Introduction:
Infection of the eye or traumatic eye injuries due to a foreign body is a common problem. Almost 17 % to 40 % of penetrating eye injuries occur due to foreign bodies, and 3 % of these cases need emergency interventions.
Ophthalmia nodosa is defined as inflammation of the eye brought by the hair of certain insects or vegetable materials in various ocular tissues. It is also known as a nodular conjunctival reaction. Foreign bodies cause mechanical trauma to the ocular tissues, which leads to inflammatory reactions and toxins and virulent bodies present in the foreign particle responsible for allergic reactions. So, this is a combination of traumatic injury, anaphylactic or allergic reaction, and infectious condition.
Wagenmann, in 1890, called it pseudotuberculosis. In 1904, Saemisch renamed it and described it as granulomatous nodules found on the iris and conjunctiva. This disease has seasonal predilection and is predominantly seen in the coastal regions of the Eastern Mediterranean regions.
What Is the Cause?
Caterpillar mainly causes it (belonging to the order Lepidoptera Geserick) setae and hair, hair of the insects specifically tarantula, vegetable spores, or hairs, especially from the pine tree.
These hairs and spores are blown into the conjunctival fornices like a missile with the help of wind speed or rubbing action. In addition, barbs are present at an angulation of 30 degrees, which helps these foreign bodies penetrate further deeper into the tissue.
Initial trauma may cause redness and mild irritation. The redness and irritation are followed by a quiescent interval lasting for a few days or several months, presumably during which foreign material migrates through the cornea and outer eye. An intense inflammatory reaction and irritation of the eye follow it.
What Are the Signs and Symptoms?
Patients may complain of the following:
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Redness and enlargement of the eye.
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Pain in the eye.
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Foreign body sensation and itching.
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Photophobia.
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Increased lacrimation.
On examination, the following features are observed.
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Skin Urticaria: Redness and itching of the skin around the eye and eyelid.’
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Chronic Kerato-Conjunctivitis: Infection of cornea and conjunctiva, blurred vision, and purulent discharge.
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Corneal Granuloma: Presence of granulomatous tissue on the external surface of the eyelid or the palpebral conjunctiva.
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Punctate Chorioretinitis: Inflammation of choroid and retina.
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Cystoid Macular Edema: This is characterized by retinal thickening of the macula due to the destruction of the normal blood-retinal barrier.
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Papillitis: Inflammation or deterioration of a portion of the optic nerve.
What Is the Pathophysiology?
The pathophysiology event of this condition can be divided into two parts:
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Traumatic injury followed by chronic infection.
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An allergic reaction by toxins like thaumetopoeid. The allergic reaction is a type four hypersensitivity and is low-grade in nature.
The histopathological features will include infiltration of lymphatic cells, macrophages, and epithelioid cells encircled by a thick fibrous capsule. The prolonged and sustained infection leads to the formation of granuloma. In addition, the infection is characterized by forming giant cells and plasma cells with focal infiltration of lymphocytes.
What Are the Types?
Ophthalmia nodosa can be of five types according to signs and symptoms.
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Type 1: Acute anaphylactoid reaction to the hair, which begins immediately and lasts a few days, causing chemosis and inflammation.
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Type 2: Chronic mechanical keratoconjunctivitis is caused by hair lodged in the bulbar or palpebral conjunctiva and leads to linear corneal abrasions.
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Type 3: Grayish yellow granulomatous nodule formed in the conjunctiva, and the hair may be positioned subconjunctival or intracorneal. Patients may be asymptomatic in these cases.
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Type 4: Iritis, secondary to hair penetration into the anterior segment, may become severe with iris nodule formation and hypopyon. Setae may be subconjunctival or intracorneal and may be asymptomatic.
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Type 5: Vitreoretinal involvement after hair penetration into the posterior segment through the anterior chamber or transscleral route. The vitreoretinal involvement may occur early or some years later.
How to Diagnose It?
The most routine eye examination in this condition is a slit lamp examination, where ocular structures are observed under a low-powered microscope with the help of a light filter. However, the small size of the hairs makes it difficult to observe. Other diagnostic methods are:
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Scheimpflug Imaging: This device consists of a lens section and rotates around 180 degrees to produce an image of the anterior and posterior capsule.
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Optical Coherence Tomography (OCT): This method uses deep cross-sectional analysis of the ocular structure under reflected light.
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Ultrasound B-Scan: This method is a time-domain OCT (TD-OCT), forming a cross-sectional image of the eye structure.
According to the type of ophthalmic nodosa, the findings of the test may vary
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Type 1: In this type, conjunctival chemosis and injection are seen in the anterior chamber.
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Type 2: Prominent corneal epithelial defect with stromal infiltration.
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Type 3: Vertical abrasion of corneal tissue with lid eversion and presence of conjunctival nodules.
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Type 4: Presence of white cell layer in an anterior chamber known as hypopyon.
In the posterior segment following changes are seen:
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Pars planitis or infection of the uvae or middle layer of the eye.
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Macular edema.
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Yellow patches of retinochoroiditis.
What Are the Complications?
If not treated, this will lead to the following complications:
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Endophthalmitis: Purulent infection of vitreous and aqueous humor.
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Seasonal Hyperacute Panuveitis: This is a rare condition seen only in Nepal, and it is characterized by severe infection following the loss of vision.
How To Treat It?
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Removal of Hair: The hair is removed under topical anesthesia with the help of a 26G needle, followed by eye irrigation and the application of topical antibiotics. This treatment is helpful for Type 1 and Type 2 cases.
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Surgical Treatment: Removal of surgical nodules, vitrectomy, and hair disruption by applying Nd: YAG laser can be done in Type 3, 4, and 5 cases. In addition, topical steroids and antibiotics can also be prescribed for application. In severe cases, a vitrectomy ( surgery of the retina and vitreous) can also be done.
Conclusion:
Initial symptoms of ophthalmia nodosa are mild. However, if not treated timely, it may turn into serious complications. Modern diagnostic aids help detect such cases efficiently and cure them completely. Additionally, simple use of protective eye gear and glasses can be helpful to prevent such disorders.
