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.
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,
The clinical photo below shows healed retinochoroiditis after two months of treatment with antimicrobial agents and oral steroids.