Do we need prolonged local anaesthesia for cataract surgery by phacoemulsification?

Sir,

We read with interest an article by Bajwa et al. on “Comparative evaluation of ropivacaine and lignocaine with ropivacaine, lignocaine and clonidine combination during peribulbar anaesthesia for phacoemulsification cataract surgery”.[1]

The phacoemulsification procedure for cataract removal has revolutionized cataract surgery largely. Phacoemulsification with a small incision is the method of choice for most cataract surgeons. The procedure provides a controlled, faster and safer method of removing the nucleus. The small wound provides rapid visual recovery for the patient. Injection-related complications of peribulbar anaesthesia for cataract surgery have been reported, as it is a blind procedure.[2] To avoid the complications, the trend is towards the topical anaesthesia with anaesthetic drops alone or combined with intracameral preservative-free lidocaine.[34] Lidocaine 2% jelly has been tried in phacoemulsification.[5] Single instillation of lidocaine 2% jelly was associated with pain scores comparable to those with topical eye drop anaesthesia. When the jelly was readministered shortly before surgery, the pain scores were comparable to those with intracameral anaesthesia. In this era of demand for immediate visual recovery, do we need an anaesthetic agent having prolonged duration of action? The authors should have conducted the study of the said anaesthetic agents in ophthalmic surgeries that require a long duration.

The authors state in the abstract section that 200 patients of both sexes aged 50–80 years of American Society of Anesthesiologists grade I and II, scheduled for phacoemulsification cataract surgery under monitored anaesthesia care, were enrolled for the study. While elaborating the methodology, the age was stated to be 50–70 years. Why is there this discrepancy?

The authors state that ropivacaine was selected for administering peribulbar block because of its favourable cardiac and neurologic profile as compared with bupivacaine. At the same time, patients having cardiac diseases and those on antiepileptic and antipsychotic drugs were excluded from the study. It has been stated in a study that although ropivacaine is less cardiotoxic than bupivacaine, it has a higher threshold for central nervous system toxicity than bupivacaine.[6]

In the methodology section, it was written that the surgeon and the patient assessed quality of block. How did the patient assess this?

In our opinion, the authors should have used an applanation (hand held or some other form) tonometer instead of the Schiotz tonometer as it does not give accurate readings.

Ropivacaine is said to have a vasoconstrictive effect, which helps to reduce the intraocular pressure (IOP). At the same time, superpinky ball and ocular massage was given to reduce the ocular pressure. We think that ocular massage should not have been given if the drug reduces the IOP. Does the drug have an effect on the optic nerve vessels causing damage to its fibres and affecting visual outcome after the phacoemulsification?

Reference no. 19 cited by the authors in support of reduction of IOP by clonidine, on Pubmed search by us, states that there is no significant difference in baseline IOP and post-peribulbar IOP.

The authors say that the mild sedative effect of clonidine was an added advantage as the patients remained calm and composed during the entire surgical period and had better sedation scores than patients who were administered ropivacaine. How did addition of clonidine in peribulbar (in the ropivacaine–clonidine group) cause sedation? Was it because of good quality block in the ropivacaine–clonidine group or possibility of systemic absorption of clonidine? In case of systemic absorption, issues related to the systemic absorption of other anaesthetic agents used will arise.

In conclusion, the authors say that ropivacaine is considered a good local anaesthetic agent available that has a favourable side-effect profile. Nevertheless, we have seen that 3 mL 2% xylocaine and 2 mL 0.5% bupivacaine does work for peribulbar anaesthesia in cataract surgery without any side-effects.