Anterior segment optical coherence tomography-assisted surgical planning of an organic intralamellar corneal foreign body removal: a case report

Ocular injury is the most common reason for emergency interventions in ophthalmology departments worldwide, and the second most common cause of visual loss [1, 2]. Corneal foreign bodies have been reported to be the second most common type of ocular injury [3]. Some materials, such as sand and glass, are well tolerated in the cornea without provoking a reaction. In such cases, an inert foreign body does not necessarily have to be removed but requires close monitoring. However, if an inert corneal foreign body is in the visual axis and/or reduces visual acuity, it has to be removed promptly [4]. Other materials, including metal and organic substances such as vegetables or wood, are poorly tolerated by the cornea and cause localized edema, inflammatory reaction, opacification, vascularization, and stromal necrosis [5].

Anterior segment optical coherence tomography (AS-OCT) is a noncontact, noninvasive imaging method that provides high-resolution, real-time, in situ visualization of tissue microstructure [6, 7]. It is a valuable tool for early diagnosis and for monitoring the progress of treatment in cases of ocular trauma [8] and causes minimal discomfort to trauma patients [9].

We report of the diagnosis, management, and follow-up of a patient with a reed foreign body in the cornea.

A 37-year-old male patient presented with a corneal foreign body in his right eye at the emergency eye unit of the Department of Ophthalmology of Semmelweis University. The incident occurred after he stumbled and fell onto a reed during a hike and the reed stabbed his right eye. Visual acuity at presentation was 20/25 Snellen with pinhole correction on the right eye, and 20/20 without correction on the unaffected left eye. Slit-lamp biomicroscopy of the right eye revealed a reed foreign body in the cornea, with an entry wound in the pupillary area nasally from the optical center. At the entry wound, less than 1 mm of the foreign body stood out. The other end of the foreign body was at the limbus at 3 o’clock. No flare or cells were detected in the anterior chamber. Both pupils were round, regular, and equally reactive to light. The lens was clear. Slit-lamp findings on the left eye and fundoscopy of both eyes were unremarkable. AS-OCT was performed using the Heidelberg-Spectralis (Heidelberg Engineering GmbH, Heidelberg, Germany) spectral-domain OCT device, using the Anterior Segment Module. The examination showed the foreign body 192–299 µm deep from the corneal epithelium in the stroma, with 53–80 µm of thickness (Fig. 1). The corneal endothelium was intact. Observation of the anterior chamber angle showed no abnormalities. It was necessary to remove the foreign body due to both its organic nature and the location.

Using the AS-OCT scans, we devised two plans for the removal of the foreign body: First, we planned to pull the foreign body from either end leaving the overlaying anterior stroma and epithelium intact. Second, in case the first attempt failed, we planned a direct incision over the foreign body and a removal through that surgical opening as an alternative strategy. On the OCT scans it could be seen that approximately the posterior third of the corneal stroma was intact, allowing for a direct incision without the risk of perforation into the anterior chamber.

During the operation, the attempt to pull out the foreign body from either end failed as the ends of the reed broke off due to its natural structure. The foreign body was eventually removed according to the OCT-assisted alternative plan via an incision made with a LaserEdge 2.85-mm Clear Corneal Knife (Bausch & Lomb Inc. Rochester, NY, USA) above and along the middle axis of the entire foreign body. Through this surgical wound, the foreign body was easily removed using a surgical forceps. The wound was then thoroughly washed with povidone-iodine. As the wound edges were surgically made and were aligning nicely, we decided not to apply sutures on the wound. At the end of the operation a therapeutic soft contact lens was placed on the eye surface (Supplementary Video 1).

Postoperative treatment consisted of 5 mg/mL topical levofloxacin five times a day and 10 mg/mL cyclopentolate drops twice daily.

A yellowish discharge appeared in the right eye 2 days after surgery. A sample was taken from the conjunctiva and the cornea for microbiological culture, which was negative for both bacteria and fungi. Therapy was not changed. After a few days, the inflammation gradually decreased, the wound healed nicely with a surrounding edema at the wound edges, and a superficial scar tissue in a narrow band around the wound started to form (Fig. 2). At this point, best corrected visual acuity with −0.75 D cylindrical correction at an axis of 180 degrees was 20/20. The patient was followed up postoperatively for about 2 years; he had no complaints and retained 20/20 visual acuity with minimal remaining astigmatism.

Ocular injury with a corneal foreign body is a common ophthalmic emergency. In most cases, slit-lamp examination is sufficient for the diagnosis and the removal of the corneal foreign body, but in rare cases other investigations are required such as AS-OCT or ultrasound biomicroscopy (UBM) [9, 10].

The AS-OCT examination may reveal unexpected lesions that are invisible or difficult to recognize with a routine slit-lamp examination [6]. Although high-frequency UBM could have revealed such clinical information, it should be emphasized that UBM can only be performed in cases of a sealed perforated cornea, scleral laceration, or partial-thickness laceration because of the pressure induced by the water bath and the risk of contamination [10].

An AS-OCT examination is useful in the planning of surgery of intra-corneal foreign bodies and in the follow-up [11]. It facilitates quantitative assessment of the remaining corneal width and allows one to assess the risk of impending perforation [9]. In our case, AS-OCT was extremely useful. The preoperative AS-OCT confirmed that the foreign body did not perforate the cornea completely, which was not seen clearly with slit-lamp biomicroscopy. We could determine the exact location, size, and depth of the corneal foreign body, assess the surrounding ocular structure, and plan the optimal surgical approach and determine the need for sutures. With the detailed information provided by AS-OCT, we were able to avoid open globe surgery.

The challenges and limitations of using AS-OCT in planning intra-corneal foreign body removal lie in the device’s ability to accurately identify the size, position, and penetration depth of the foreign body. Foreign bodies of various compositions may have different optical penetration properties and OCT characteristics and they may produce different imaging artifacts, as described by Armarnik et al. [12] Pencil graphite, metals, and wood demonstrate a hyper-reflective anterior border, but imaging of the posterior border could be challenging due to a shadowing effect. Wood usually appears as a hyper-reflective mass with various degree of penetrability depending on the concentration of the material. Pencil graphite and metals may produce a mirroring effect, making it difficult to assess the depth of penetration. Transparent materials (such as glass or plastic) usually demonstrate hyper-reflective sharp borders when surrounded by air or fluid, but when they are embedded purely in the corneal stroma, imaging might prove challenging. In certain cases when the composition of the foreign body is not known, these OCT characteristics might help distinguish them and assist in the decision-making regarding the need for or the urgency of the removal [12].

In certain cases of corneal lesions, anterior segment (AS) optical coherence tomography (OCT) might be essential in planning the surgery. In the present case, based on the information we obtained from the OCT scans, the corneal foreign body was removed via an external route without the need for sutures, providing the optimal outcome with no significant unwanted refractive changes.