An Incidentally Detected Synthetic Fiber Embedded in the Corneal Stroma: A Report of a Rare Case

Corneal foreign bodies (CFBs) are typically caused by the penetration of external materials such as metallic particles, concrete fragments, or plant matter into the corneal tissue and are usually accompanied by intense pain or a foreign-body sensation. We report an extremely rare case of an intrastromal CFB composed of synthetic fiber, which was discovered incidentally in an asymptomatic patient and confirmed histopathologically. A 54-year-old woman presented with bilateral visual impairment due to cataract. Slit-lamp examination revealed bilateral cataracts and a curved, white, linear foreign body approximately 1 mm in length embedded within the corneal stroma of the right eye. The patient had no history of ocular trauma or surgery. Review of anterior segment photographs taken five years earlier for dry eye evaluation demonstrated an identical finding in the same location, indicating that the lesion had been present for years without symptoms. The foreign body was removed under slit-lamp visualization using a 27-gauge needle and forceps. The extracted material was a slender filament lacking cellular components, consistent with a non-biological synthetic fiber. Following removal, the corneal opacity improved. A review of the literature identified reports of conjunctival granulomas or chronic inflammatory reactions caused by synthetic or cotton fibers, as well as intraocular penetration of fibers following ocular surgery or trauma; however, all previously reported cases were symptomatic. Synthetic fibers, commonly present in clothing and indoor environments, can adhere to the ocular surface and, in rare instances, penetrate into the corneal stroma even in the absence of trauma or symptoms. This case highlights a previously unrecognized route of fiber intrusion and suggests that synthetic fibers should be considered in the differential diagnosis of asymptomatic corneal opacities.