Used for simple operations like lumpectomies and lens implants, the centers achieve efficiencies impossible in a hospital, said Mr. Gordon of Morgan Stanley.

Half the people in the United States with lens implants have problems with them, a Government survey has found.

For lens implants, the most common problem was cloudy or blurred vision, and for pacemakers it was irregular heartbeat.

Most reported cases involve patients with compromised immune systems, indwelling foreign devices, or intraocular lens implants.

The projects have contributed directly and indirectly to advances made in areas like lens implants, the preservation of donated corneas, laser techniques and treatments to slow glaucoma.

Other types of surgery for nearsightedness include radial keratotomy, corneal ring implants, and intraocular lens implants.

And lens implants, routinely used for people already undergoing cataract surgery, can provide correction both near and distant, freeing them from wearing glasses.

New FDA-approved multifocal intraocular lens implants allow most post operative cataract patients the advantage of glass-free vision.

The number of cataract operations rose 50 percent, for example, and the price per operation went up 61 percent as more operations included lens implants.

Lenticular eyeglass lenses have been employed to correct extreme hypermetropia (farsightedness), a condition often created by cataract surgery when lens implants are not possible.