The development of a thin stainless steel ophthalmic applicator is described. The features of this device are that it can be assembled with the radioactive sources (I-125) precisely positioned without the use of adhesives or mechanical devices such as clamps or screws in a matter of a few minutes under sterile conditions. Dismantling occurs in seconds after which the applicator is ready for cleaning and re-sterilisation. The radioactive sources are contained in an acrylic button which fits neatly into a stainless steel shell 1 mm thick. Different distributions of sources may be accommodated in the same stainless steel shell by inserting a different acrylic button. The overall thickness of the plaque is 2.6 mm but potentially can be reduced to 2.1 mm. Suture holes are provided on a flange subtending 120 degrees around the circumference of the shell and are exactly matched on a stainless steel template. An analysis of the dosimetry suggests that the treatment of the radioactive I-125 seeds as point sources may lead to only small errors in the determination of dose at the scleral surface and tumour apex. The differences in the dosimetry resulting from the treatment of the seeds as line sources appear to be of little consequence. As a result, point source dosimetry with anisotropy factor removed is quite satisfactory.