Ophthalmia nodosa is a disease in which setae (hairs) from animals or plants penetrate ocular tissues and cause granulomatous inflammation. The term “nodosa” is Latin for “nodular,” referring to the granulomatous nodules that form around the setae.
The most common cause is caterpillar setae. The pine processionary caterpillar and tussock moth larvae are well-known causative organisms. Additionally, tarantula urticating hairs and plant spines (e.g., cactus) can also be causes.
Based on the depth of ocular penetration and clinical presentation, it is classified into five types (Type I to V). This classification is directly linked to treatment decisions and is therefore clinically very important1).
| Type | Lesion site | Clinical features |
|---|---|---|
| I | Conjunctiva (acute) | Acute conjunctivitis |
| II | Conjunctiva (chronic) | Chronic granulomatous conjunctivitis |
| III | Cornea | Corneal hairs and infiltration |
| IV | Anterior chamber and iris | Iritis and hairs in the anterior chamber |
| V | Vitreous body / Retina | Vitreitis / Retinal complications |
Cases have been reported worldwide, showing seasonality consistent with the habitat of caterpillars. Onset is concentrated in the spring to summer caterpillar activity period. In Nepal, seasonal hyperacute panuveitis (SHAPU) occurs epidemically due to moth setae 1).
Setae can be dispersed by wind, so they can reach the eyes even without direct contact with a caterpillar. The setae of the pine processionary caterpillar are fine and lightweight, and cases of airborne exposure are known. Wearing protective glasses is recommended in environments where caterpillars are present.
The severity of symptoms varies depending on the disease type.
Anterior Segment Findings
Conjunctival injection and papillary reaction: Main findings in the acute phase (Type I).
Conjunctival granuloma: Chronic granuloma around the hair. Characteristic of Type II.
Corneal hairs: Directly observable with a slit lamp. Found in the corneal epithelium to stroma.
Corneal infiltration and neovascularization: Appear in prolonged cases.
Posterior Segment Findings
Anterior chamber inflammation and iris nodules: Findings when hairs reach the anterior chamber (Type IV).
Vitreous opacities: Early finding of Type V. Indicates migration of hairs into the vitreous.
Vitreous hemorrhage and tractional retinal detachment: Most severe Type V complications5).
Tamilarsan et al. (2022) reported 4 cases (males aged 18–24) of corneal hair insertion due to insect collision while riding a motorcycle. All cases showed Type III–IV findings, and visual acuity ranged from 6/6 to 6/602).
Zou et al. (2025) reported a severe case in a 12-year-old boy caused by hairs from a tussock moth cocoon. He developed vitreous hemorrhage and tractional retinal detachment 13 months after injury, the most severe Type V case5).
The most effective method is to ride with the visor of a full-face helmet closed. Wearing goggles or protective glasses is also recommended. Insect activity is particularly high in the evening and at night, so caution is needed2).
Confirming a history of exposure to caterpillars or insects is most important. Inquire about occupation, outdoor activities, season, and the presence of pets (tarantulas). In children, the exposure history is often unclear4).
The gold standard for diagnosis is direct observation of the hair under a slit-lamp microscope. Multimodal imaging is useful for evaluating deep hairs 1).
| Examination | Target of Evaluation | Features |
|---|---|---|
| Slit-lamp microscope | Conjunctiva, cornea, anterior chamber | Direct observation of hairs |
| Anterior segment optical coherence tomography (AS-OCT) | Intracorneal hairs | Useful for depth assessment 1) |
| Ultrasound biomicroscopy (UBM) | Hairs in anterior chamber and iris | Detection of deep foreign bodies |
Ashkenazy et al. (2022) performed multimodal imaging combining AS-OCT, B-scan, FA, fundus autofluorescence, and SD-OCT in a Type V case caused by caterpillar setae, demonstrating that the localization of setae and the extent of intraocular inflammation can be assessed noninvasively 1).
Treatment is determined based on the Cadera classification.
Conservative Treatment
Type I (acute conjunctivitis): Removal of setae by irrigation. Combined with topical steroid and antibiotic eye drops.
Type II (chronic granuloma): Removal of setae within the granuloma using forceps. Anti-inflammatory treatment with topical steroids.
Type III (corneal setae): Superficial setae are removed with forceps. Deep setae are observed, and steroid eye drops are used when inflammation occurs 2).
Invasive Treatment
Type IV (anterior chamber setae): Removal of setae by anterior chamber wash 4). Combined with mydriatic and steroid eye drops.
Type V (vitreous/retina): Vitrectomy (PPV) + intraocular foreign body removal. Endolaser or gas tamponade is added as needed 5).
Levy et al. (2023) reported a 15-year-old girl whose cornea and conjunctiva were penetrated by setae from a white-marked tussock caterpillar. Setae removal and bandage contact lens placement were performed in the operating room, and she healed within 2 weeks 3).
Al Somali et al. (2021) reported a case of a 2-year-old girl with caterpillar setae found in the conjunctiva, cornea, and anterior chamber. Anterior chamber irrigation was performed under general anesthesia, but recurrence occurred 4 months later requiring reoperation. This was the first reported case in the Middle East 4).
Due to their barbed structure, setae are not naturally expelled from the body. They tend to migrate deeper into the eye due to body temperature and contraction of surrounding tissues. Even setae on the conjunctival surface may progress into the cornea or anterior chamber over time.
Recurrence can occur if tiny setae remain or if setae migrate deeper. In the report by Al Somali et al., recurrence occurred 4 months after initial anterior chamber irrigation, requiring reoperation 4). Regular follow-up is important.
Caterpillar setae are tiny structures about 100–200 μm in length, with barbs on their surface. Due to this barbed structure, they only move in one direction after penetration and do not fall off naturally. Microscopic expansion and contraction of tissues due to body temperature, along with mechanical forces from eyelid and eye movements, gradually push the setae deeper into the eye.
Setae from moth cocoons also have a similar barbed structure and cause intraocular inflammation equivalent to that from larval setae 5).
Inflammation in ocular tissues involves a complex interplay of three mechanisms.
Setae can migrate stepwise from the conjunctiva to the cornea, from the cornea to the anterior chamber, and from the anterior chamber through the iris and ciliary body to the vitreous. This migration occurs over a period of weeks to months4)5).
Zou et al. (2025) reported that tussock moth cocoon setae caused vitreous hemorrhage and tractional retinal detachment 13 months after injury. The lesion, initially Type III, progressed to Type V, representing the most severe course5).
Ashkenazy et al. (2022) evaluated a Type V moth setae case using an integrated approach with AS-OCT, B-scan, FA, fundus autofluorescence, and SD-OCT. A 45-year-old male maintained visual acuity of 20/25 and avoided vitrectomy with only two weeks of high-dose oral prednisolone1). Multimodal imaging enables non-invasive follow-up and is expected to improve the accuracy of surgical indication decisions.
Zou et al. (2025) performed staged procedures for a most severe case (vitreous hemorrhage + tractional retinal detachment) caused by cocoon setae: vitrectomy + intraocular foreign body removal + endolaser + C3F8 gas tamponade, followed by lens extraction + intraocular lens implantation + YAG laser posterior capsulotomy. Final visual acuity recovered to 20/20, reported as a case of complete recovery from the most severe outcome5).
Tamilarsan et al. (2022) reported four cases of Ophthalmia Nodosa in motorcycle riders, showing that insect collisions during high-speed riding are an occupational risk. The importance of prevention through wearing protective glasses or visors is emphasized 2).
