By Lisa B. Arbisser, MD
Two articles published in the Journal of Cataract & Refractive Surgery in December 2011 demonstrate different ways of potentially avoiding lens epithelial cell (LEC) transformation and proliferation in our ongoing quest to keep a clear bag. One article reports the results of an animal study of an experimental lens that holds the anterior capsule away from the optic. The second article discusses the results of a prospective study using the bag-in-the-lens technique to avoid contact. In my opinion, we are finally on the right track, working not to kill cells but to treat them with respect.
The experimental study evaluated the performance of a disk-shaped single-piece hydrophilic acrylic IOL suspended between two haptic rings connected by a pillar of the haptic material. Rabbits were implanted with the study IOL in one eye and a commercially-available single-piece hydrophobic acrylic IOL in the other. The results indicate by expanding the capsular bag and preventing IOL surface contact with the anterior capsule, the peripheral rings of the study IOL may prevent capsular bag opacification.
Researchers performed slit-lamp examination at weeks one through five. After the rabbits were euthanized, the globes were enucleated and examined by ultrasound.
While trace honeycomb PCO was noted in some study eyes, all control eyes developed moderate to marked PCO, which was more pronounced at the level of the optic–haptic junction. The mean PCO score was 0.4 ± 0.22 (SD) in the study group and 3.4 ± 0.54 in the control group (P = 0.000179). Minimal proliferative cortical material was confined to the space between the anterior and posterior rings of the study IOL haptics. Anterior capsule opacification (ACO) was absent in study eyes and mild in control eyes. There was no contact between the anterior capsule and the anterior surface of study IOLs.
The authors found the clarity of the capsular bag with the study IOL five weeks postoperatively to be remarkable. This is in marked contrast to the control IOL, which showed a large amount of proliferative cortical material anteriorly and posteriorly with significant ACO and PCO, the latter starting at the optic–haptic junctions.
The study IOL’s disk-shaped design had an anterior ring of haptic material that rested against the anterior capsule at a distance from the equator. This prevented anterior capsule contact with the optic, preventing pseudofibrous metaplasia of residual LECs attached to the inner surface of the anterior capsule. It also theoretically arrested migration of epithelial cells along the anterior capsule. The design of the study IOL has since been modified to further reduce capsular bag opacification and additional studies are being conducted in rabbits.
In the second study, 547 patients (807 eyes) underwent implantation with the bag-in-the-lens IOL technique, which included creation of a primary posterior continuous curvilinear capsulorhexis equal in size to the anterior capsulorhexis. During a mean follow-up of 26 months, no adult eye developed posterior capsule opacification (PCO). The study’s subjects ranged in age from less than 1 up to 92, with a mean of 65. Forty percent of the eyes presented with one or more ocular comorbidities. Retinal detachment occurred in 1.24 percent of eyes. The authors observed no increased risk for severe adverse events.
Among the 481 eyes without comorbidity, the mean CDVA changed from 0.52 ± 0.24 (SD) (0.276 ± 0.206 logMAR) preoperatively to 0.94 ± 0.18 ( 0.012 ± 0.053 logMAR) postoperatively. The mean postoperative achieved spherical equivalent was 0.48 ± 0.83 D, and the mean targeted refraction was 0.24 ± 0.71 D. The A-constant was modified from 118.4 to 118.04. In 19 eyes, the iris was captured by the IOL haptics postoperatively. Hypopyon occurred in three patients and toxic anterior segment syndrome in one patient.