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Sub-Tenon’s block versus topical anaesthesia for cataract surgery
  1. A C O Cheng,
  2. H K L Yuen,
  3. R F Lam,
  4. D S C Lam
  1. Department of Ophthalmology and Visual Sciences, The Chinese University of Hong Kong, 3/F, Hong Kong Eye Hospital, 147K Argyle Street, Kowloon, Hong Kong
  1. Correspondence to: Dennis S C Lam Department of Ophthalmology and Visual Sciences, The Chinese University of Hong Kong, 3/F, Hong Kong Eye Hospital, 147K Argyle Street, Kowloon, Hong Kong;

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We read with great interest the article by Ruschen et al comparing patient satisfaction during cataract surgery with sub-Tenon’s block (STB) versus topical anaesthesia (TOP).1 The authors concluded that in the setting of day case cataract surgery, patients reported significantly higher satisfaction scores with STB than TOP.

We would like to raise two issues for discussion. Firstly, the lower satisfaction score in the TOP group may only reflect a suboptimal TOP that was given in the current study and may not be generalisable to other forms of TOP. In our experience, lignocaine gel (lidocaine hydrochloride 2%, AstraZeneca, Sweden) produces significantly better anaesthetic effects than local anaesthetic eye drops. Lignocaine gel has been previously shown to be an effective2,3 and possibly a more superior4,5 anaesthetic agent in cataract surgery, as well as giving better patient cooperation with less intraoperative supplement.5 To further evaluate the apparent lower satisfaction scores with TOP than STB, we would be grateful if the authors could provide the details of their TOP anaesthetic procedure—for example, how long before the actual surgery were proxymetacaine and amethocaine given and whether supplementary anaesthetic eye drops were allowed during the surgery?

Secondly, even though the median satisfaction score in the TOP group was significantly lower than that of the STB group, there was a much larger variation in the TOP group (fig 1). This would imply some patients were satisfied while some were dissatisfied. We certainly believe not all patients can tolerate TOP and it would be highly desirable for cataract surgeons to identify the latter group preoperatively. Were there any specific characteristics in this group showing such dissatisfaction? Moreover, we noted that there were more females (12 out of 14 patients) in the TOP group, compared to the STB group (five out of 14 patients). This difference was statistically significant (p = 0.018, Fisher’s exact test). We recognise that randomisation had been implemented in the present study and any significant differences in patients’ demographics were beyond the control of the authors. However, such difference might have impacted the satisfaction scores, as it is known that women have high rates of physical symptom reporting.6

Figure 1

 Box and whisker plot of satisfaction score with sub-Tenon’s block or topical anaesthesia. (From Rüschen et al1)

None the less, we do commend the authors’ work on this important topic. We agree with the authors that sub-Tenon’s anaesthesia may be a better choice in some patients undergoing cataract surgery. However, other forms of topical anaesthesia may produce equally good, if not better, patient satisfaction especially in selected patients.


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