Patrick's Scotometer

Historical Significance: George Amigo writes (Aust J Optom 1961; 44(7) p331) 'The Patrick Direct Vision Scotometer represents a development which, it is felt, indicates the direction field screening instruments will take in future. This instrument combines the method of confrontation with scotometry of the central field. The patient fixates a green fixation point in an otherwise dark field. The examinerviews the same field from the opposite side and his view contains concentric circles in 5" steps and radial markings in 15 degree intervals as well as the outline of the average shape and position of the blind spot. A point source of light is provided at the end of a target holder, which is seen by both the patient and the examiner. The viewing distance corresponds to optical infinity and the actual size of the field is magnified 23 times by the eyepiece. The Patrick scotometer incorporates most of the desirable features of an instrument used for the exploration of the central field. It can be employed both as a preliminary screener and as a scotometer. It is compact, easy to apply, and relatively inexpensive. A few modifications and refinementscould however be suggested: 1. A second peripheral stimulus to enable simultaneous double stimulation. 2. Provision to alter the size of the stimulus by a system of variable apertures. 3. Interchangeable filters in front of the illumination system affording qualitative scotometry. 4. Provision for an on-off push button for intermittent stimulation. Yet even without these modifications this instrument is ideal for both screening and detailed testing of the central field. In the consulting room no time is wasted with the usual preparations, and since it is light and portable it can be used for bedridden patients also.'