Tech Connection
Super Spectacles
Imagine the possibilities — eyeglasses that correct higher-order aberrations.
By Louis J. Catania, O.D., F.A.A.O.

IN MY LAST COLUMN, I discussed the concept of using synthetic materials to overcome some of the limitations of correcting higher-order aberrations (HOAs) with certain corneal and intraocular surgical procedures. Perhaps even more exciting is the concept of nonsurgical HOA correction with synthetic materials like good old spectacles and contact lenses. The sky's the limit for optometry if such an approach can work.

Physical Limitations

Just as with corneal- and lens-based surgery, point-to-point Zernike pupil correction is the key. But with spectacles and contact lenses, the limitations aren't surgical or biological. They are inherent in the devices themselves.

Spectacle frames are a perfect example of these physical limitations. HOA- correcting, programmed optics like lens-let arrays and diffraction gratings can be built into the center of spectacle lenses very effectively with electromagnetic films, photosynthetic processes and even nanoconstruction. These methods have been used for years with great results in high-powered telescopic systems. And when applied to ophthalmic lenses, they are not outrageously expensive.

A spectacle lens system with HOA-correcting optics in the center offers the potential for a unique combination of corrected vision: High-resolution vision when looking directly at a target through the center (the "sweet spot"), and normal lower-order correction with scanning gaze.

This type of correction could be very useful for certain vocational and avocational needs, as well as for driving, especially if the "sweet spot" reduces a lot of the annoying effects of fourth-order spherical aberrations. This would address one of the biggest problems people face with aging: Reduced mesopic and scotopic contrast sensitivity.

Look Good While Seeing Good

One important aspect of HOA-correcting spectacle lenses, indeed, their potential for success, is the ability to mount these programmed optics in stable and, of course, fashionable frames. To paraphrase Billy Crystal, "It's better to look good than to see good, my darling!"

Clinical trials comparing HOA-correcting spectacle lenses to standard lenses have shown great success. More than 90% of cohorts preferred the HOA-correcting lenses. But these trials were conducted in controlled conditions through phoropter-like instruments or trial frames. The real test and value of these HOA-correcting spectacles must come from real-world, cosmetically acceptable frames.

That real-world test is underway with the first commercially available HOA-correcting spectacle lens (iZon by Ophthonix, San Diego). After a refraction through a special wavefront aberrometer, the patient selects from a limited number of frames suitable for mounting the programmed lenses. The practitioner forwards the prescription to a designated lab for fabrication and mounting.

It will be interesting to learn how enthusiastically patients embrace this option, no doubt at premium prices, and even more interesting to learn their satisfaction with HOA correction. If acceptance is high, wavefront aberrometry will change the face of spectacle correction.

Next Up, Contact Lenses

And what about that other nonsurgical, synthetic correction: contact lenses? That has even more interesting potential than spectacles.