[Sub-tenon block for ocular globe anesthesia: a review]

Lacrimal dilator-facilitated incisionless vs. standard sub-Tenon's block: a randomized, prospective and non-inferiority comparative study

BACKGROUND/OBJECTIVES

Standard sub-Tenon's block (STB) involves incision (dissection) of conjunctiva and Tenon's capsule with the help of blunt scissors and forceps, insertion of a blunt sub-Tenon's cannula under the Tenon's capsule and injection of local anaesthetic agent. STB is frequently associated with minor complications such as chemosis and postoperative subconjunctival haemorrhage but rare sight and life-threatening complications. To reduce these minor complications, several variations of incisionless STB have been described however, there are no comparative data. One such incisionless STB involves the use of lacrimal dilator which is easily available in the operating theatre. We compared incisionless lacrimal dilator-facilitated with the standard STB for effectiveness, chemosis, and postoperative subconjunctival haemorrhage.

SUBJECTS/METHODS

After obtaining ethical approval, patients scheduled to undergo elective phacoemulsification cataract surgery were enroled to receive incisionless lacrimal dilator-facilitated STB (Group LD) or a standard STB using Wescott scissors and blunt forceps (Group WS). All patients received 3 mL 2% lidocaine without any adjuvant. No sedation was administered. Demographics of the patients, duration of the procedure, analgesia, akinesia, duration of the procedure intraoperative chemosis, and postoperative subconjunctival haemorrhage were compared.

RESULTS

Both groups were comparable for demographic data, duration of the procedure, analgesia, and akinesia (p > 0.05). The severity of chemosis and postoperative subconjunctival haemorrhage were significantly lower in Group LD (n = 32) in comparison to Group WS (n = 31) (p < 0.001).

CONCLUSIONS

Incisionless lacrimal dilator-facilitated STB decreases intraoperative chemosis and postoperative conjunctival haemorrhage in comparison to standard STB. Analgesia and akinesia are comparable in both techniques.

Correlation between sub-Tenon's anesthesia and transient amaurosis during ophthalmic surgery

PURPOSE

To verify the correlation between sub-Tenon's anesthesia and intraoperative visual loss in ophthalmic surgery.

METHODS

Sixty-four patients underwent phacoemulsification combined pars plana vitrectomy under sub-Tenon's anesthesia. Participants were investigated about their light perception at several time points: before anesthesia, immediately after anesthesia, 10 min after anesthesia without any surgical intervention or microscope illumination, and after the whole surgery. Intraoperative amaurosis was determined as that a patient could not see any light from their operative eye. The incidence rate of amaurosis at different time points and among different anesthetists was analyzed.

RESULTS

The rate of intraoperative amaurosis was 0%, 1.56%, 48.44%, and 95.31% at several time points, respectively: before anesthesia, immediately after anesthesia, 10 min after anesthesia without any surgical intervention or microscope light exposure during the interval, and immediately after the whole surgery, presenting a significantly time-dependent increase (P < 0.01). There was no correlation between the amaurosis and different diseases and anesthesiologists. The amaurosis was transient, and all operative eyes could perceive light on the first postoperative day.

CONCLUSIONS

Sub-Tenon's anesthesia contributes to the intraoperative amaurosis during operation. Temporary interruption of optic nerve conduction by the anesthetic could be a credible explanation. The amaurosis is transient and reversible, requires no additional treatment, and should not be considered as a surgical complication.