Aspheric IOLs: Completing the Picture
Aspheric IOLs: Completing the Picture
After cataract removal, these IOLs replace the lens and correct for spherical aberration in the cornea.
Can patients have sharp visual acuity after cataract surgery? Well, replacing the clouded crystalline lens with a clear IOL improves vision tremendously. However, the natural spherical aberration of the cornea still exists, and conventional IOLs contribute to the problem with positive spherical aberration.
With conventional IOLs, light rays are over-refracted at the periphery of a lens system, and patients see a region of defocused light, which can decrease image quality.1 Instead of sharp, clear images, patients see a glare or blur.
The solution is the aspheric IOL, also known as wavefront-corrected IOLs because wavefront technology is the source of the design data. Some aspheric IOLs compensate for induced positive spherical aberration with negative aberration, aligning light rays for a sharper, clearer image. Others have a neutral effect by not adding spherical aberration. Patients see the results. Those with aspheric IOLs experience significantly better photopic and mesopic contrast sensitivity than patients with spherical IOLs.2 We already achieve this effect with eyeglasses and contact lenses, and now we can do it with IOLs after cataract surgery.
Three aspheric IOLs
Three lenses on the market today improve spherical aberration: the Tecnis (Advanced Medical Optics), AcrySof IQ (Alcon), and SofPort Advanced Optics (Bausch & Lomb).
SofPort Advanced Optics (AO) is the aberration-free aspheric IOL. Surgeons implant this foldable lens through an incision less than 3.0 mm. Because it uses neutral spherical aberration, the SofPort AO is particularly useful for patients who don't require significant reversal of induced spherical aberration.
The Tecnis and AcrySof IQ lenses work similarly by compensating for the induced positive spherical aberration with negative spherical aberration. For patients who complain about glare and halos and problems with night driving, and those whose vision has declined with age, these lenses are excellent options.
In fact, according to the National Highway Traffic Safety Administration, patients with aspheric lenses (in this case, the Tecnis lens) gained 67 feet of stopping time over patients with standard IOLs when driving at night.3
And in clinical testing, the Tecnis IOL gave patients up to 53% better contrast sensitivity in low-light conditions than the spherical IOL.4
Today, the Veterans Affairs system uses the AcrySof IQ as its standard post-cataract IOL, because the AcrySof material has been proven to be safe and effective.
|Aspheric IOLs fit the patients whose primary complaints are night driving, glare and halos.|
Aspherics in your practice
We're fortunate to have so many choices for our patients undergoing cataract surgery. Aspheric IOLs fit the patients whose primary complaints are night driving, glare and halos. They're also an alternative for those who aren't interested in presbyopic IOLs.
Aspheric IOLs cost more than standard IOLs, but these lenses give patients an excellent opportunity to gain clearer, aberration-free vision after surgery. Just be sure that you and your partner surgeon agree that these lenses are worth the price. OM
- Smith G, Atchison DA. The Eye and Visual Optical Instruments. Cambridge, United Kingdom: Cambridge University Press,1997:667.
- Caporossi A, Martone G, Casprini F, Rapisarda L. Prospective randomized study of clinical performance of 3 aspheric and 2 spherical intraocular lenses in 250 eyes. J Refract Surg. 2007;23:639-648.
- National Highway Traffic Safety Administration. 2003. Traffic Safety Facts 2001: Pedestrians. Washington, DC: U.S. Department of Transportation.
- Packer M, Fine IH, Hoffman RS, Piers PA. Improved functional vision with a modified prolate intraocular lens. J Cataract Refract Surg. 2004;30:986-992.
Optometric Management, Issue: June 2008