Every step of the work requires unusual care to avoid damage to product and equipment. Ophthalmic Technicians make lenses to correct faulty vision. They read doctor's prescriptions and fabricate lenses according to specifications that may include a combination of corrections. They place the lens in an automatic lens grinder and set the required time. Finally, a polishing machine with a fine abrasive polishes the lens to a smooth, bright finish.
Technicians assemble the lenses with frames to produce finished eye glasses.
The equipment and procedures used in both ophthalmic and optical work are similar. Optical lens grinders, however, work with a greater variety of optical materials and usually must maintain greater optical and dimensional accuracy. Some elements must be accurate to a millionth of an inch and the process may take days or weeks and cost thousands of dollars. In contrast, ophthalmic lenses do not use as many types of exotic materials, and do not require as much time to make. Tolerances within a few thousandths of an inch usually are acceptable, although great care and skill are needed for grinding two or more corrections into a lens.