Prospective evaluation of deep topical fornix nerve block versus peribulbar nerve block in patients undergoing cataract surgery using phacoemulsification

E. S. Aziz1,* and A. Samra2

1Department of Anaesthesia, Faculty of Medicine, Cairo University, 35A Abou Elfeda Street, Zamalek, Cairo, Egypt and 2Department of Ophthalmology, Research Institute of Ophthalmology, Cairo, Egypt*Corresponding author

Accepted for publication: March 22, 2000

Abstract

We compared the efficacy of deep topical fornix nerve block anaesthesia (DTFNBA) versus peribulbar nerve block in patients undergoing cataract surgery using phacoemulsification. We studied 120 patients, allocated randomly to two groups. Group 1 (n=60) received peribulbar block with 5 ml of a 1:1 mixture of 0.5% plain bupivacaine and 2% lidocaine supplemented with hyaluronidase 300 i.u. ml–1. Group 2 received DTFNBA with placement of a sponge soaked with 0.5% bupivacaine deep into the conjunctival fornices for 15 min. No sedation was given to either group. Analgesia was assessed by the reaction to insertion of the superior rectus suture and by questioning during the procedure. A three-point scoring system was used (no pain=0, discomfort=1, pain=2). Scoring was repeated at keratotomy, hydrodissection and hydrodelineation, phacoemulsification, irrigation and aspiration, and at intraocular lens insertion. If the patient’s pain score was 0 or 1, no further action was taken. If the pain score at any stage of the operation was 2, intracameral injection of 1% preservative-free lidocaine was given. One patient in Group 2 needed intracameral lidocaine at the stage of phacoemulsification (P>0.05) and four experienced discomfort at irrigation and aspiration (P=0.043). We conclude that DTFNBA may be a useful needle-free anaesthetic technique in patients undergoing cataract surgery using phacoemulsification.

Br J Anaesth 2000; 85: 314–6

Keywords: anaesthetic techniques, regional anaesthetic techniques, topical; surgery, ophthalmic; enzymes, hyaluronidase

General anaesthesia is hazardous in a large number of patients undergoing ophthalmic surgery, as many of them are elderly with multisystem disease. For diabetic patients, local anaesthesia is preferable as it reduces, to a great extent, the endocrine response to surgery.1 Peribulbar block is becoming increasingly popular, as it is safer than retrobulbar block.2 However, insertion of a needle near the eye is associated with the necessity to stop anticoagulant therapy, introduces the risk of retrobulbar bleeding and potential perforation of the globe. Such risks may necessitate the use of topical anaesthesia, although this is unusual. The use of deep topical fornix-applied nerve block anaesthesia has been reported in cataract surgery by Rosenthal.3 It involves placement of local anaesthetic into the conjunctival fornices, from which the local anaesthetic diffuses across the conjunctiva into the peribulbar space and into the scleral nerves behind the eyes. In this study, we compared deep topical fornix nerve block anaesthesia (DTFNBA) with peribulbar nerve block in patients undergoing cataract surgery using phacoemulsification.

Methods and results

One hundred and twenty patients scheduled for elective intraocular surgery were enrolled in the study after we had obtained approval from the institutional ethics committee and patient consent. All patients had been assessed as suitable for a regional block technique and were unpremedicated. Patients were allocated randomly to one of two groups (closed envelope method). Group 1 (n=60) received peribulbar block. Group 2 (n=60) received DTFNBA.3 The axial length (the distance from the cornea to the retina) is usually measured as part of the ophthalmic assessment using the axial length scanner. If the axial length is 26 mm or longer, the globe is elongated.4 These patients were omitted from the study, as the risk of globe perforation if peribulbar block is used is greater.

Before the block, a peripheral vein was cannulated and heart rate, oxygen saturation and non-invasive arterial blood pressure were monitored. In both groups, the conjunctival fornices were anaesthetized with local anaesthetic drops (oxybuprocaine 0.4%) before the block was started.

Peribulbar block was performed with a 5 ml syringe and a 25 gauge, 25 mm long disposable needle using a single inferotemporal injection5 6 with 5 ml of a 1:1 mixture of 0.5% plain bupivacaine and 2% plain lidocaine supplemented with hyaluronidase 300 i.u. ml–1. With the gaze fixed straight ahead in the primary position, the injection site was identified at the junction of the lateral one-third and medial two-thirds of the inferior orbital rim. The direction of the needle was slightly medial and cephalad. The local anaesthetic was injected slowly over a period of 1 min. DTFNBA was performed using two sponges (2x3 cm) soaked with 0.5% bupivacaine, applied deep into the conjunctival fornices.3 The sponges were removed after 15 min. The surface anaesthetic effect was tested by grasping the limbus with Castroviejo 0.12 tissue forceps. A simple pain scoring system was used: no pain=0, discomfort=1, pain=2. The scoring was done at different stages of surgery: insertion of the superior rectus suture; keratotomy; hydrodissection and hydrodelineation; phacoemulsification; irrigation and aspiration; and intraocular lens insertion. If the pain score was 0 or 1, no further management was required. If the pain score was 2 at any stage of the operation, intracameral injection of 1% preservative-free lidocaine was given.

Parametric data were analysed using Student’s t-test; non-parametric data were compared using the Mann–Whitney test. A P value of <0.05 was considered statistically significant.

There was no significant difference between the patient characteristics of the two groups (Table 1).


View this table:
[in this window]
[in a new window]
 
Table 1 Patient characteristics. Values are mean (SD) and age, range
 
In Group 1, no patient experienced discomfort or pain at any stage of the operation. In Group 2, one patient experienced discomfort at the superior rectus suture, keratotomy, hydrodissection and hydrodelineation and phacoemulsification (P>0.05), and four patients experienced discomfort at irrigation and aspiration (P=0.043). At the stage of intraocular lens insertion, three patients in Group 2 experienced discomfort (P>0.05). In the only patient who experienced pain at the time of phacoemulsification, intracameral injection of 1% preservative-free lidocaine was applied.

The numbers of patients in each group with different pain scores at each stage of surgery are shown in Table 2.


View this table:
[in this window]
[in a new window]
 
Table 2 Numbers of patients in relation to pain score at different stages of the operation. Data were analysed using the Mann–Whitney test. *P = 0.043 between groups
 
Comment

Peribulbar block has gained popularity over the last few years, as it is safer than the traditional retrobulbar block.2 4 In peribulbar block the needle tip remains outside the muscle cone, and thus the complications of retrobulbar block are avoided. However, peribulbar block has its own complications. Brain stem anaesthesia resulting from subarachnoid injection can occur if the peribulbar needle is inadvertently placed in the retrobulbar space. This is unlikely with a 25 gauge, 25 mm long needle. Extraocular muscle paresis can occur if local anaesthetic is injected directly into the muscle, or the needle may puncture a superficial vessel, causing conjunctival haemorrhage. The incidence of scleral perforation is higher with retrobulbar blocks. However, it has been reported with peribulbar block, especially if the axial length is more than 26 mm.4 These complications are avoided with the use of DTFNBA, yet a good quality of analgesia is maintained. Rosenthal3 has postulated that placement of local anaesthetic into the fornices allows absorption by the nerve trunks subserving the conjunctiva as they radiate across it. At the same time, by being absorbed posteriorly into the peribulbar space (and possibly transconally into the retrobulbar space), the posterior ciliary nerves, which supply the anterior sclera, anterior conjunctiva and limbus as well as the iris and ciliary body, are anaesthetized at their nerve roots.3

Each time a needle is introduced into the orbit there is a small but definite risk of complications. In this study, it has been shown that the use of DTFNBA offers analgesia comparable to that given by peribulbar block. Additional local analgesia may be required during lens irrigation and aspiration as there is significant patient discomfort at this stage of surgery. However, there is no akinesia with DTFNBA. This method is therefore not suitable for cataract surgery using extracapsular lens extraction; it is suitable only for surgery using phacoemulsification. The surgeon must be experienced with this type of surgery, as surgery is more difficult without akinesia. We conclude that DTFNBA is suitable for patients on anticoagulants and those who will not accept the use of injections around the eye. We recommend DTFNBA for patients undergoing cataract surgery using phacoemulsification.

Footnotes

* Corerspondign author Back

References

1 Barker JP, Robinson PN, Vafidis GC, Hart GR, Sapsed-Byme S, Hall GM. Local analgesia prevents the cortisol and glycaemic responses to cataract surgery. Br J Anaesth 1990; 64: 442–5[Abstract]

2 Davis DB, Mandel MR. Posterior peribulbar block: an alternative to retrobulbar anaesthesia. J Cataract Refract Surg 1986; 12: 182–5[ISI][Medline]

3 Rosenthal KJ. Deep topical fornix nerve block anaesthesia. J Cataract Refract Surg 1995; 21: 499–503[ISI][Medline]

4 Duker JS, Belmon JB, Benson WE, et al. Inadvertent globe perforation during retrobulbar and peribulbar anaesthesia: patient characteristics, surgical management and visual outcome. Ophthalmology 1991; 98: 519–26[ISI][Medline]

5 Apel A, Woodward R. Single injection peribulbar local anaesthesia. Aust NZ J Ophthal 1991; 19: 149–53[ISI][Medline]

6 Aziz ES. Peribulbar block using a single inferotemporal injection technique with high dose hyaluronidase. Egypt J Anaesth 1997; 31: 85–90