Case Studies:

A Case of T. californiensis
From Ophthalamic Surgery and Lasers 1996:

“A 51-year-old man presented . . . complaining of a red right eye. . . He had experienced a moderate amount of mucous discharge during the previous 4 days, which had increased significantly on the last day. The patient had worn contacts until the day before the examination. An examination of the right eye revealed a 1+ bulbar conjunctival injection. Mucous-like strands, which swirled away on eversion of the lower lid, were evident in the inferior fornix of the eye. Irrigation and a cotton-tipped applicator were used to remove five slender white worms approximately 1 inch long. The remainder of the examination was unremarkable. Tobrex ophthalamic solution was prescribed and the worms were submitted for pathologic identification. During a follow-up visit the next day, a sixth worm was removed from the inferior fornix of the same eye. The patients symptoms resolved soon thereafter with no recurrences.
“This patient is a resident of Utah and did not spend any time in California within 2 months prior to the discovery of the worm. Additional history was obtained from the patient after identification of the worm. The patient is an avid hiker and frequents the Utah wilderness. One week prior to the clinical examination, he had hiked in the Wasatch Mountains near Salt Lake City. Three to four weeks before presentation he had hiked in the backcountry of Zion National Park in southern Utah, and 8 weeks prior to the discovery of the worms he spent time in the La Sal Mountains of southern Utah. The patient has an interest in wild animal feces and recalled handling some on the latter two occations. He also owns two German shorthaired dogs and handles them often. The patient did not recall and instance where a fly lodged in his eye during any of the excursions.”

An interesting case of intraocular infestation with T. callipaeda
British Journal of Ophthalmology, 1999

“ A 21 year old Chinese woman presented to the ophthalmology department at Shanton Central Hospital, Guangdong, China, complaining of decreased vision in her right eye and a floater in the right visual field. She had no photopsia or field loss, and no pain, redness, or discharge. She had no past ocular history, and was otherwise well.
“On examination she had a visual acuity of 6/60 in the right eye and 6/6 in the left eye. There was no external evidence of trauma; the lids were healthy, the conjunctiva white, the cornea clear, and the anterior chamber quiet. A mild vitreous haze obscured the foveal reflex, and clearly visible within the vitreous cavity was a live, mobile, white worm. There was no retinal abnormality.
“One month later she underwent a three port pars plana vitrectomy, and the worm was coaxed into a flute needle and removed intact. The patient made an uncomplicated recovery from surgery. At 6 weeks postoperatively the eye was quiet and she had a visual acuity of 6/24. On detailed examination, the worm was identified as an adult female specimen of Thelazia callipaeda . . . in the absence of preoperative and postoperative symptoms of inflammation due to infestation, pharmacological treatment was not commenced in this case.”
Of note, the authors put forward the suggestion that humans are in fact the definitive host for T. callipaeda. For intraocular colonization, they propose, the infective stage is likely filariform larva, with the portal of entry being the skin. An alternate mode of entry suggested is oral: the larva or embryonated egg ingested with raw drinking water.