In the past few years in ophthalmology, our
intraocular lens options have multiplied and our patient expectations have increased in a similar fashion. In addition to our
accommodating,
multifocal, and astigmatic correcting toric IOLs, we now have a wide array of monofocal lenses – each affecting different amounts of higher order spherical aberration. These “new technology IOLs” receive higher reimbursement in ASC settings, but do they deliver better results?
The answer is yes. Studies by McCulley et al (Awwad ST, Warmerdam D, Bowman RW, Dwarakanathan S, Cavanagh HD, McCulley JP. Contrast sensitivity and higher order aberrations in eyes implanted with AcrySof IQ SN60WF and AcrySof SN60AT intraocular lenses. J Refract Surg. 2008 Jun;24(6):619-25) demonstrated improved contrast sensitivity under high and low glare conditions with the SN60WF aspheric lens compared to the SN60AT. Rapisara et al (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 Sep;23(7):639-48) also found that contrast sensitivities with the Alcon SN60WF, AMO Tecnis Z9000, and B&L LI61AO were better than their spherical counterparts.
While these results are promising, there is still much to this science we do not understand. For example, we are unsure what the ideal total spherical aberration is ideal for best vision. For now, the general consensus is that the goal should be set to as close to zero as possible. How is this accomplished? For now, only one device is commercially available to measure cornea-only higher order aberrations – the Nidek OPD Scan II (several other topography devices can be software upgraded to perform this function as well now). Measuring corneal higher order aberrations would appear the best way to select an aspheric lens (or perhaps a positive spherical aberration lens for patients who have undergone hyperopic LASIK) to maximize results for patients.
While patient demands continue to grow in cataract surgery, with technological advances we may be able to meet our patients’ expectations confidently.
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