The toxoplasmosis infection can sometimes spread to the eyes. This is called ocular toxoplasmosis.
Ocular toxoplasmosis
The Toxoplasma gondii (T. gondii) parasite, which causes toxoplasmosis, can lie dormant (inactive) in the retina for many years. The retina is the light-sensitive layer of tissue at the back of the eye. However, if the parasite becomes active again it can start a new infection.
Ocular toxoplasmosis causes ocular lesions, which are wounds in the eyes caused by inflammation and scarring. These can appear in the:
- retina - the nerve tissue that lines the back of the eye
- choroid - the layer behind the retina that contains major blood vessels
This damage to the eyes is called retinochoroiditis and it can cause eye problems such as:
- partial loss of eyesight in one eye
- squint - where one eye looks in a slightly different direction to the other one
- clouding of the eye’s lens (cataracts)
- eye shrinking (microphthalmia)
- loss of cells and tissue from the optic nerve, which connects the eye to the brain, resulting in poor vision (optic atrophy)
Antibiotics and steroids are often used to treat the lesions. The scarring that is caused by toxoplasmosis will not clear up, but treatment may prevent it from getting worse.
If the infection keeps returning, long-term antibiotics may be prescribed. While this may help to prevent the infection from reoccurring, the long-term side effects of these medications are not yet known.
Congenital toxoplasmosis
In most cases, babies born with congenital toxoplasmosis develop normally after treatment with antibiotics.
However, in up to 4% of cases, serious complications can develop within the first years of life. These include:
- permanent visual impairment (partial or, very rarely, complete sight loss)
- permanent brain damage
Retinochoroiditis is a common complication of congenital toxoplasmosis. The risk of retinochoroiditis occurring is around 10% in infants who are born with congenital toxoplasmosis.
One study found that 18% of children with congenital toxoplasmosis had at least one ocular lesion as a result of retinochoroiditis. Of these children, 42% developed a second ocular lesion.
Cases of ocular toxoplasmosis can also occur years later. For example, one study that looked at cases of congenital ocular toxoplasmosis found that the average age at which it appeared was nine years old.
It is also possible for someone to develop complications when they are in their twenties or thirties. These may include:
More research is still needed in following up cases of congenital toxoplasmosis. Regular eye tests may help detect any abnormalities as they develop and treatment with antibiotics can limit the damage toxoplasmosis causes. However, at present, it is not possible to reverse any damage that has already been done.
