By:Howard Larkin in Orlando
Pre-fragmenting cataractous lenses with a femtosecond laser before phacoemulsification appears to produce less endothelial cell loss at six months compared with eyes treated with conventional phaco only, Mark Packer MD, FACs, CPi, Eugene, Oregon, Us, told the American Academy of Ophthalmology. he discussed an ongoing prospective contralateral eye study that involved 309 femto-laser treated eyes and 123 conventionally treated control eyes. Dr Packer noted that endothelial cell loss is widely recognised as a barometer of ocular health after anterior segment surgery. "We were looking at safety, not efficacy, and in terms of safety i think we are doing quite well with this new technology."
Reduced phaco energy
In theory, reducing the amount of phaco energy and fluid volume required for lens removal using femto pre-fragmenting could result in less disruption during surgery, leading to less corneal oedema, anterior chamber cells and flare one day after surgery, as well as reduced long-term loss of endothelial cell density attributable to surgery. In other studies, reductions in phaco energy ranging from 40 per cent to 100 per cent, depending on cataract grade, have been documented.
In this study, harvey Uy MD, Manila, Philippines, examined the hypothesis by using a LensAR femtosecond laser to pre-fragment lenses in test eyes while using conventional phaco only in the contralateral eye when indicated. Dr Uy performed all the procedures using standardised technique and phaco settings on an Alcon infinity system with OZil, and implanted Acrysof sA60 AT intraocular lenses in all eyes. Endothelial cell count was measured at baseline and three and six months after surgery using an automated Konan CellCheck XL. While this device does lead to some variation in cell counts, Dr Packer said that it is adequate for technology assessment when used on a sample size large enough for statistical analysis of standard deviations.
At three months, overall outcomes were not statistically significant between the two groups, Dr Packer reported. In 225 eyes treated with femto pre-fragmentation, endothelial cell loss averaged 0.7 per cent, compared with a gain of 0.1 per cent for 63 eyes treated with conventional phaco (p=0.16) (see figure). Broken down by cataract grade, the femtotreated group had less endothelial cell loss that was statistically significant at 90 per cent for grades 1 and 3, but no significant differences were seen for grades 2 and 4. "What is most striking is the very small degree of endothelial cell loss in either group. it was essentially zero in the phaco group. By comparison published studies show about six to seven per cent and 10 to 11 per cent in complicated eyes. So to see one per cent is quite an achievement. My hat is off to Dr Uy," Dr Packer noted.
At six months, 309 femto-treated eyes averaged a loss of 0.4 per cent compared with 123 phaco-only eyes averaging a 2.6 per cent loss, a result that was significant at the 90 per cent level. Only grade 1 eyes showed a significant difference at six months. Dr Packer speculated that the difference in outcomes between the two groups might be greater for surgeons with more typical endothelial cell loss ratios than Dr Uy's. Data collection and analysis are ongoing to further strengthen the statistical model.