CME AETIOLOGY

Faster, less traumatic microincision cataract surgery techniques and sophisticated IOL designs have done much to reduce the incidence of cystoid macular oedema (CME) in recent years, but the specific aetiology of the disease remains elusive and the condition may occur even after uncomplicated surgery in low-risk eyes, according to a French researcher. “Along with posterior capsule opacification, CME remains a persistent but relatively rare problem for the modern cataract surgeon,” Gilles Lesieur MD told delegates attending the annual meeting of the French Implant and Refractive Surgery Association (SAFIR).

Characterised by the collection of fluid in the macula and most often associated with inflammation following cataract surgery, CME is the main source of visual deterioration following uncomplicated cataract surgery. The incidence of macular oedema in the scientific literature is usually about one per cent to two per cent, noted Dr Lesieur, an ophthalmologist in private practice in Albi, France. While the specific aetiology is not fully understood, factors believed to contribute to its development include light toxicity, vascular pathologies, uveitis, diabetes, epiretinal membrane, IOL sterilisation, prostaglandin use, complicated surgery and long surgery times, he said. “We should bear in mind J R Wolter’s famous quote that every time a surgeon performs a phacoemulsification he opens a Pandora’s box, provoking potentially a range of complex and dangerous ocular reactions,” he said.

The goal of Dr Lesieur’s retrospective study was to analyse the incidence of CME after implantation of four different hydrophilic acrylic microincision implants in 3,871 patients between 2006 and 2012. The Akreos MICS (Bausch + Lomb) was implanted in 376 patients, with nine cases of CME; the CT Asphina (Carl Zeiss Meditec) in 780 patients, with 17 CME cases; the MicroSlim (PhysIOL) in 670 patients, with two cases of CME; finally, the Micro AY (PhysIOL) was implanted in 2,045 patients, with 13 CME cases. The total CME incidence for all four lenses combined was 1.06 per cent, said Dr Lesieur, which is in conformity with that found in the scientific literature. Looking at the overall results, Dr Lesieur said that there was no statistically significant difference between the CME rates found with the MicroSlim and Micro AY lens or between the Akreos and Asphina IOLs. However, a statistically significant difference was found between the two PhysIOL lenses and both the CT Asphina and the Akreos MICS lenses. Interestingly, Dr Lesieur noted that while the contralateral eye of affected patients was not systematically implanted with the same IOL as that of the study eye, many still presented with CME in that eye as well. In terms of aetiology, Dr Lesieur said that epiretinal membrane, diabetes and vascular pathology were all implicated to some degree in patients implanted with Akreos MICS, CT Asphina and Micro AY lenses. All of the CME cases resolved after medical treatment, with the exception of two patients that required surgical intervention for ablation of epiretinal membrane and injection of intravitreal dexamethasone 0.7mg. No anomaly was found in the sulcus or the angle of the various IOLs, which he said seemed to rule out, for the moment, the theory of possible contact between the haptic and the ciliary body as being responsible for the CME.

He concluded that the differences found between the CME rates of the IOLs in his study may partly be explained by the presence of comorbidities in these patients. “We need further research to elucidate the possibility of a correlation between the haptic design and irritation of the ciliary muscle and we are currently conducting a ultrasound biomicroscopy study to examine this very question,” he said. * Dr Lesieur would like to especially thank Laure Gobin PhD, statistical analysis; Sophia Fredéric and Sabrina Vieusses, orthoptists