ANAESTHESIA

Results of a prospective comparative study evaluating macular thickness changes after uneventful cataract surgery indicate that further study is warranted to establish the safety of intracameral lidocaine for surgical anaesthesia. The research was conducted by ophthalmologists from Balikesir University Medical Centre, Balikesir, Turkey, and presented by Sitki Samet Ermis MD, at the XXXI ESCRS Congress in Amsterdam.

The study randomised 78 eyes of 59 consecutive patients with senile cataract to receive anaesthesia using topical lidocaine alone or supplemented at the beginning of the procedure with an intracameral injection of 0.5 cc preservative-free lidocaine one per cent. All patients underwent spectral domain optical coherence tomography (SD-OCT) imaging preoperatively and at one week, one month and three months postoperatively. Macular thickness values were determined for each of nine sectors defined by the Early Treatment Diabetic Retinopathy Study, and the data were used to calculate changes from baseline in the central fovea and the inner and outer macular zones.

Mean thickness for each of the three areas did not differ significantly between the two study groups preoperatively and increased in both groups at all follow-up visits. Comparisons between groups showed no significant difference at any time point for the changes in the central fovea and outer macular zone. However, the increase in inner macular zone thickness was significantly greater in the supplementary intracameral lidocaine group compared with eyes receiving topical lidocaine at both the one week (3.21 vs. 2.83 microns; p=0.04) and one month (7.94 vs. 6.35; p=0.03) assessments.

Study limitation

“The main limitation of this study is its relatively small sample size, which is due to the elimination of a considerable number of eyes with lens opacities preventing reliable preoperative SD-OCT measurements. However, the results are fortified by its prospective, randomised, double-masked design,” said Dr Ermis. “We believe further in vivo human studies with a larger sample size are needed in order to reach a definitive conclusion about the fate of ganglion cells after cataract surgery under intracameral lidocaine anaesthesia.”

Dr Ermis noted that cystoid macular oedema remains one of the most common causes of unfavourable visual outcomes after uneventful cataract surgery. While its pathogenesis is thought to involve breakdown of the blood-retina barrier leading to fluid accumulation in the outer retinal layers, an inflammatory process in the neurosensory retina, including the ganglion cell layer, may also play a role.

“The architecture of the perifoveal macular area includes four to six layers of ganglion cells. These perifoveal ganglion cells may be primarily affected by a surgically-induced inflammatory process, but also by the posterior accumulation of lidocaine after intracameral administration. The latter phenomenon could explain the greater increase in perifoveal macular thickness in the intracameral lidocaine group,” he said. He added that findings from previous experimental and human studies show that intracameral lidocaine is potentially toxic to the retina if it diffuses to the posterior segment. There have been reports of patients experiencing transient vision loss after receiving intracameral lidocaine.