Multiple cases of acquired toxoplasmosis retinitis presenting in an outbreak.

OBJECTIVE: The purpose of the study was to examine the variability in presentation and outcome of individuals presenting with acquired toxoplasmosis retinitis in the setting of an outbreak of the disease. DESIGN: The study design was a case series. PARTICIPANTS: Twenty-one eyes of 20 patients with equal gender distribution and a mean age of 54 years followed for 38 to 170 weeks (mean 113.7 weeks) were studied. INTERVENTION: Systemic antimicrobials and corticosteroids when indicated were given. MAIN OUTCOME MEASURES: Visual acuity, media inflammation and clarity, resolution of active retinitis, and appearance of recurrence were observed. RESULTS: Fifteen of 21 lesions were active, and 7 of the total number of lesions fell within the macula-peripapillary region. Overall, vision improved with treatment except in cases of macular involvement (3 cases) and persistent vitritis (3 cases). Four recurrences have occurred to date. CONCLUSIONS: This is the largest reported outbreak of acquired toxoplasmosis retinitis occurring within a single outbreak. Twenty-one eyes of 20 patients presented with retinal lesions, and on average, those treated for active retinitis had improvement in vision.

Experiments on the absorption of argon and krypton laser by blood.

Experiments were performed to determine the absorption by and transmission through blood of argon blue-green (ABG) and green (AG) and krypton red (KR) laser light. Krypton was transmitted better through intact erythrocytes than argon. The difference between krypton and argon was greater if the erythrocytes contained oxygenated hemoglobin (Hb) than deoxygenated Hb. None of the wavelengths penetrated well a confluent blood specimen only 4 cells thick. Branch retinal vein occlusions were created in monkeys causing scattered areas of retinal hemorrhage. Argon burns placed in areas of retinal hemorrhage caused much inner or full thickness retinal damage. Krypton passed through the inner retinal hemorrhage without causing damage and created a burn at the level of the retinal pigment epithelium and inner choroid. Preretinal hemorrhages were created in rabbits by perforating Bruch's membrane with a high intensity krypton burn. Argon burns placed over the preretinal hemorrhages were absorbed much more than krypton burns. Neither argon or krypton however could penetrate even moderately thick preretinal hemorrhages to cause an underlying retinal burn.