| Description | This is a visual field test object in a case, donated by Prof. Oliver FitzGerald. The case is a rectangular black faux leather-covered box, composed of two hinged parts locked together by buttons. Inside, the case features a blue velvet lining where 19 different-sized and coloured disks are held, and a long black metal shaft (called a wand) featuring two fenestrated ends is secured. The lid, covered in blue silk, features gold ink writings: "Theodore Hamblin Ltd Dispensing Opticians London W.1". The shaft of the wand features in gold: "Hamblin London". The disks are called testing objects, and they are lined in the case based on their size and colour as follows: green, red, white (the first nine), then blue for a total of 19. They can be secured into the fenestration by screwing them in.
The test, also known as the tangent screen test, is a method used to evaluate the visual field, particularly the central and peripheral vision. The test involves a flat, usually black, screen with a central fixation point. The patient sits a specific distance from the screen, typically one meter. The examiner uses the wand with the testing objects to present visual stimuli at various locations on the screen. The patient is asked to fixate on the central point and indicate when they can see the disk. This test helps in detecting blind spots (scotomas) and assessing the extent of the visual field. It is still used for diagnosing conditions like glaucoma, optic neuritis, and other neurological disorders affecting vision. The results are plotted on a chart, showing areas where the patient has normal vision and areas where vision is impaired. |