A 40-year-old lady had a history of inadvertent binocular injury while using a towel infested with caterpillar setae, 12 years back. She was treated for removal of hair from the ocular surface, the same day of injury, elsewhere. Apparently, several setae were removed and repeated examination did not reveal any residual hair in the eyes. No documented details were available with the patient. She presented to us with redness, pain and decreased vision in the left eye, since three years. She was being treated for intermediate uveitis with oral and topical steroids during the same period. Her general and systemic examinations were normal. Best corrected visual acuity (BCVA) in right eye was 20/30 and 20/2000 (CF 2 feet) in the left. Slit-lamp biomicroscopy of the right eye revealed mild anterior chamber (AC) reaction and a fine intralenticular caterpillar hair in the superior quadrant of the lens with early nucleus sclerosis [Figure 1]. Left eye examination revealed 2+ cells and flare in AC, 2+ vitreous cells, a point anterior (lens) capsule rupture in the nasal quadrant with impacted caterpillar hair and a rosette-shaped cataractous lens [Figure 2]. Intraocular pressure and iridocorneal angles of both eyes were normal. Right eye fundus was normal except for pars plana exudates. Left fundus revealed vitreous haze, sclerosed retinal vessels in superotemporal quadrant and pars plana exudates inferiorly. Ultrasound Biomicroscopy (UBM) did not reveal any more intraocular setae. Patient was treated with oral steroids, posterior subtenon triamcinolone (40 mg) injection, topical steroids and cycloplegics in both eyes. At six weeks follow-up, visual acuity was maintained in both eyes while the inflammation had subsided. The patient underwent left eye phacoemulsification, caterpillar hair removal, (acrylic foldable) intraocular lens (IOL) implantation ′in the bag′ and a number 240 silicone band encirclage under systemic steroid cover. Pars plana vitrectomy was deferred as preoperative UBM and peroperative fundus examination did not reveal any more setae. At six weeks follow-up, BCVA in the left eye was 20/200 with 1+ cells in the AC and a stable IOL. Oral and topical steroids were tapered. At one year follow-up, left eye was quiet and visual acuity was maintained; improvement being limited by chronic cystoid macular changes. Optical coherence tomography revealed increased macular thickness with multiple intraretinal cystoid spaces [Figure 3].
Caterpillar setae-incited inflammatory reaction has been classified into five types:1 Type 1: An acute reaction to the hair consisting of chemosis and inflammation. This begins immediately and lasts for some weeks. Type 2: Chronic mechanical keratoconjunctivitis caused by hair lodged in the bulbar or palpebral conjunctiva. Foreign body sensation occurs and linear corneal abrasions are seen. Type 3: Formation of grey-yellow nodules in the conjunctiva (granulomas). Setae may be subconjunctival or intracorneal and may be asymptomatic. Type 4: Iritis secondary to hair penetration of anterior segment. Type 5: Vitreoretinal involvement (10-20%) after hair penetrate the posterior segment via the anterior chamber or transsclerally. This may occur some years later and effects can range from mild vitritis with or without cystoid macular edema to a frank endophthalmitis. Pathophysiology of inflammation is assumed to be both partially mechanical2 (progression caused by distal end oriented barbs on setae) and partly toxic2-4 (thymetopoien secreted from the venum gland connected to the hair shaft). A number of theories have been postulated suggesting possible mechanism of migration of setae.5,6 Gunderson et al.,5 suggest that because the setae have no propulsive power of their own, movements of the globe with versions, respirations and pulse together with the constant iris movement propel the spines (on the setae) forward. It can be seen from the electron micrographs that the direction of the spines is vital in this, allowing only forward movements. Ascher6 suggested that it was the inflammatory exudates pushing against the broken end of the hair that allowed it to move along the path of least resistance. A further factor that determines the depth of penetration is the initial injury. None of the previous literature have reported intralenticular migration of setae and the same can be incorporated in the above classification proposed by Cadera et al. 1 The lens capsule might possibly pose resistance to intralenticular migration of setae explaining this extremely uncommon presentation. Complete intralenticular entrapment of the setae in the right eye of this patient might have enclosed the toxins within a closed compartment resulting in a blunted inflammatory response. Partial intralenticular penetration of setae in the left eye might have exposed toxins to intraocular milieu allowing a more pronounced inflammatory response. This case indicates the value of a careful examination and history-taking in a case of uveitis which allows for accurate diagnosis and treatment. Phacoemulsification with steroid cover and periodic follow- up in the management of cataractous lens associated with intralenticular setae is of potential value in such eyes.
Dr Jyotirmay Biswas for technical help.
1. Cadera W, Pachtman MA, Fountain JA, Ellis FD, Wilson FM 2nd. Ocular lesions caused by caterpillar hairs (ophthalmia nodosa) Can J Ophthalmol. 1984;19:40–4
2. Steele C, Lucas DR, Ridgway AE. Endophthalmitis due to caterpillar setae: Surgical removal and electron microscopic appearance of the setae Br J Ophthalmol. 1984;68:284–8
3. Lamy M, Pastureaud MH, Novak F, Ducombs G, Vincendeau P, Maleville J, et al Thaumetopoein: An urticating protein from the hairs and integument of the pine processionary caterpillar (Thaumetopoea pityocampa Schiff, Lepidoptera, Thaumetopoeidae) Toxicon. 1986;24:347–56
4. Horng CT, Chou PI, Liang JB. Caterpillar setae in the deep cornea and anterior chamber Am J Ophthalmol. 2000;129:384–5
5. Gundersen T, Heath P, Garron LK. Ophthalmia nodosa Trans Am Ophthalmol Soc. 1951:151–69
6. Ascher KW. Mechanism of locomotion observed on caterpillar hairs Br J Ophthalmol. 1968;52:210