4R—Rifampicin for 4 months is an alternative for those who are unable to take isoniazid or who have had known exposure to isoniazid-resistant TB. 3HR—Isoniazid and rifampicin may be given for 3 months. 2RZ—The 2-month regimen of rifampicin and pyrazinamide is no longer recommended for treatment of LTBI because of the greatly increased risk of drug-induced hepatitis and death. 3RPT/INH - 3-month (12-dose) regimen of weekly rifapentine and isoniazid.Evidence for treatment effectiveness:
A 2000 Cochran review containing 11 double-blinded, randomized control trials and 73,375 patients examined six and 12 month courses of isoniazid (INH) for treatment of latent tuberculosis. HIV positive and patients currently or previously treated for tuberculosis were excluded. The main result was a relative risk (RR) of 0.40 (95% confidence interval (CI) 0.31 to 0.52) for development of active tuberculosis over two years or longer for patients treated with INH, with no significant difference between treatment courses of six or 12 months (RR 0.44, 95% CI 0.27 to 0.73 for six months, and 0.38, 95% CI 0.28 to 0.50 for 12 months).A 2013 systematic review published by the Cochrane Collaboration, compared Rifamycins (monotheraphy and combination therapy) to INH monotheraphy as an alternative in preventing active TB in HIV negative populations. The evidence suggested that shorter Rifampicin regimes (3 or 4 months) had higher treatment completion rates and fewer adverse events when compared to INH. However, the overall quality of evidence as per GRADE criteria was low to moderate.
Radiation retinopathy is damage to retina due to exposure to ionizing radiation. Radiation retinopathy has a delayed onset, typically after months or years of radiation, and is slowly progressive. In general, radiation retinopathy is seen around 18 months after treatment with external-beam radiation and with brachytherapy. The time of onset of radiation retinopathy is between 6 months to 3 years.An exposure to doses of 30-35 grays (Gy) or more is usually required to induce clinical symptoms, however, retinopathy may develop after as little as 15 Gy of external-beam radiation. A reported safe dose is 30 Gy (3,000 rad): 10 Gy (1,000 rad) per week in five fractions of 2 Gy (200 rad). Signs and symptoms
Clinically, affected people may not have symptoms or may complain of decreased visual acuity. Ophthalmic examination may reveal signs of retinal vascular disease, including cotton-wool spots, retinal bleeds, microaneurysms, perivascular sheathing, capillary telangiectasis, macular edema, and disc edema. Capillary non perfusion, documented by fluorescein angiography, is commonly present, and extensive retinal ischemia can lead to neovascularization of the retina, iris, and disc. Staging of radiation retinopathy has been proposed. Pathophysiology
Radiation retinopathy is very similar to other vascular diseases. Diabetes and radiation primarily damage the retinal capillaries. Diabetes results in early loss of pericytes and thickening of the basement membrane. Radiation however, damages the endothelial cells. Diagnosis
Treatment
The management of radiation retinopathy is similar to that for diabetic retinopathy and includes focal laser therapy to reduce macular edema or panretinal photocoagulation to treat zones of ischemia and neovascularization.