CMV retinitis in HIV occurs when the CD4 counts fall below which of the following levels?

CMV Retinitis is the most common cause of loss of vision in AIDS patients. Majority of cases of CMV retinitis occur in patients with a CD4+ T cell count <50/micro L. Therefore, patients at high risk of CMV retinitis (CD4+ T cell count <100/micro L) should undergo an ophthalmologic examination every 3-6 months. CMV retinitis usually presents as a painless, progressive loss of vision. Patients may also complain of blurred vision, floaters and scintillations. It is usually bilateral. The characteristic retinal appearance is presence of perivascular hemorrhage and exudate. Treatment consists of oral valacyclovir, ganciclovir, IV ganciclovir, or IV foscarnet, with cidofovir as an alternative. Ref: Textbook of Microbiology By Ananthanarayan and Panicker, 8th Edition, Page 573 ; Harrison's Principles of Internal Medicine, 18th Edition, Chapter 189