The macula lutea of anesthetized Rhesus monkeys were exposed to graded amounts of light emitted by a Q-switched ruby laser in order to determine the radiation threshold for retinal injury. The eyes were studied ophthalmoscopically and by means of flat preparations of the retinal pigment epithelium. Ophthalmoscopically visible lesions were observed at retinal energy densities of 0.07 joule (J)/sq cm and over. Histologic lesions of the retinal pigment epithelium were noted at retinal energy density levels as low as 0.01 J/sq cm.
Leibowitz HM, Peacock GR, Knox F, Friedman E. The Retinal Pigment EpitheliumRadiation Thresholds Associated With the Q-switched Ruby Laser. Arch Ophthalmol. 1969;82(3):332-338. doi:10.1001/archopht.1969.00990020334007