Lesion in the left eye.

a. What is the most likely diagnosis.

Answer
Reactivation of toxoplasma chorioretinitis.

The picture shows fluffy white lesions at the edge of a scar.

The presence of the chorioretinal scar indicates previous
toxoplasma infection and this may be prenatal or postnatal.

b. Name two ways in which this lesion may be acquired.

Answer
Congenital from mother acquiring the infection during pregnancy.
Acquired through ingestion of oocytes or bradyzoites from cat faeces or undercooked meat.
Rarely the infection may be acquired through transfusion of white blood cells or organ transplant.

AnswerA cyst of Toxoplasma gondii.

d. Name four circumstances in which systemic treatment is indicated.

Answer
Severe vitritis affecting the vision.
Location of the lesion in the papillomacular bundle or optic nerve.
Lesion in the major retinal vessels (due to risk of retinal artery occlusion).
Immunocompromised patients.

e. Name four antibiotics which may be given for this condition.

Answer
Any of the following can be used:
Clindaycin
Sulfadizine
Pyrimethamine
Trimethoprim
Azithromycin
Atovaquone

Antibiotic treatment reduces the duration and severity of symptoms of acute intraocular inflammation and the risk of permanent visual impairment. Adjunctive therapy with 

corticosteroids is often used to diminish the duration and 
severity of the inflammatory symptoms. The antibiotics are ineffective against the cysts but stop the multiplication of tachyzoites during episodes of active retinochoroiditis.