Case Report: Ophthalmia Nodosa Caused by Caterpillar Setae

ABSTRACT.

Caterpillars can damage human health, including visual acuity, as a result of penetration of the setae into the eye or their layout on the eye tissue. However, the path of setae movement in the eye remains unclear. In this study, a 43-year-old woman was injured in the left eye by a caterpillar. Other than rubbing her eye, the patient did not attempt any type of treatment, and she visited our outpatient clinic 5 days after the accident. The patient’s left eyelid was markedly swollen, with a visual acuity of 1.0 in the right eye and only 0.04 in the left eye. Images of the setae in the eye were taken using an oil lens microscope, which showed clearly their detailed characteristics. The setae were removed from the eye as much as possible. Topical eyedrops and oral steroids were used to reduce the inflammation. Vitritis and retinitis occurred at the 6-month follow-up and was classified as ophthalmia nodosa by the ophthalmologist. Before we did our study, some ophthalmologists believed that setae moved forward; however, we found that setae in the eye moved in a disorderly fashion. We also note that all setae should be removed. This case demonstrates that caterpillar setae in the eye move in a disorderly fashion and eventually caused ophthalmia nodosa.

INTRODUCTION

This report describes the consequences after the penetration of caterpillar setae into the eyeball of a patient that caused ophthalmia nodosa and consequent severe visual acuity loss after 5 months. The aim of this report is to call attention to the possibility of caterpillar setae penetration in the eye. It remains controversial, as a result of inadvertent iatrogenic injury, whether all setae should be removed in such situations. Experience and lessons learned from this case tell us that complete removal of all setae is required at the very first debridement.

CASE REPORT

A 43-year-old woman from a rural area wiped the sweat from her left eye with her arm while working in the field, which resulted in pain, tears, and redness occurring immediately in that eye. The patient discovered that a caterpillar had been on her arm when she wiped her eye. She did not seek therapeutic measures, but continued to rub her eye.

The patient visited our outpatient clinic 5 days after the accident. The visual acuity of the right eye and the left eye was 1.0 and 0.04, respectively. The left eyelid was clearly swollen, and it was difficult to open this eye. The conjunctiva of the left eye was congested, and 60 caterpillar setae were eventually found in the eyelid conjunctiva, bulbar conjunctiva, and cornea. The epithelial tissue of the cornea was severely scraped (Figure 1). Topical anesthesia with proparacaine was administered as eye drops and the setae were removed using a slit lamp. Twenty setae were removed from the palpebrae, 26 setae were removed from the cornea and conjunctiva, six setae were removed from the anterior chamber and iris, two setae penetrated the cornea (Figure 2), and two setae were located on the root of the iris. These latter two setae were wrapped in fibrin, and bleeding occurred when we tried to force them out (Figure 3). A viscoelastic agent was injected into the anterior chamber of the eye to stop the bleeding, but debridement was abandoned because of the occurrence of this problem.

Figure 1.

Setae in the cornea (white arrows). The epithelium of the cornea was severely scraped (black arrow).

Figure 2.

(Left) Optical coherence tomography (OTC) of the cornea. The green arrow is the direction of the OCT scan. (Right) Setae in the anterior chamber visualized by OTC (white arrow).

Figure 3.

Setae in the iris (white arrows). Bleeding occurred in the anterior chamber when we pulled out the setae buried in the iris (green arrow).

Some setae remained in the fornix conjunctiva and subconjunctival bulbar conjunctiva after debridement. They were not removed because they were completely buried and the conjunctiva was seriously damaged. Levofloxacin eye drops and fluorometholone eye drops were administered four times a day, locally, after surgery. Visual acuity in the left eye increased to 0.4 after 6 days. Monitoring of the eye during the subsequent three visits revealed that the setae moved every 3 days. Some setae located in the conjunctiva moved to a superficial position, which allowed us to remove them using a slit lamp. One seta on the root of the iris disappeared, and one seta appeared in the front vitreous cavity (Figure 4). One seta moved from the nasal iris to the lower edge of the pupil, and three setae migrated from the subconjunctiva to the superficial layer of the conjunctiva after 10 days. All these setae were removed using a slit lamp.

Figure 4.

Seta in the vitreous body (white arrow).

The setae with its tip in the anterior chamber moved to the iris surface after 1 month, and the deep stromal foreign body moved to the corneal epithelium and was removed using a slit lamp. We asked the patient to return for evaluation every 3 days, but she did not comply.

Five months after the injury, the visual acuity of the affected eye decreased for the first time, from 0.4 to 0.2. Conjunctival congestion of the left eye was observed, and floating cells were visible in the anterior chamber. Vitreous floaters were present in the anterior chamber, and posterior synechiae were noted. Thus, the posterior section of the eye could not be seen (Figure 5). Edema was seen in the fovea when optical coherence tomography was used to scan the cornea (Figure 6). The patient was treated with fluorometholone eye drops once per hour, atropine eye gel three times per day, and oral prednisone tablets 40 mg once per day in the morning. The patient did not return for subsequent examination, so it is unknown whether she adhered to her medication treatments as prescribed.

Figure 5.

Posterior synechia.

Figure 6.

Edema in the fovea. (Left) Indicates the direction of the retina OCT scan. (Right) Indicates the edema of the fovea by the OCT scan.

DISCUSSION

Caterpillars belong to the order Lepidoptera, the second largest order of insects in the phylum Arthropoda. This order comprises approximately 160,000 species organized in 43 superfamilies, with 133 families distributed worldwide. The most frequent clinical manifestation caused by caterpillar poisoning is the development of contact dermatitis, which is characterized by extensive local inflammation with swelling, redness, and itching at the site of poisoning.¹ Caterpillar poisoning represents an emerging public health issue of international concern.² The symptoms in the eye are the same, and there are several clinical case reports of caterpillar poisoning in the eye.^3,4

Caterpillar setae affect the eye, causing redness and itching, along with pain and tears. Sridhar and Ramakrishnan⁵ reported that ophthalmologists should examine carefully the presence of setae in the superior and inferior tarsal conjunctiva in patients with unilateral redness.

Caterpillar setae in our patient were indeed found on the conjunctival surface of the upper eyelid after turning back the upper eyelid. Although one report⁶ suggested that all setae should be removed, unexpected difficulties arose in attempts to do this for our patient. Setae were first removed using a slit lamp microscope, which facilitated the detection of foreign bodies. After the removal of more than 20 root setae using the slit lamp, it became more difficult to continue the surgery because the surgeon had to keep both hands up during the surgery. Therefore, the patient was taken to the operating room. During the operation, we realized that the setae of this caterpillar were extremely brittle and would break when grabbed with forceps. Some foreign bodies were buried completely in the corneal stroma. The superficial foreign bodies were removed by cutting the surface with a scalpel and picking them out with forceps. However, the deep corneal setae were not removed to avoid further iatrogenic corneal damage.

The patient was instructed to visit the hospital every 3 days during the postoperative follow-up period because the remaining setae were displaced significantly after 3–5 days. The setae did not move from their own base toward the tip, as was expected. Indeed, the movement of the setae was irregular in terms of trajectory. This situation might be related to an inflammatory reaction at the base of the setae, the movement of the eyeball, or even a rejection reaction. Unfortunately, follow-up visits became less frequent after the first three visits as a result of patient noncompliance, even though we told her no payment was needed for subsequent visits.

Although the patient was not treated with oral glucocorticoids, the first vision loss occurred after 5 months. In addition to evident inflammation of the iris, the lens appeared cloudy, the vitreous was inflamed, and edema was present in the macular area of the retina. Our speculation was that these changes were caused by movement of the setae and gradual release of venom from them. Observations made using an oil lens microscope revealed the setae were hollow from the tip to the base (Figure 7), and this region contained the venom that caused allergic and toxic reactions.

Figure 7.

Setae under the oil lens of an Olympus microscope (CKX31/41, Olympus Corporation, Japan) at ×60 magnification.

The patient’s symptoms would have become more severe if the setae had penetrated throughout the eye. The entire spectrum of clinical findings was first described as “caterpillar-hair ophthalmia” by Pagenstecher in 1883, and later by Saemisch as “ophthalmia nodosa.”⁷ The spectrum of ocular pathologies caused by caterpillar setae was classified into five types by Cadera et al.⁸ The most severe type is vitreoretinal involvement (early or late). The setae enter the vitreous cavity through the anterior chamber, iris, and lens or by transscleral migration, causing vitritis, cystoid macular edema, or endophthalmitis. Our patient developed vitritis and retinitis at 6 months of follow-up, which the ophthalmologist classified as ophthalmia nodosa.

During the last visit, we were unable to persuade the patient to undergo a vitrectomy to remove the setae in the vitreous and save visual acuity of the left eye. We regret the outcome. It is likely that the patient would not have lost her sight if we had removed all the setae, although the risk of iatrogenic damage resulting from surgery was considered. The setae in the eye move in a disorderly fashion, eventually leading to ophthalmia nodosa.