| 摘要 |
<p>The spectacles can be 'focussed' and are for use with small print and certain ocular exercises. The optical parts are placed in the position occupied by the normal lenses. They are opaque discs, each with holes of small diameter, of about 1 to 3.5 mm. Between them is a space slightly more than their diameter. The holes are made on horizontal lines, spaced at half an interval. The distances between the holes are the same in all directions. The perforated space extends to within 3 to 7 mm of the edges of the mounting.</p> |
