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Photos courtesy of: Mamta Agarwal, Sankara Nethralaya, India Used with permission. Not to be reproduced.

A 21-year-old man presented with complaints of gradual diminution of vision and floaters in the left eye for one month. This is the first time he experienced these symptoms and there was no history of any systemic illness. Currently, he was taking oral steroids (Prednisolone 20 mg/day), calcium supplements, and antacids. His best corrected visual acuity was 6/6 in the right eye and counts fingers at 1 meter in the left eye. The right eye was within normal limits. Slit lamp biomicroscopy in the left eye showed anterior chamber cells 1+, flare 1+ and vitreous cells 2+. Fundus examination of the left eye was as shown above.

1.	What is the most likely clinical diagnosis?
	b -- toxoplasmosis The fundus photo shows a yellowish white lesion in the macula adjacent to a pigmented scar associated with overlying vitreous haze, classically described as a "headlight in the fog" appearance.  Toxoplasmosis is the most common cause of posterior uveitis and accounts for nearly 90% of focal necrotizing retinitis. Toxocarisis usually occurs in children and is typically unilateral. It may present as a macular granuloma (elevated white lesion), peripheral granuloma with a tractional band extending to the disc, or endophthalmitis. Chorioretinal scars are not typically seen. Sarcoidosis occurs in the 20 – 50 year age group. Clinical features include granulomatous anterior uveitis, vitritis, periphlebitis ( candle wax dripping), choroidal granuloma, and cystoid macular edema. Systemic findings may include tachypnoea, facial nerve palsy, enlargement of salivary or parotid glands, hilar lymphadenopathy, erythema nodosum, and arthritis. Viral retinitis is caused by Herpes simplex virus, Varicella zoster virus, or rarely   cytomegalovirus. It can be associated with occlusive vasculitis, intra retinal hemorrhages, and vitritis. Chorioretinal scars are absent. There may be a history of chicken pox or herpes zoster in the past.
2.	What is the recommended treatment?
	c -- antimicrobial agents (pyrimethamine, sulphadiazine, clindamycin) and oral steroids Criteria  for  treatment includes the following: Lesion affecting the macula or optic disc Lesion threatening  a large retinal vessel or within the temporal arcade Severe vitritis causing two line drop in vision Any lesion in an immuno-compromised patient Classic first line therapy Pyrimethamine:     Loading dose – 100 mg/day                             Maintainence dose – 25 mg/day x 6-8 weeks Folinic acid:           5-20 mg/day Sulfadiazine:          Loading dose – 2g                             Maintainence dose – 1g every 6 hours  for 6-8 weeks Steroids:               40 -60 mg/day (only beginning 24 – 48 hrs after                             initiating antimicrobial therapy) Other antibiotics:   Clindamycin, azithromycin, atovaquone,                              trimethoprim/sulfamethoxazole The clinical photo below shows healed retinochoroiditis after two months of treatment with antimicrobial agents and oral steroids.