Capsular bag stability

Findings after two years of follow-up in a contralateral eye-controlled clinical trial comparing two single-piece, aspheric, acrylic intraocular lenses (IOLs) differing only in material, demonstrate slight differences in rotational stability and posterior capsule opacification (PCO) favouring an IOL constructed of a glistening-free (G-free) hydrophobic acrylic (PodEye, PhysIOL) over the hydrophilic acrylic IOL comparator (Pod AY, PhysIOL). Overall, however, the results show that the symmetrical, bifid open-loop haptics design shared by the two implants provides excellent capsular bag stability and is associated with a low amount of PCO, according to Oliver Findl MD. “To my knowledge this is the first clinical trial to isolate the effect of IOL material on capsular bag performance and PCO inhibition,” stated Dr Findl, Chief, Department of Ophthalmology, Hanusch Hospital, Vienna, Austria. Providing perspective on the findings, he said: “IOL centration, stability within the capsular bag, and the avoidance of PCO are all critical for achieving good visual quality after cataract surgery and especially with aspheric, toric, and multifocal optics. For every 3° of rotational misalignment, the efficacy of toric IOL correction is reduced by 10%. Today, PCO remains the most common long-term ‘adverse event’ after cataract surgery, and it tends to be higher with plate haptics than with an open-loop design.” CLINICAL COMPARISON Dr Findl conducted the prospective study that included 80 eyes of 40 patients scheduled for bilateral cataract surgery in a single-centre study. Implantation of the two IOLs was determined by randomisation. Follow-up examinations were conducted at one hour, one week, three months, one year, and two years after surgery and included measurements to determine rotation, decentration, and tilt. PCO was quantified at one and two years using dedicated software to analyse retroillumination images. Mean ± standard deviation (SD) rotation between one hour and three months after surgery was minimal with both IOLs, but significantly less with the G-free hydrophobic IOL compared with the hydrophilic lens (1.6 ±1.61° vs 2.4 ±1.85°; P=0.016). Similarly, there was very little rotation of either IOL between one and two years, and while it was less with the G-free hydrophobic IOL than with the hydrophilic IOL, the difference did not achieve statistical significance (1.8 ±1.0° versus 2.3 ±1.3°; P=0.09). “Typically, most IOL rotation happens within the first three months after surgery. The 2.4° of rotation with the hydrophilic IOL is similar to what is seen with other lenses on the market, while the amount of rotation of the G-free hydrophobic IOL, both early after surgery and during the second year of follow-up, is within the noise level of the analysis,” Dr Findl said. “One might expect a tendency for more rotation in very myopic eyes with larger capsular bags. We found no correlation between axial length and amount of rotation for either IOL, although because there were very few myopic eyes, it is not possible to reach any conclusions,” he added. Analyses of data collected at one year after surgery with a Purkinje meter showed identical, minimal decentration with both IOLs (mean ± SD, 0.30 ±0.16mm). The hydrophilic and G-free hydrophobic IOLs also displayed similarly low amounts of horizontal tilt (2.3 ±1.7° and 2.1 ±1.7°, respectively) and vertical tilt (2.9 ±1.6° and 2.5 ±1.85°, respectively). PCO scores, graded on a scale of 0 (none) to 10 (maximum), were very low for both the hydrophilic and G-free hydrophobic IOLs at one year (1.2 ±2.1 and 0.8 ±1.9, respectively) and two years (2.5 ±2.6 and 2.2 ±2.1, respectively). Although the results were numerically better for the G-free hydrophobic IOL at both visits, neither difference was statistically significant. “Obviously, this is still early follow-up for PCO, but the data slightly favour the G-free hydrophobic material,” Dr Findl said. Oliver Findl: oliver@findl.at