Threshold retinal burns are produced in the rhesus monkey by a helium-neon (He-Ne) continuous wave (CW) laser. The lowest power to produce a minimal thermal lesion was 7 milliwatts for an unfocussed raw beam.
Ham WT, Geeraets WJ, Mueller HA, Williams RC, Clarke AM, Cleary SF. Retinal Burn Thresholds for the Helium-Neon Laser in the Rhesus Monkey. Arch Ophthalmol. 1970;84(6):797-809. doi:10.1001/archopht.1970.00990040799021