LESS PAINFUL MICS

Micro-incision cataract surgery (MICS) performed with a combined viscoelastic anaesthesia formulation can be significantly less painful than surgery performed with topical anaesthesia alone, particularly during the IOL insertion phase of the procedure, according to the results of a study presented at a conference of the Irish College of Ophthalmologists by David Shahnazaryan MRCSI, Royal Victoria Eye and Ear Hospital, Dublin, Ireland. The study involved 68 eyes of 68 consecutive patients scheduled for MICS. They included 39 women and 29 men with a median age of 73.5 years. The Dublin investigators randomly allocated the patients to undergo MICS with either topical anaesthesia or topical anaesthesia in addition to intracameral anaesthesia with a commercial formulation combining 1.0 per cent lignocaine with a viscoelastic (Visthesia ®, Zeiss). In all procedures Dr Shahnazaryan and his associates inserted the IOLs using 2.2mm incisions and a wound-assisted technique.

During admission, patients signed consent forms and were familiarised with the visual analogue pain scale. All received an instillation of topical anaesthesia with 0.5 per cent proxymethacaine five minutes before surgery. All provided a pain score at three time points, namely, directly before surgery, directly following IOL insertion and at the conclusion of surgery at which point they gave an overall pain score for procedure. “The rationale behind this study is that because of the small size of the wound in micro-incision cataract surgery most of the tips of the IOL injectors cannot be inserted through the wound. That means we have to use the wound-assisted IOL insertion which could be associated with more pain perhaps due to wound stretching,†Dr Shahnazaryan said. Although the mean overall pain score in both groups was less than three, which corresponds to mild pain or discomfort, it was significantly less in the Visthesia group, at 1.6, compared to 2.8 in the topical anaesthesia alone group (p=0.009).

Furthermore, none of the patients in the Visthesia group reported a pain score greater than four during IOL insertion, whereas eight patients (24 per cent) in the topical anaesthesia alone group reported a score greater than four at the same time point in their procedures. The duration of surgery was comparable in both groups, with mean values of 16.44 minutes in the Visthesia group and 16.35 minutes in the topical anaesthesia alone group. Moreover, a statistical analysis revealed no correlation between the duration of surgery and the pain score in either group. The effective phaco time was also comparable in both groups, with mean values of 5.7 seconds in the Visthesia group and 5.8 seconds in the topical anaesthesia alone group. There was also no correlation between the effective phaco time and the pain score in either group. “Visthesia was associated with significantly less pain and discomfort during IOL insertion. However, it is about several times more expensive and perhaps the addition of one per cent lignocaine intracameral could achieve similar effect at less cost,†Dr Shahnazaryan concluded.