Image supplied by Gerard McCarron, Specsavers Cessnock, NSW
The photograph above shows ophthalmic parasitosis with tractional fibrosis extending from the lesion to the optic nerve, causing distortion of the epi-retinal layer. Inactive peripheral retinal focal lesions can also be seen in the inferior segment adjacent to the major arterial arcade.
Patients with ophthalmic parasitosis may present with varying clinical symptoms. As parasitic infection results in inflammation of one or more ocular structures, most patients exhibit signs that mimic inflammatory conditions of the eye such as conjunctivitis, keratitis, or uveitis. This is usually accompanied by symptoms of reduced vision. Therefore, a thorough examination of the eye with dilation is important.
On retinal examination, some posterior ocular signs associated with parasitic infection of the eye are:
- Choroiditis (focal lesions)
- Retinal vasculitis
- Retinal haemorrhages
- Optic atrophy
- Retinal detachments
- Orbital cysts.
A thorough history can also highlight risk factors for parasitic infection. It is important that the optometrist obtains information that may lead to a diagnosis of exclusion, such as whether the patient has travelled in an endemic area, what kind of systemic symptoms they are experiencing, and other risk factors.
Depending on the level of ocular involvement, these infectious changes can cause damage to ocular tissues and vision loss.
Ophthalmic parasitosis is a broad term used to describe parasitic infection of the eye. Parasitic infection can affect any part of the eye and can occur due to direct infection by the parasite or indirect infection through an immune-response triggered by the infection or contact with contaminated products (trauma or surgery).
Toxoplasmosis and Acanthamoeba are both forms of parasitic infections observed by optometrists. There are also many other types of parasitic infection that can occur with ocular manifestations including but not limited to: toxocariasis (roundworm), malaria, giardiasis (water-borne), and onchocerciasis (insect-borne).
Progression & Prognosis
Prognosis for patients with ophthalmic parasitosis is improved the earlier the infection is detected and managed. Diagnosis is confirmed through different types of testing that may include: microscopy, biopsy, serological or urine tests, or histological examination.
Ophthalmological treatment will depend on the type of infection and may include surgical removal or treatment with anti-parasitic medication. Occasionally, a steroid treatment may be deemed appropriate to suppress the inflammatory response.
Optometrists should be alert to the possibility of a parasitic cause for ocular inflammatory conditions, take a careful history, and refer a patient on for further testing urgently if ophthalmic parasitosis is suspected.