Ocular injury is an important cause of visual impairment. According to WHO estimates, eye trauma causes about 1.6 million cases of blindness and about 19 million cases of monocular blindness or reduced vision each year.
The estimated incidence of open-globe injury is 3.5 to 4.5 per 100,000 people, and rapid initial assessment is especially important among cases of post-traumatic visual impairment1).
During the acute trauma phase, swelling of the surrounding soft tissues, sedation, and impaired consciousness can make physical examination of the eye difficult. For this reason, imaging plays an important role in assessing the extent of injury.
The following main imaging techniques are used.
In the acute trauma phase, direct examination of the eye is often difficult because of swelling of the surrounding soft tissues, sedation, and impaired consciousness. Imaging can assess the extent of injury, the location of foreign bodies, and disruption of the ocular structures, providing essential information for deciding on treatment.
During the examination, the following findings are checked systematically.
In blast trauma (report from the Beirut port explosion), injury frequencies were ocular surface disease 54.2%, eyelid laceration 41.6%, orbital fracture 29.2%, hyphema 18.8%, and open-globe injury 20.8%2).
The types and frequencies of trauma are shown below.
The main indications and characteristics of each imaging modality are shown below.
| Modality | Main targets | Main features and benefits |
|---|---|---|
| Ultrasound | Vitreous, retina, choroid, IOFB | Noninvasive, low-cost, non-ionizing radiation |
| UBM | Deep anterior segment (iris, ciliary body) | High frequency, 5 mm penetration depth, contact method |
| Anterior segment OCT | Cornea, angle, ciliary body | Non-contact; also usable in penetrating trauma |
| Posterior segment OCT | Macula, retina, and choroid | Micrometer-level cross-sectional resolution |
| CT | Orbital fractures, foreign bodies, and globe rupture | Excellent for showing bone and metallic foreign bodies |
| MRI | Changes over time in soft tissue and hematoma | No ionizing radiation; contraindicated with magnetic materials |
Mundt and Hughes introduced A-mode in 1956, and Baum and Greenwood introduced B-mode in 1958. A 7.5–12 MHz probe is used; it is noninvasive, uses no ionizing radiation, is inexpensive, and is easy to perform.
Relative contraindication in open globe injury; primary closure is strongly recommended first. If it must be performed, sterilizing the probe is essential.
Findings for each structure are as follows.
Ultrasound is performed when hyphema is extensive and the fundus cannot be visualized. Good images cannot be obtained in eyes filled with silicone oil or gas.
Developed by Foster and Pavlin in the early 1990s. Using a high frequency of 30–60 MHz, it produces high-resolution tomographic images with a penetration depth of 4–5 mm and a resolution of 50 μm.
Even when corneal edema or opacity is present, it can visualize iridodialysis, angle recession, cyclodialysis, zonular rupture, scleral laceration, foreign bodies, and epithelial ingrowth. It is useful for detecting and localizing small, superficial nonmetallic foreign bodies that are often missed on CT or USG.
Assessing zonular deficiency before surgery for traumatic cataract makes it possible to plan ahead to prevent vitreous prolapse and lens drop.
After instilling topical oxybuprocaine anesthesia in the supine position, perform the exam using an eye cup or membrane method (UD-8060).
UBM
Penetration depth: 4–5 mm. The posterior surface of the iris and the ciliary body can be visualized.
Contact method: Contact is required during the examination. Use caution when performing it in penetrating injuries.
Corneal opacity: The anterior segment can be observed whether or not corneal opacity is present.
Anterior segment OCT
Noncontact: Uses 1310 nm long-wavelength light. Can also be performed in penetrating ocular trauma.
Resolution: High-resolution images of the corneal surface and the anterior chamber angle can be obtained.
Limitations: Cannot penetrate pigmented tissue, so structures deeper than the posterior pigment epithelium of the iris cannot be imaged.
This is a noncontact examination using 1310 nm long-wavelength light and can be performed even in penetrating eye trauma. It can show Descemet membrane detachment, angle closure, corneal stromal foreign bodies (up to 6 mm deep), ciliary body detachment clefts, corneal lacerations, and lens dislocation. It is an alternative when gonioscopy is difficult because of low intraocular pressure due to ciliary body detachment.
Uses 830 nm short-wavelength light. Useful for diagnosing and evaluating Berlin edema, traumatic macular hole, preretinal/submacular hemorrhage, retinal detachment, choroidal rupture and detachment, RPE tear, and traumatic retinoschisis.
False negatives and false positives are common, so its role is limited today. However, it is used as an aid for screening metallic foreign bodies. Waters view, orbital projection view, and the Comberg method are used to localize foreign bodies.
CT is a central test for evaluating orbital fractures, intraorbital foreign bodies, and globe rupture. Multiplanar assessment including coronal sections helps confirm the extent of fracture, the extraocular muscles, and the orbital contents.
The main indications and special notes for CT are as follows.
If a foreign body suspected to be metal (magnetic) remains on CT, MRI is contraindicated. Repeated imaging in young patients requires attention to radiation exposure. Iodinated contrast agents carry a risk of anaphylaxis and acute renal failure, and patients with eGFR < 45 mL/min/1.73m² need adequate preventive measures when undergoing contrast-enhanced CT.
It is better than CT for observing soft tissue and does not use ionizing radiation. It is excellent for detecting herniated fat in orbital floor fractures and showing soft tissue herniation and posterior extension. Absolutely contraindicated if a magnetic foreign body is suspected because of the risk of worsening from foreign body movement and heating. Plant foreign bodies may not be visible for a period if they contain little water. The imaging time is long, and claustrophobia and limited availability can be barriers.
The MRI signal characteristics of the eyeball are shown below.
| Site | T1 signal | T2 signal |
|---|---|---|
| Anterior chamber and vitreous | Low signal | High signal |
| Lens | Slightly high signal | Low signal |
| Retina and choroid | Slightly high signal | Low signal |
| Sclera | Low signal | Low signal |
In open-globe injury, ultrasound examination is a relative contraindication. Primary closure should be performed first, and this is strongly recommended. If it must be done, sterilizing the probe is essential, and care should be taken not to press the probe firmly. CT is also recommended as an alternative.
If a ferromagnetic foreign body is suspected, MRI is absolutely contraindicated. There is a risk of worsening due to movement of the foreign body and heating. First, evaluate the foreign body’s characteristics and location with CT, and consider MRI only after confirming that it is not ferromagnetic.
Because this condition is mainly about imaging diagnosis, describe how imaging contributes to deciding the treatment plan for each type of trauma.
Anterior segment injury occurs through a mechanism in which external force causes a sudden rise in intraocular pressure -> stretching of the corneoscleral limbus -> movement of aqueous humor posteriorly and toward the angle -> injury to the iris and ciliary body. In blunt globe rupture, increased intraocular pressure and shock waves create an indirect scleral wound parallel to the corneoscleral limbus, often posterior to the equator.
Because the choroid has poor distensibility, external pressure from a blow to the eye can cause circumferential tears in the posterior pole (especially around the optic disc). Traumatic optic neuropathy occurs when indirect force acts on the optic canal, causing vasogenic edema within the optic nerve tissue (a pathology similar to cerebral edema). It is not necessarily related to an optic canal fracture.
The MRI signal of a hematoma changes as follows.
| Stage | Time | T1 signal | T2 signal |
|---|---|---|---|
| Hyperacute phase | Up to 1 day (Oxy Hb) | Isointense to hypointense | Hyperintense |
| Acute phase | 1–3 days (Deoxy Hb) | Low signal | Low signal |
| Subacute phase | 3 days to 1 month (Met Hb) | High signal | High signal |
| Chronic phase | 1 month and later (Hemosiderin) | Low signal | Low signal |
Studies comparing early and delayed primary repair for open-globe injury have accumulated1). Imaging can help organize foreign bodies, globe configuration, and orbital fractures before surgery and assist in deciding the repair strategy.
Reports from the Beirut port explosion showed that explosive disasters can cause ocular surface injuries, eyelid lacerations, orbital fractures, hyphema, and open-globe injury at the same time2). Even in the acute phase, when life-saving care takes priority, a systematic ophthalmic assessment system is needed.
Sagittal MRI may provide helpful information for understanding the posterior extension of an orbital blowout fracture, but it is not the first-line choice in the acute phase because of scan-time and environmental limitations. The use of MRI without radiation exposure should be carefully considered after metallic foreign bodies have been ruled out.
