Recent Imaging Techniques in Ocular Trauma

Introduction

According to the World Health Organisation, eye injuries cause blindness in over 1.6 million individuals yearly, and unilateral blindness or reduced vision in approximately 19 million people. As many as 97 percent of trauma-related ocular injuries occur from blunt trauma, with the incidence of these injuries being between two and six percent overall.

Trauma-related face fractures increase the likelihood of concomitant eye injuries in patients, and facial fractures may account for up to ten percent of cases of vision loss and blindness. As many as 84 percent of individuals with head traumas may also experience ocular involvement.

Physical examination of the eye may be complex following acute trauma due to surrounding periorbital soft-tissue edema and other accompanying injuries, challenges with patient participation brought on by anesthesia, unresponsiveness, and changed state of mind. Imaging methods can determine the severity of injuries when these conditions are present.

What Are Recent Imaging Techniques in Ocular Trauma?

Following are some imaging methods utilized in ocular adnexal trauma:

1. USG (ultrasonography)

2. UBM (ultrasound-based microscopy)

3. OCT (optical coherence tomography)

4. FFA (fundus fluorescein angiography)

5. ICG (indocyanine green angiography)

6. Fundus Autofluorescence (FAF)

7. Plain x-ray

8. CT scan, or Computerized Tomography

9. MRI, or Magnetic Resonance Imaging

The diagnosis and follow-up of intraocular injuries may generally be assisted for orbit, optic nerve, and ocular adnexal injuries.

1. Ultrasonography

• A probe used in traditional ophthalmic ultrasonography (USG) oscillates between 7.5 and 12 Mega Hertz.

• Both the unidirectional amplitude modulated (A-scan), initially described in 1956 by Mundt and Hughes, and the two-directional cross-sectional brightness (B scan) scan, which Baum and Greenwood first used in diagnostic ocular ultrasonography in 1958, can be used.

• The A-scan and B-scan frequently work in tandem and complement one another. It is an affordable, simple, non-ionizing, and non-invasive imaging technology.

• In the presence of media opacity, it helps locate intraocular foreign bodies (IOFB) and highlights soft tissue abnormalities of the eye and orbit.

• It is often contraindicated to prevent further damage and wound infection when an open globe injury occurs.

• Therefore, it is strongly advised that primary closure be carried out before ultrasonography testing in case of a ruptured globe.

• Before primary closure, ultrasonography examinations should be cautiously conducted to reduce eye injuries. Sterility is imperative if the globe is open or a wound has recently been stitched up.

• The probes must be sterile. Otherwise, sterile rubber sleeves may be used to contain them.

2. UBM (Ultrasound-Based Microscopy)

• Alternative imaging modalities have become more popular due to conventional ultrasound B-Scan and high-resolution radiologic pictures' incapacity to see the anterior section.

• Foster and Pavlin created the first practical Ultrasound biomicroscopy (UBM) equipment in the early 1990s.

• UBM is an imaging method that creates high-resolution, cross-sectional pictures of the anterior segment to a depth of around 5 mm using high-frequency (35-50MHz) sound waves.

• In the case of a corneal disease like edema, keratoconus, or corneal scarring, UBM is also very valuable. Regardless of the opaque medium, it can show that intraocular structures have been disrupted, as in cases of iridodialysis, angle recession, cyclodialysis, zonular rupture, scleral laceration, foreign body, and epithelial ingrowth, and it can support the need for therapy.

• The real-time picture acquisition and in-situ visualization of the motion of diverse structures are additional benefits of UBM.

• In addition, high-frequency (50 MHZ) ultrasound is far more accurate than traditional low-frequency (10 MHZ) ultrasound for determining the precise location, size, and type of a foreign body.

3. FFA (Fundus Fluorescein Angiography)

• Depending on the underlying disease, angiographic results range from average to hypo to hypofluorescence.

• Fluorescein leakage, a sign of rupture of the RPE outer blood-retinal barrier, is seen in severe trauma situations.

• Mild injuries might only affect the outer segments of the photoreceptors without rupturing the blood-retinal wall. These may appear as window defects in late Retinal Pigment Epithelium (RPE) involvement with atrophic.

• Fluorescein angiography may reveal starry, pinpoint leakages in the sympathizing eye in situations of sympathetic ophthalmia.

• Following trauma, areas of retinal opacity with fluorescein leaking may take on the appearance of salt and pepper, correlating with a focused loss of retinal function that results in scotomas.

• To diagnose and predict the outcome of ocular damage involving the posterior portion of the eye, FFA is thus a beneficial tool.

4. OCT, or Optical Coherence Tomography

• Optical coherence tomography (OCT), a non-contact, high-resolution, cross-sectional imaging technique, uses the low coherence interferometry concept.

• It is capable of axial resolutions between 3 and 20 m. Compared to anterior segment OCT (ASOCT), posterior segment OCT (PSOCT) employs light with a lower wavelength of 830 nm.

• ASOCT supports the identification of intraocular diseases and ocular surface damage in cases of ocular trauma.

• Since it is a non-contact imaging approach, it offers the advantages of precision, reproducibility, and suitability for penetrating ocular lesions.

• It is possible to monitor and diagnose macular and chorioretinal disease with great accuracy and precision using posterior segment OCT, which is simple, rapid, and trustworthy.

5. ICG (Indocyanine Green Angiography)

• Indocyanine Green Angiography (ICG) is a superb diagnostic technique to assess choroidal diseases.

• The typical symptoms of choroidal injury include characteristics like localized delayed filling along the choroidal arteries and delayed filling of choroidal veins.

• Additionally, intrachoroidal ICG may leak surrounding arteries, especially vortex veins, which denotes choroid-draining vein injury.

• The indocyanine green leakage location, which frequently corresponds with the fluorescein leakage, is where it is most common to see dilatation of tiny choroidal arteries, constriction, and uneven choriocapillaris diameters.

• The outer blood-retinal barrier may have broken down in the presence of such ICG results, although it has also been suggested that trauma may have enhanced the choriocapillaris' permeability.

6. Fundus Autofluorescence (FAF)

• A non-invasive technique for evaluating alterations in the posterior portion of the eye brought on by traumatic ocular trauma is fundus autofluorescence (FAF) imaging.

• It is a beneficial in-vivo mapping of fluorophores in the ocular fundus, naturally or abnormally.

7. Plain X-ray

• Modern times limit the use of plain X-rays in ocular trauma. It was formerly the go-to imaging technique for diagnosing orbital and orbitofacial fractures.

8. CT scan or Computerized Tomography

• It is used for diagnosing possible orbital and orofacial fractures, intraorbital and intraocular foreign bodies, and traumatic optic neuropathies.

9. MRI, or Magnetic Resonance Imaging

• Because of its limited use in ocular and adnexal trauma, magnetic resonance imaging is seldom recommended in acute posttraumatic situations.

• Additionally, it is advised once metallic magnetizable, foreign bodies of the face, orbits, and other body parts have been categorically ruled out using a CT scan, X-ray, or ultrasound.

Conclusion

In conclusion, a thorough understanding of the numerous imaging methods for the eyes and ocular adnexa, with cautious and appropriate use of investigative techniques, relative and absolute contraindications, and interpretation, facilitates the development of a comprehensive diagnosis of structural abnormalities. This helps the doctor provide the patient with the most suitable treatment by assisting in establishing a more thorough diagnosis as well as patient counseling, followed by the proper investigation and management. In addition to comprehensive, painless, and non-traumatic ocular and orofacial examinations, the adequate use of imaging aids in formulating a complete diagnosis, enabling patient counseling, treatment planning, and postoperative patient monitoring.