. Vitreous hemorrhage, absence of lens, and severe distortion of vitreous space are among the most common CT findings associated with poor visual outcome.

CONCLUSIONS

CT is not sensitive enough to be solely relied upon for diagnosis of all open globe injuries. CT findings only complement clinical findings, increasing the clinician's overall ability to make an accurate diagnosis of open globe injury, and may provide useful prognostic information regarding visual outcome.

Orbital helical computed tomography in the diagnosis and management of eye trauma

OBJECTIVE

To prospectively determine the accuracy of helical computed tomography (CT) and multiplanar reconstruction and its value in surgical planning for the management of ocular trauma with suspected intraocular and orbital foreign bodies using surgical and clinical follow-up findings as the gold standard.

DESIGN

Prospective, observational case series.

PARTICIPANTS

Thirty-six patients with ocular trauma and suspected foreign bodies were studied.

INTERVENTION

All patients were examined using a standardized scanning protocol with helical CT direct scanning in the axial plane and multiplanar reconstruction of coronal and sagittal planes.

MAIN OUTCOME MEASURES

The images were analyzed for the presence and number of intraocular and orbital foreign bodies, anatomic location, and foreign body size. The surgical and clinical follow-up findings (contact lens examination, gonioscopy, indirect ophthalmoscopy and scleral depression, perimetry, color testing, measurement of size) were used as the gold standard to which the image results were compared.

RESULTS

Helical CT showed a single intraocular foreign body in 14 patients, a single orbital foreign body in 9 patients, and multiple orbital foreign bodies in 2 patients. Intraocular or orbital foreign bodies were excluded in 11 patients. Twenty foreign bodies were correlated with surgical results. Surgical and clinical follow-up findings were in agreement with helical CT results regarding the detection and determination of the number of presumed foreign bodies. Localization to intraocular versus orbital compartment and proximity to the optic nerve was accurate in all patients. Determination of size of the foreign bodies on the helical CT images was reliable and repeatable.

CONCLUSIONS

Helical CT axial scanning with multiplanar reconstruction is accurate at detecting and localizing intraocular and orbital metallic, glass, and stone foreign bodies. This imaging method aids the surgeon in choosing the surgical approach to retained intraocular and orbital foreign bodies.

Controversies in the management of open-globe injuries involving the posterior segment

There are numerous unresolved issues and controversies regarding the management of open-globe injuries involving the posterior segment. These areas include, but are not limited to, the following issues. Although vitrectomy has been shown to improve visual outcomes and allow retention of the eye in many cases, the extent of visual improvement is often limited because of the nature of the injury. Timing of vitrectomy surgery has been and will continue to be debated by proponents of early versus delayed intervention. The multiple features of acute ocular injury make it very difficult to interpret retrospective data regarding the most appropriate timing for surgical intervention. The use of prophylactic cryotherapy, in the setting of a scleral laceration with possible retinal damage, is not as controversial at present, as there is now sufficient data indicating that cryotherapy may actually exacerbate intraocular proliferation and worsen the situation. The role and benefit of a prophylactic scleral buckle is very widely contested, and it is not known if it truly decreases the risk of subsequent retinal detachment. Another area of debate centers on the use of antibiotics. When there is a known clinical infection, intravitreal antibiotics are the mainstays of therapy. However, in the absence of clinical infection, the use of prophylactic antibiotics and their routes of administration are quite controversial. Although there are significant data regarding the use of antibiotics in the postoperative setting, this information cannot be extrapolated into the setting of open-globe injuries, as organisms and virulence factors differ. Similarly, the use of vitrectomy versus vitreous tap in the setting of traumatic endophthalmitis is not fully resolved, although vitrectomy is used in most cases to repair concurrent damage from the injury itself. Finally, the placement of intraocular lenses in the acute trauma setting is controversial, as the risk of complications is quite high. Prospective, controlled clinical studies have not been done. This article reviews pertinent data regarding these management issues and controversies, and provides recommendations for treatment based on the available published data and the authors' personal experience.

Evaluation of intraocular foreign bodies by spiral computed tomography and multiplanar reconstruction

OBJECTIVE

This study aimed to evaluate the ability of spiral computed tomography (CT) and multiplanar reconstruction in the assessment of intraocular foreign bodies.

DESIGN

The study design was experimental.

MATERIAL

Three foreign bodies (metal, glass, and plastic) implanted into the globe of a cadaveric head were studied.

INTERVENTION

Spiral CT in the axial plane was used. Beam collimation and table increment were both 3 mm, whereby overlapping axial slices were reconstructed at 1-mm intervals. The data were transferred to a workstation, and reconstructions in the coronal and sagittal plane were performed.

MAIN OUTCOME MEASURES

The ability to detect and evaluate localization, shape, and size of the foreign bodies in all three imaging planes was assessed.

RESULTS

All foreign bodies were detected in the axial and in both reconstructed planes. The metal foreign body caused imaging artifacts in the axial plane. In the reconstructed planes. imaging artifacts were less severe, and evaluation of localization and shape was improved. Glass and plastic foreign bodies were well seen in all planes, and shape and localization were well demonstrated. Appropriate window settings improved determination of size of the different foreign bodies.

CONCLUSIONS

Spiral CT of the orbit and multiplanar reconstruction offers a promising tool for evaluation of intraocular foreign bodies. Advantages of spiral CT compared to conventional CT are data acquisition in only one axial plane; shortened examination time; reduced radiation exposure; reduced imaging artifacts from metallic foreign bodies in the reconstructed planes; and demonstration of localization, shape, and size of the foreign body in three imaging planes.

Ocular siderosis

The authors report their experience in the management of 8 patients with ocular siderosis due to a retained intraocular foreign body (IOFB). All patients were male, aged between 19 and 39 years. Seven had a definite history of trauma; 3 had presented at the time of injury to a casualty department, and the diagnosis had been missed. The interval between injury and diagnosis ranged from 2 to 24 months. IOFB removal was performed in 7 patients: through a sclerotomy and magnet or foreign body forceps in 4 eyes and via a pars plana vitrectomy and intraocular foreign body forceps in 3 eyes. Cataract extraction was performed in 4 patients. Histological examination of specimens removed at the time of surgery showed iron deposition in the conjunctiva, anterior lens capsule and pars plana. Transmission electron microscope X-ray microanalysis showed that iron was contained in siderosomes, intracytoplasmic membrane-bound dense bodies. Final visual acuity was 6/12 or better in 6 patients and reduced to light perception in the remaining 2 due to proliferative vitreoretinopathy.

Ultrastructural studies of cornea, iris and lens in a case of siderosis bulbi

Transmission electron microscopy studies of cornea, iris and lens from a case of ocular siderosis due to a retained intraocular foreign body (IOFB) and vitreous hemorrhage are presented. We observed widespread degeneration of lens epithelium, iris stromal cells and iris pigment epithelium associated with intra- and extracellular siderosomes. A direct relationship was found between the degree of cell degeneration and the number of intracellular siderosomes in lens epithelium. This is contrary to findings in other siderotic tissues which show intracellular iron deposition to be associated with increased ability to detoxify iron. The cornea showed siderosomes only within keratocytes, and there was no evidence of a relationship between siderosome accumulation and cell degeneration. The literature on ultrastructural studies of ocular siderosis is reviewed and the current theory of the mechanism of chronic iron toxicity is discussed.

Limitations of computerized tomography in the localization of intraocular foreign bodies

Computerized tomography (CT) scanning was used to evaluate nine patients with intraocular foreign bodies. We found that significant limitations of this method still exist, even with high resolution scanners, in the localization of extremely small, multiple or relatively radiolucent foreign bodies and those located near the ocular wall.

Computed tomography in penetrating injury to the eye

We used computed tomography to detect and localize foreign bodies in two unusual cases of penetrating injury to the eyes. In one case, a large broken twig appeared to have penetrated the globe and the inferior rectus muscle; in the other, the globe was ruptured by many glass shards . In the first case surgery showed the computed tomographic impression to be incorrect. The globe and the inferior rectus muscle were intact and vision and motility were normal postoperatively. In the second case, swelling made direct visualization impossible, and computed tomography was used to locate the foreign bodies.

Unexplained heterochromia. Intraocular foreign body demonstrated by computed tomography

Standard radiographic techniques are often inadequate in demonstrating the presence and location of intraocular foreign bodies. Computerized axial tomography was used to confirm the presence of a metallic foreign body in a patient with heterochromia iridis and suspected ocular siderosis in whom no foreign material was found by conventional examination methods.

Computed tomography in choroidal detachment

Computed tomography proved valuable in localizing and differentiating serous or hemorrhagic choroidal detachment and scleral infolding. The mean attenuation values (CT numbers) in the region of fresh hemorrhagic choroidal detachment were 74 Hounsfield units (HU). The 90% confirmation limit of the mean was 55 to 84 HU. For serosanguineous choroidal detachment, the mean was 50 HU, with a 90% confirmation limit of 46 to 54 HU. For serous choroidal detachment the mean was 46 HU, with a 90% confirmation limit of 39 to 53 HU. Inflammatory choroidal detachment showed uveoscleral enhancement, which in cross section appeared as a ring (ring sign), and subchoroidal or intrauveal accumulation of fluid. Ocular hypotony produced the characteristic CT "umbrella sign."