ASTIGMATISM

The anti-astigmatic effect of limbal relaxing incisions (LRIs) appears to remain stable over the medium term, according to a study by Rongxuan Lim, who is a resident, and Luca Ilari FRCS, at the Princess Royal University Hospital, South London Healthcare Trust, NHS, UK. In their study involving 22 eyes of 17 patients who underwent LRIs to treat a mean preoperative keratometric astigmatism of 2.26 D (min 1.2 D, max 3.6 D), the mean postoperative astigmatism was 1.31 D (min 0.3 D, max 4 D) at two weeks' follow-up, 1.24 D (min 0.2 D, max 3.9 D) at six weeks' follow-up, and 1.23 D (min 0.4, max 4.7 D) at an average of 3.41 years' follow-up. “LRIs remain an attractive option for reducing astigmatism, given their stability over time,†Dr Lim said at the 16th ESCRS Winter Meeting in Prague. The patients in the study underwent the LRIs between November 2006 and November 2008. Their age at the time of surgery ranged from 49.8 years to 86.9 years, and their mean age was 77.9 years. All had at least 2.58 years of follow-up. The average length of follow-up was 3.41 years and the longest follow-up of 4.24 years. At the patients’ most recent assessment, Dr Ilari and Dr Lim measured their corneal astigmatism and topography using the Pentacam and compared their findings with data that had been collected preoperatively, two weeks and six weeks postoperatively. They performed their statistical analysis using the Wilcoxon twotailed matched-pair test. They noted that there was no statistically significant difference between the average keratometric astigmatism at two weeks' and six weeks' follow-up (p=0.28), nor between those values at six weeks and at a mean of 3.41 years follow-up (p=0.94). On the other hand, the surgically induced astigmatism, was significantly less at six weeks' follow-up than it was at two weeks' follow-up (p=0.0004). However, the surgically induced astigmatism at six weeks was statistically similar (p=0.28) to that at a mean of 3.41 years of follow-up. In addition, when they divided the overall group into those having with-therule astigmatism and those having againstthe- rule astigmatism, both groups showed a similar pattern of astigmatic stability as the main group.

Dr Lim noted that, according to a recent survey, toric intraocular lenses and LRIs are the most popular forms of astigmatism correction. LRIs have the advantage of being cheaper and usable with any design of intraocular lens. However, they require some additional instruments and have a reputation for being less predictable than toric IOLs. Moreover, they carry a risk of infection and perforations and can exacerbate postoperative dry eye symptoms. She added that although a few small studies have shown that the astigmatic correction LRIs provide is stable for up to a year, the data is sparse for results beyond that length of time. “In our study, the astigmatic effects of limbal relaxing incisions remain stable from six weeks postoperatively to an average follow-up of 3.41 years. Thus, limbal relaxing incisions remain a competitive option for reducing astigmatism,†she said.