SPECIAL OPTICAL AIDS FOR THE PARTIALLY SIGHTED *

Within the past decade an increasing activity has been noted within the field of visual rehabilitation by high-power unconventional optical aids. The visual rehahilitation for reading thus obtained so far greatly surpasses previous expectations. A fairly comprehensive literature is already available on the subject. Reference may be made particularly to books and papers by Bier, Feinbloom, Fonda, Kestenbaum, Pameijer, Louise Sloan, Stinison and others. Loss of reading vision is a serious handicap to the partially sighted. This can, however, be remedied to a certain extent, because a book or a newspaper normally can be held close to the eyes. The partially sighted will then have a chance of obtaining large and, with convex lenses in front of the eye, also clear retinal images of the letters. In some cases even persons with visual acuities down to 1/60 can, in fact, be aided to seeing the letters of ordinary printed matter. Reading presupposes that the patients can accept a very short reading dis. tance, and consequently a greatly limited field of vision for reading. The normal saccadic reading movements of the eyes must be replaced by small, often irregular movements: scanning. The patient must as a rule accept monocular vision. A quite new reading technique will t hus have to be practised. This will most often demand an educational, stimulating effort from both the ophthalmologist and the optician. For intermediate distances it is more difficult to help the partially sighted with high-power optical aids. Many working processes require a fixed working distance of about 40 cm and a large field of vision. The very low-acuity patient cannot be rehabilitated to these working conditions by means of special optical aids. Where modifications are