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Light-adjusted IOL offers targeted refraction despite higher-order aberrations
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CHICAGO — The Light Adjustable Lens, which allows for power adjustment after implantation, increased higher-order aberrations but met refractive targets, according to study results presented here.
 Roberto Bellucci |
"Total internal aberrations were a little higher than expected, especially at 6 mm [aperture diameter]," Roberto Bellucci, MD, said during Refractive Subspecialty Day preceding the joint meeting of the American Academy of Ophthalmology and Middle East Africa Council of Ophthalmology.
In the study of 20 eyes implanted with the Light Adjusted Lens (LAL; Calhoun Vision) after phacoemulsification, postoperative mean sphere was –0.49 D and mean cylinder was –0.87 D, but emmetropia was not always the surgical goal, Dr. Bellucci said. Postoperatively, between day 20 and 28, ultraviolet light was introduced that reacted with the IOLs silicone material to change the shape of the lens and, thus, its power.
Total higher-order aberration at the 4-mm optical zone, as measured by a Topcon KR9000PW disc topographer using a Hartmann-Shack wavefront sensor, was 0.168 µm at the corneal plane, 0.166 µm internally and 0.236 µm for the entire eye. Spherical aberration Z4 measurements were 0.049 µm at the cornea, 0.070 µm internally and 0.044 µm for the entire eye, which although higher than expected, may be a byproduct of adjustment, according to Dr. Bellucci.
The authors performed wavefront aberrometry in patients who underwent implantation with a light-adjustable silicone IOL, manufactured by Calhoun Vision, whose power can be adjusted postoperatively by controlled application of ultraviolet light. They concluded that the spherical aberration of these lenses was greater than in historical controls measured at the same optical zone and hypothesized that this increase was likely due to the light adjustment. The study would be strengthened if the authors could show a statistically significant increase in spherical aberration comparing the pre-adjustment measurement with post-adjustment measurement. In general, spherical aberration is greater with higher dioptric IOL powers, and one might anticipate that hyperopic adjustments may induce a different change in spherical aberration than myopic, and so these variables must be part of any analysis. Of interest, there was not an increase in the amount of asymmetrical aberrations, such as coma, in the light-adjusted IOLs compared with historical controls, which is reassuring, because this can lead to image degradation that is not correctable with glasses.
– Jay S. Pepose, MD
Director, Pepose
Vision Institute, Professor of Clinical Ophthalmology, Washington University
School of Medicine, St. Louis