Evaluation of Deep Topical Fornix Nerve Block Versus Topical Anaesthesia Procedure

Overview

General anaesthesia now a days is not the first choice in phakic intra ocular lens surgery (Phakic IOL) , the short duration of the surgery, general anaesthesia complications, decrease the length of hospital stay and decreasing the costs direct the interest to the regional anaesthesia By the time the traditional retro and peribulbar injections recede to a newer techniques that is safer and cheaper, sub tenon's block using a blunt needle took over due to the more safety profile Even though, still serious problems can occur specially in patients with long axial length. Deep topical fornix nerve block anaesthesia (DTFNB) and topical anaesthesia gradually took over with promising and successful results, decreasing length of hospital stay and increasing patient satisfaction and fewer margins of complications. In this study the investigators compared topical anaesthesia alone with DTFNBA in patients undergoing posterior chamber phakic IOL surgery (Visian ICL).

102 patients scheduled for elective ICL/TICL implantation surgery were enrolled in this study after obtaining approval from the institutional ethical committee and written patients consent. the investigators are planning a study of matched sets of patients receiving the case and control treatments with 1 matched control(s) per experimental subject. Prior data indicate that the probability of a treatment failure among controls is 0.05 and the correlation coefficient for exposure between matched experimental and control subjects is 0.1. The true odds ratio for failure in experimental subjects relative to control subjects is 0.1, so the investigators needed to study 51 experimental subjects with 1 matched control(s) per experimental subject to be able to reject the null hypothesis that this odds ratio equals 1 with probability (power) 0.7. The Type I error probability associated with this test of this null hypothesis is 0.3. All patients were assessed and only those cooperative understanding patients who were deemed suitable for topical and DTFNBA were included in the study. Very anxious patients were omitted from the study. All the operations were done by one surgeon . Patients were prepared for bilateral implantable contact lens/toric implantable contact lens( ICL/TICL) procedure on the same day. Group I (1 eye) received topical anaesthetic drops and Group 2 (the second eye) received DTFNBA. Before giving the anaesthetics, a peripheral vein was cannulated and heart rate, oxygen saturation and non-invasive arterial blood pressure were monitored. Topical anaesthesia was done with 2% tetracaine local anaesthetic drops and DTFNBA was performed using two sponges (2x3mm) soaked with 0.5% bupivacaine, applied deep in the conjunctival fornices after anaesthetising the conjunctiva with tetracaine local anaesthetic drops. The sponges were removed after 15 minutes. The anaesthetic effect was tested by grasping the limbus with Castroviejo 0.12 tissue forceps. Pain was estimated by the patient using a simple pain score: no pain =0; that does not interfere with the surgical technique, discomfort=1; the surgical technique is performed with difficulty, pain=2; the surgeon is unable to continue the surgical technique . The scoring was done during different stages of surgery: lid retraction while inserting a speculum, tolerance to the microscope light, corneal incision, intraocular lens insertion, tucking of footplates, irrigation aspiration (I/A )of viscoelastic, peripheral iridectomy. The surgical technique was performed through a clear corneal 3.2 mm tunnel incision, followed by sodium hyalurounate injection, ICL implantation and unfolding, tucking of trailing footplates then side port incision and tucking of leading footplates, myostat injection, then peripheral iridectomy . The total operative time was recorded for every case. If the pain score was 0 or 1, no further management was required but if the pain score was 2 at any stage, 1% preservative free lidocaine was injected intracamerally. Parametric data were analyzed using Students t-test; non parametric data were compared using the Chi-square test. A P value of \<0.05 was considered statistically significant.