<prompt> A 32-year old male presents with unilateral diminished vision in the right eye. On examination, there is mild iritis, vitretis and a focal necrotic lesion is seen at the macula. The most likely diagnosis is:Multiple Evanescent White Dot syndromeOcular toxoplasmosisMultifocal chorioditisOcular sarcoidosis  <response>: Ans. b. Ocular toxoplasmosis Ref: Parsons 21e p242-43; Kanski 7e p429-30, 457-63; Yanoff Ducker 3e p828-30, 785; Harrison 19e 40e-6f 1400, 1402, 1404, 18e p229, 1724, 1726A 32-year-old male presents with unilateral diminished vision in the right eye. On examination, there is mild iritis, vitretis and a focal necrotic lesion is seen at the macula. The most likely diagnosis is ocular toxoplasmosis.Ocular toxoplasmosis presents with localized necrotizing chorioretinitis involving macula, satellite lesions, spill over granular anterior uveitis, vitritis leading to head light in fog appearance with floaters due to vitritis, diminished vision, pain, redness and photophobia in young adultsinfants.Ocular ToxoplasmosisToxoplasmosis is one of the most frequently identifiable causes of uveitis worldwide.MC cause of infectious posterior uveitis in non-immunocompromised individualsQ2nd MC cause of infectious posterior uveitis in patients with HIVAIDS MC cause: CMV retinitisQIt usually presents in infants or adults of 10-35 yearsQ.Clinical Features:Depends on patient age, location, size and severity of retinochoroiditis.Ocular manifestations include floaters and blurred vision.Decreased visual acuity may occur as a result of macular involvement or severe vitreous inflammation.Ocular toxoplasmosis presents withNecrotizing chorioretinitis destroying choroid and retina producing punched out heavily pigmented macular scarQSatellite lesion solitary inflammatory focus near old pigmented scarSpill over anterior uveitis may be granular resembling Fuchs syndromeSevere vitritis so dense as to prohibit an adequate view of posterior segment i.e. head light in fog appearanceQ.Bilateral macular involvement is common in immunocompromised.Triad of congenital toxoplasmosis: Convulsion Chorioretinitis Intraeranial calcificationQDiagnosis:Diagnosis of ocular toxoplasmosis is often made by clinical features.Diagnostic tests include demonstration of parasite. Sabin-Feldman dye test serological test require live T. gondii organism with a titer 1:16, complement fixation test, indirect hemagglutination test and ELISA for IgG and IgM.Treatment:MC treatment for ocular toxoplasmosis classic therapy: Pyrimethamine and sulfadiazine plus corticosteroidsQ.Alternative treatment: Quadruple drug therapy classic regimen plus clindamycin, as well as single or combined use of clindamycin, trimethoprimsulfamethoxazole, spiramycin, minocycline, azithromycin, atovaquone and clarithromycin. 