Astigmatism may be corrected with eyeglasses, contact lenses, or refractive surgery. Management can occur with eyeglasses, contact lenses, or surgery. Near-sightedness can be corrected with eyeglasses, contact lenses, or surgery. This feature is especially useful with long telephoto lenses. New techniques such as telephoto lenses and cameras mounted on tracks were employed. This is especially the case with longer telephoto lenses. All types of fisheye lenses bend straight lines. Some camera makers design lenses but outsource manufacture. Specific uses include cartilage replacements, contact lenses, and eye drops. These risks should be weighed against those of wearing spectacles or contact lenses. Accommodation is similar to the focusing of a photographic camera via movement of its lenses. This control is found on most EF zoom lenses. This mount is used for attaching filters to EF lenses. O and O represent the centers of symmetry of the two cameras lenses. This feature is found on most longer focal length lenses, and macro lenses.