MATERIALS AND METHODS

Our institutional ethics committee approved the study. Informed consent was obtained from 57 consecutive subjects, aged over 12 years, undergoing incision and curettage for chalazion. Subjects were excluded if they were under 12 years of age. Subjects with other ocular or systemic conditions requiring the regular use of analgesics were excluded. Subjects with previous lid surgery or chalazion surgery or lid trauma and scarring were excluded. Subjects with medical, psychological, or social conditions predisposing to a different perception of pain and in whom pain scores could not be reliably assessed were also excluded.

Patients were randomised using a centrally coordinated random table. All patients were asked to participate in the study if they fulfilled the inclusion criteria and passed the exclusion criteria. The random digit would only be revealed to the surgeon once the patient had signed the consent form. We reassured our patients that if the standard regimen did not give adequate analgesia or the patient could not tolerate the pain, supplementary analgesia would be given.

Once patients were randomised and allocated treatment, standard doses of 1.5 ml of either lignocaine 2% gel or lignocaine 2% injection were applied or injected around the chalazion, approximately 1 cm diameter. Gel was applied over the skin surface as well as onto the palpebral conjunctiva. Then we waited for 5 minutes to allow the anaesthetic to work before proceeding with incision and curettage. This involved placing a chalazion clamp over the entire region of the chalazion for haemostasis. An incision was then made in the palpebral conjunctiva underlying the chalazion. Contents were then drained and cleared with a curette.

The operated eye was pressure patched for 5 minutes or until haemostasis was achieved. The wound was then re-examined. If good haemostasis was achieved, the eye was padded for 1 day with antibiotic ointment and then removed. Immediately after the operation, while the eye was still padded, the evaluator assessed the pain experienced during incision and curettage. The pain from the local anaesthetic administration was also assessed. In the injection group, this represented the overall pain experienced from both the introduction of the needle as well as anaesthetic infiltration. In the gel group this represented any pain experienced from the application of the gel alone. A 0–100 visual analogue scale was used to assess pain. A score of zero represented no pain at all. A score of 100 represented the worst pain ever. “Fear of injection” score was evaluated preoperatively using a 0–100 visual analogue scale. A score of zero was given for no fear at all, and a score of 100 was given for worse fear ever. The patient was asked to put a cross on the 0–100 visual analogue scale. The end point for curettage in all cases was the complete removal of all removable contents.

RESULTS

Fifty seven subjects were invited to participate and 57 subjects were successfully recruited in total (n = 57) with 29 in the injection group and 28 in the gel group. The mean age of the injection group was 34.1 (SD 18.2), and the gel group 34.8 (16.9). There were 17 males and 12 females in the injection group. There were 14 males and 14 females in the gel group. The mean scores on “fear of injection” were 43.9 (28.9) in the injection group and 47.7 (36.1) in the gel group. There was no statistically significant difference in the mean age (p = 0.878), sex (p = 0.522) and scores on “fear of injection” (p= 0.668) at 5% level of significance (Table 1).

The mean total pain score in the injection group was 95.6 (49.9), and in the gel group was 57.0 (31.7). The mean pain score during anaesthetic administration was 47.0 (26.6) in the injection group and 5.5 (11.7) in the gel group. The mean pain score during incision and curettage was 48.3 (28.4) in the injection group, and 51.4 (28.8) in the gel group.

There was a statistically significant difference in mean total pain score at the 5% level of significance (p = 0.001). There was a statistically significant difference in mean pain score experienced during anaesthetic administration at the 5% level of significance (p= 0.000). There was no significant difference in mean pain score experienced during incision and curettage at the 5% level of significance (p = 0.679) (Table 2). The Mann-Whitney U test for the above mean scores were consistent with the test results in terms of statistical significance. p Values were 0.002, 0.000, and 0.712 respectively.

In the injection group there were 17 upper lid and 12 lower lid chalazia. In the gel group there were 12 upper lid and 16 lower lid chalazia. There were no statistically significant differences in mean pain scores at the 5% level of significance between upper and lower lid chalazia in general or within each group.

Overall, the injection group experienced more pain for the entire procedure. The injection group also experienced more pain on administration of anaesthesia. However, the two groups were comparable in terms of pain experienced during incision and curettage. A statistical power of 0.9394 is obtained for the main outcome measure “total pain score” (1 − β = 0.9394). The statistical power for pain during anaesthesia was 0.999. For a minimal clinically significant difference of 20 between the two groups for pain during incision and curettage, the statistical power calculated was 0.7580.

DISCUSSION

Most patients have substantial psychological fears of injections. The “fear of injection” scores among the study subjects confirmed this. The scores were similar in the two groups. This reduced the possible bias as a consequence of differences in psychological fear.

Since treatment was given in one setting and the outcomes were evaluated immediately, we did not have any problems with compliance or losses to follow which might violate randomisation and reduce comparability between treatment groups.

The two groups were comparable in age and sex distribution. This reduced any potential bias due to uneven distribution of study subjects. This confirmation of the comparability of the two treatment arm subjects after randomisation added further to our confidence that any difference in outcome could be truly attributed to the test treatment.

None of the study subjects included were unable to tolerate the incision and curettage procedure as a result of inadequate analgesia and unbearable pain. All subjects received the designated treatment. None of the gel group required reversion to conventional injection anaesthesia because of inadequate anaesthesia by lignocaine gel.

Specific measures were taken to maintain the integrity of randomisation. One person using a random table centrally coordinated the randomisation. Treatment arms were revealed to the surgeon only after enrolment in the study. This reduced any bias as a result of prior knowledge of the treatment arm and subsequent recruitment. The comparability in terms of group size, age, sex, and fear of injection further consolidated the integrity of the randomisation.

Ideally, patients, treatment team, and evaluators should be kept ignorant of group allocation and treatment group. We had considered the use of normal saline as placebo for injection and methylcellulose as placebo for gel. However, we would not be able to compare the pain scores for anaesthetic administration, which was one of our main outcome measures. Placebo was therefore not used and complete blinding was not achieved.

Another limitation of our study was the potential bias due to surgeon variation. We tried to minimise the variation by including only surgeons with similar level of experience. The use of randomisation should, however, reduce or eliminate any known or unknown confounders including surgeon variation.

We would also like to share some of the experience and practical tips gained from the verbal feedback of our patients, which may reduce patient discomfort. Regardless of whether gel or injection anaesthesia was used, the pressure effect of the clamping of the chalazion clamp and curettage is often the most unpleasant part of the procedure besides injection.

Keeping the clamping time as short as possible will cause the least discomfort to patients. We may consider adding either lignocaine 2% solution or lignocaine 2% gel using a cannula into the incision opening before curettage. Immediate postoperative discomfort can also be reduced by patching the eye with lignocaine 2% gel for 5 minutes or until haemostasis is achieved before irrigation and patching with conventional antibiotics.

CONCLUSION

We conclude that 2% lignocaine gel is effective in chalazion surgery especially in lowering the pain due to anaesthetic administration. This method of anaesthesia would be particularly useful in patients who have distressing fears of injection and in whom poor cooperation renders the patient vulnerable to needle related injuries.