Abstract: A laser photocoagulator 10, comprises a fibre optic guide 13 one end of which is accommodated by an endoscope 14 and the other end of which has a coupling 18 for connection to a laser 11 and a gas supply 12. Launch optics 32 are accurately located in coupling 18 with respect to end 34A of optical fibre 34 which traverses the length of the guide 13 thereby rendering the guide replaceable without dislocation of the endoscope 14, the laser 11 and the gas supply 12. The coupling 18 comprises separate clamp means for the optical fibre 34 and the optics 32 enabling accurate alignment co-axially and spatially so that the laser output is focussed on the free end 34A of the fibre 34 without any requirement to align the laser 11 accurately with optics 32.