Two studies recently published in the Journal of Cataract & Refractive Surgery address the effectiveness and safety of light-adjustable IOLs. One paper concludes that the lenses successfully correct postoperative refractive errors and the other that the adjustment and lock-in procedures do not add to the endothelial damage caused by cataract surgery.
I believe that this is a promising technology. The first study describes good results for postoperative corrections of spherical and cylindrical errors of up to 2 D. It is believed to be the first report of combined correction of spherical and cylindrical refractive errors after cataract surgery using light-adjustable IOLs in eyes with axial myopia. The second paper, a specular microscopic study that evaluated corneal endothelial safety after irradiation of the light adjustable lens, confirms the results of a study we performed here at the Moran Eye Center using cat eyes that was published in the Journal of Cataract & Refractive Surgery in 2007.
Part of an ongoing prospective clinical trial in Germany, the first study reports pilot results for 21 patients (21 eyes) with axial myopia and astigmatism who underwent cataract surgery with light-adjustable IOLs. After implantation of the lenses, the eyes were treated for refractive adjustments ranging from - 0.75 to +1.75D spherical power and 0.00 to -1.50 D cylindrical power. Once the desired correction was achieved, the power of the IOL was locked in.
Twelve months postoperatively, 20 of the 21 eyes (96 percent) were within ± 0.50 D of the intended refractive outcome and 17 eyes (81 percent) were within ± 0.25 D. The remaining eye suffered from tear film instability and had a 0.325 D change in mean refractive spherical equivalent (MRSE). Meanwhile, MRSE changed less than 0.250 D in the other 20 eyes from one month after lock-in through the 12-month postoperative visit. Uncorrected distance visual acuity (UDVA) significantly improved and corrected distance visual acuity was maintained compared with preoperative measurements.
Although the results show precise adjustment of sphere and cylinder up to 2.00 D, the authors say most patients required a second adjustment to fine tune residual refractive errors before lock-in. They conclude that this technology may provide greater confidence in final refractive outcomes, a boon since expectations for better UDVA among cataract patients are increasing.
The second study assessed the change in endothelial cell density (ECD) in 10 patients (10 eyes) who underwent phacoemulsification with light-adjustable IOL implantation. Each patient underwent two adjustments and two lock-in procedures with a light-delivery system between two and four weeks postoperatively.
Specular microscopy showed a mean ECD of 2344 cells/mm2 preoperatively. One week postoperatively, prior to lock-in, the mean overall central ECD was 2047 cells/mm2, representing an endothelial cell loss of 12.6 percent compared with preoperative measurements. Six months postoperatively, mean overall central ECD was 2130 cells/mm2, a 9.1 percent loss from preoperative values, representing mild recovery. There was no statistically significant difference in the coefficient of variation or percentage of hexagonal cells at either postoperative evaluation.
The authors say that the endothelial cell loss in this study after six months is similar to values previously reported for phacoemulsification with IOL implantation. Although the results include only 10 patients, they corroborate the authors' clinical observations, as well as results of previous in vivo animal studies, which found no endothelial damage from the UV irradiation of light-adjustable IOLs. The authors conclude that the light-adjustable IOL irradiation protocol for adjustment and lock-in procedures did not appear to add to the endothelial damage caused by cataract surgery, indicating its safety for the corneal endothelium.
They add that by the time they submitted the manuscript for this study, they had implanted more than 250 light-adjustable IOLs at their center, some with follow-up of more than six years. They report that there have been no cases of corneal decompensation or pseudophakic bullous keratopathy.