The HF A is a computerized perimeter with a very comprehensive set of test point patterns, strategies and custom tests. The instrument employs several solutions which have proved useful in earlier computerized perimeters and several new concepts. The construction with stimulus generation through a projection system, input through a CRT, programmes stored in PROMs and a double disc drive for storage of test results makes it simple to adapt the instrument to future needs, whether these are new test algorithms or point patterns, different input or display screens or new statistical analysis programmes. All these changes could be made without modification of actual instrument hardware. REFERENCES 1. Dannheim, F. and Drance, S.M. Psycho visual disturbances in glaucoma. A study of temporal and spatial summation. Arch. Ophthalmol. 91: 463 -468 (1974). 2. Fankhauser, F. and Hiiberlin, H. Dynamic range and stray light. An estimate of the falsifying effect of stray light in perimetry. Documenta Ophthalmol. 50: 143-167 (1980). 3. Fankhauser, F., Hiiberlin, H. and Jenni, A. Octopus programs SAPRO and F. Two new principles for the analyses of the visual field. Graefes Arch. Klin. exp Ophthal- mo1216: 155-165 (1981). 4. Gramer, E. and Krieglstein, G.K. Zur Spezifitiit der iiberschwelligen Computer- perimetrie. Klin. Mbl. Augenheilk. 181; 373-375 (1982). 5. Gramer, E., Kontic, D. and Krieglstein, G.K. Die computerperimetrische Dar- stellung glaukomatoser Gesichtsfelddefekte in Abhangigkeit von der Stimulus- grosse. Ophthalmologica 183: 162-167 (1981).