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 Table of Contents  
ORIGINAL RESEARCH REPORT
Year : 2018  |  Volume : 15  |  Issue : 1  |  Page : 1-7

Regional anesthesia for small incision cataract surgery: Comparison of subtenon and peribulbar block


1 Department of Anaesthesia and Ophthalmology, College of Medicine, University of Lagos and Lagos University Teaching Hospital, Surulere, Lagos, Nigeria
2 Department of Anaesthesia, Lagos University Teaching Hospital, Surulere, Lagos, Nigeria

Date of Web Publication23-Feb-2018

Correspondence Address:
Dr. Oyebola Olubodun Adekola
Department of Anaesthesia, College of Medicine, University of Lagos and Lagos University Teaching Hospital, P.M.B 12003, Surulere, Lagos
Nigeria
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/jcls.jcls_5_17

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  Abstract 


Background and Objective: The recent trend in cataract surgery is the use of regional ophthalmic nerve blocks or topical anesthesia. We determined and compared the effect of peribulbar and subtenon block on pain and patients' satisfaction, following small incision cataract surgery (SICS). Methods: This was age-sex-matched comparative study involving 462 ASA I-III patients, aged 18 years and above scheduled for SICS. They were assigned to receive either peribulbar block (Group P) or subtenon (Group ST). The pain score and patients' satisfaction with the anesthetic experiences were recorded by a study-masked anesthesiologist during surgery and postoperatively at 30 min and 1, 2, 4, and 24 h. Results: The median numeric rating score was significantly lower in the subtenon group than the peribulbar group: During surgery, Group ST 1 (1) versus group P 1.5 (2.25), P < 0.001. At 30 min after surgery, Group ST 0 (1) versus Group P 1 (2.5) versus P < 0.001, and at 1 h after surgery, Group ST 0 (1) versus group P 1 (2), P = 0.002. Ten patients had akinesia in the peribulbar group compared with one in the subtenon group. Chemosis was significantly higher in the subtenon group 10 (3.2%) than in the peribulbar group 0 (0%), P = 0.035. Similarly, a significant difference was not with subconjuctival hemorrhage; subtenon 14 (4.5%) versus peribulbar 2 (1.3%), P = 0.105. Conclusion: The use of subtenon block resulted in lower pain scores and higher patient's satisfaction than peribulbar block. However, subconjuctival hemorrhage and chemosis were more common with subtenon block.

Keywords: Complications, pain, peribulbar block, small incision cataract surgery, subtenon block


How to cite this article:
Adekola OO, Aribaba OT, Musa K, Olatosi JO, Asiyanbi GK, Rotimi-Samuel A, Onakoya A, Akinsola FB. Regional anesthesia for small incision cataract surgery: Comparison of subtenon and peribulbar block. J Clin Sci 2018;15:1-7

How to cite this URL:
Adekola OO, Aribaba OT, Musa K, Olatosi JO, Asiyanbi GK, Rotimi-Samuel A, Onakoya A, Akinsola FB. Regional anesthesia for small incision cataract surgery: Comparison of subtenon and peribulbar block. J Clin Sci [serial online] 2018 [cited 2018 Aug 14];15:1-7. Available from: http://www.jcsjournal.org/text.asp?2018/15/1/1/226037




  Introduction Top


Cataract surgery is the most common surgical procedure in ophthalmology and is known to be the most cost-effective of all surgical procedures.[1] Cataract surgery has been reported to have a good safety profile.[1],[2] Eye surgeries had been performed with little or no anesthesia for almost a 1000 years until 1884 when cocaine hydrochloride was discovered by Carl Koller.[3]

However, the global trend for anesthesia during cataract surgery has shifted from general anesthesia, sedation, and hospitalization to regional ophthalmic block (ciliary ganglion, ophthalmic, oculomotor, abducent, and trochlear nerves) as well as topical anesthesia with day case management due to the improvement in cataract surgical techniques. This improvement in cataract surgical services is predicated on reduced surgical wound size and self-sealing architecture as well as better intraocular lenses design, less tissue manipulation, and modern instrumentation.[1],[4],[5],[6]

The operative technique includes extracapsular cataract extraction, small incision cataract surgery (SICS), phacoemulsification, and phacolaser methods.[1],[4],[5],[6]

The choice of regional block varies from retrobulbar or peribulbar block to subtenon, subconjunctiva, intracameral, topical anesthesia, or a combination of any of the blocks.[2],[3],[4],[5] The needle tip remains outside the muscle cone with peribulbar (extraconal) block technique.[7] The local anesthetic agent is injected under the Tenon's capsule with subtenon space block.[7] Other nomenclature for subtenon block includes parabulbar, pinpoint, or medial episcleral block.[8] The use of subtenon block is on the increase because of its simplicity and avoidance of needle insertion into the orbit associated with reported low complication rates, high patient satisfaction coupled with adequate anesthesia.[7],[9] Each technique has its own risk/benefit profile and proven to be highly successful if performed correctly. The choice of the technique should be individualized based on specific needs of the patient, nature and extent of eye surgery, and anesthesiologist's and surgeon's preferences and skill.[3]

The incidence of intraoperative and postoperative pain after regional ophthalmic block has been reported to be 13% and 37%, respectively.[5] The presence of pain during and after cataract surgery has been associated with lower patient's satisfaction with their anesthesia.[5]

The incidence of postoperative nausea or vomiting after regional ophthalmic block was 4.1%.[10] The complications which may follow ophthalmic block have been divided into sight and life-threatening events.[10] Such complications include corneal abrasion, chemosis, subconjunctival hemorrhage, vitreous hemorrhage, retrobulbar hemorrhage, globe penetration, and perforation.[10],[11] Others are extraocular muscle damage, inadvertent intravenous or intrathecal injection, local anesthetic agent toxicity, brainstem anesthesia, and cardiorespiratory arrest.[9],[10] Subconjunctival hemorrhage and chemosis are not uncommon after subtenon block with an incidence of 7%–100%.[8],[11] In 2011, subtenon block was introduced at our institution in accordance with approved standard of care for ophthalmic regional anesthesia.[7],[8] In an attempt to improve the quality of ophthalmic anesthesia and outcome following cataract surgery, we investigated the effect of peribulbar and subtenon block on pain and patients' satisfaction following SICS.

Setting

The study was conducted at the Guinness Eye Centre of the Lagos University Teaching Hospital, a 760-bed hospital located at Idi-Araba, Lagos


  Patients and Methods Top


The study spanned from November 2012 to October 2014. The Institutional Human Research Ethics Committee approval and individual participant informed consent were obtained. The American Society of Anesthesiologist Physical status (ASA) I-III patients aged 18 years and above scheduled for SICS were recruited. The exclusion criteria included patients with known sensitivity to lidocaine, previous eye surgery, eye injury or inflammation in the eye of interest, pupillary size less than 5 mm intraoperatively; failure to understand the numeric rating scale, patients who had planned or unplanned extracapsular cataract extraction, and those that declined to participate at any time. The preoperative review was done 24 h before surgery by both the ophthalmologist and anesthetist. During the visit, detailed information on the research protocol, consent form administration, pain assessment score using numeric rating scale, comfort score, and satisfaction score were explained to each participant. Routine investigations included packed cell volume, electrolytes, urea, and creatinine. Clinically controlled hypertensive and diabetic patients received their medication on the morning of surgery. For diabetic patients, the fasting blood sugar level was measured on the morning of surgery with OneTouch Glucometer (Life Scan, Inc. 2005 Milpitas, California USA), and patients with glucose level within the normal range (3.5–5.6 mmol/L) were recruited. Consecutive patients scheduled for SICS were allocated into the peribulbar (P) and subtenon (ST) block groups, respectively, depending on the patients need and ophthalmologist evaluation.

On arrival in the operating room, multiparameter patients monitor (Datex Ohmeda Cardiocap 710, Metropolitan Medical Services of NC. Inc., 15 Westside Drive, Asheville North Carolina, USA) was attached. Oxygen saturation, electrocardiogram, and noninvasive blood pressure were monitored continuously every 10 min till the end of surgery. Intravenous access was established with appropriate-sized cannula. All patients received 0.9% normal saline as per the standard protocol. All ophthalmic nerve block (subtenon or peribulbar anesthesia) was performed under strict asepsis by consultant ophthalmologists with at least 3 years' experience in SICS and regional block.

Technique of peribulbar block

The eyelid and periocular areas of the eye to be operated upon were cleaned with 5% povidone iodine after which the patient was instructed to look straight up to put the eye in the primary position of gaze. Thereafter, the inferior orbital rim was palpated and a 23-gauge, 1/4 long needle attached to a 5 ml syringe containing anesthetic solution was inserted through the eyelid skin at the junction of the medial two-third and the lateral one-third of the inferior orbital rim with the bevel of the needle facing up. The needle was advanced parallel to the floor of the orbit and tangential to the eyeball until the hub touched the skin. Thereafter, 4 ml of 2% lidocaine mixed with 1:1,000 adrenaline and 75 IU/ml hyaluronidase was injected after ensuring a negative aspiration for blood. After the injection, digital compression of the eyeball was done for 10 min to aid the dispersion of the anesthetic agent during which akinesia of the eyeball was assessed every 2 min. Ocular compression was discontinued and patient released for surgery if significant akinesia was achieved before 10 min. However, if significant akinesia was not achieved after 10 min of injection, 2 ml of supplemental injection was given between the caruncle and the medial canthus to a depth of 20 mm after which digital ocular compression was done for another 5 min.[11],[12]

Akinesia was assessed by one of the anesthetists who have previously been trained to measure the extent of ocular motility in the superior, inferior, nasal, and temporal quadrants with the aid of a transparent ruler using the limbus of the respective quadrant as a landmark. Movement of ≤2 mm or no movement from the primary position of gaze in three or more quadrants was regarded as “significant akinesia” while larger ocular movement (>2 mm) in two or more quadrants was regarded as “no significant akinesia” necessitating supplemental injection.[11],[12]

Technique for subtenon space block

Two drops of tetracaine (0.5%) eye drops were instilled into the eye to be operated upon after which the patient was asked to close the eye for 3 min. The eyelid and periocular areas were then cleaned with 5% povidone iodine after which a wire speculum was inserted to part the eyelids and ensure a good ocular exposure. Thereafter, the patient was asked to look superotemporally to expose the inferonasal quadrant. The inferonasal conjunctiva and tenon capsule were picked up with a Moorefield forceps and a small incision was made 5 mm from the limbus with a Westcott scissors. A blunt dissection of the tenon capsule was done with the scissors to expose the sclera and a 19-gauge, 2.54-cm long and curved subtenon cannula with a blunt tip was inserted following the curvature of the globe. Four milliliters of 2% lidocaine mixed with 1:1,000 adrenaline and 75 IU/ml hyaluronidase was injected. After the injection, digital compression of the eyeball and assessment of akinesia was done as described above. Two milliliters of supplemental injection was given through the same route in patients with “no significant akinesia” after 10 min of the initial injection. The study outcome was assessed by the anesthetist a coinvestigator, who was not involved with the regional block or surgery.[8],[11],[12]

Pain assessment

The pain and outcome were assessed by one of the anesthesiologists. A 10-point numeric rating scale (0–10) was used for pain assessment during surgery (during subconjunctival injection of antibiotics and steroid) and at specific intervals in the postoperative period (30 min and 1, 2, 4, and 24 h). If the patient complained of pain more than once during or after surgery, only the most severe was taken into consideration to determine the severity of pain. No pain was described as 0, mild pain <5, and moderate-to-severe postoperative pain (score ≥5). Patients who experienced moderate-to-severe postoperative pain (score ≥5) received oral paracetamol 1000 mg; if the pain persisted thereafter, oral diclofenac 100 mg was administered.

The patients' comfort and satisfaction score of the regional anesthetic technique were documented immediately after surgery.

The primary outcome measure was the occurrence and severity of intraoperative and postoperative pain following SICS. The secondary outcome measures were the occurrence of anesthetic complications and the degree of patients' satisfaction following SICS.

For this study, the following definitions were used

Postoperative complications included postoperative pain, postoperative nausea and vomiting, subconjunctival hemorrhage and chemosis.

Sight-threatening hemorrhage defined as hyphema, vitreous hemorrhage, subterinal hemorrhage, and moderate-to-severe choroidal hemorrhage.[13]

Patient comfort score

  1. Complete absence of sensation in the operated eye
  2. Sensation of the eye only such as irritation, but with no discomfort present
  3. Mild discomfort, but with the patient declining any offer of further analgesia or with no obvious clinical need for such further intervention
  4. Patient expresses wish for additional analgesia or exhibits an obvious clinical need for such intervention such as a state of distress related to pain on further questioning or requested for pain relief.[14],[15]


Patient satisfaction with anesthesia score (verbal)

  1. Very dissatisfied
  2. Slightly dissatisfied
  3. Neither satisfied nor dissatisfied
  4. Satisfied.[15]


Statistical analysis

Sample size calculation

Using a previous study [9] with difference in the peribulbar (Group P) and subtenon (Group ST) proportion of 20% suggesting no painful episode of 40% and 60%, respectively, with assumed attrition rate of 15% and ratio 1:2, 156 subjects (Group P) and 312 subjects (Group ST) to be able to reject the null hypothesis that the population proportion of Group P and Group ST was equal with probability (power) 90% and significance level of 0.05.

Statistical analysis was performed with the IBM SPSS software version 22. Data were presented as mean ± SD, median (IQR), frequency, and percentile, and the comparison between the groups was determined with the students' independent t-test for continuous and Chi-Square for categorical variables. A P ≤ 0.05 was considered significant.


  Results Top


A total of 462 patients were studied; 11 (2.38%) out of 462 patients had bilateral cataract extraction performed, while 226 (48.92%) and 225 (48.70%) were operated on the right and left eye, respectively. The M:F ratio in Group P was 1.2:1 and Group ST (1.2:1), P = 0.30. Among 207 (44.81%) patients with systemic comorbidities; hypertension was the most common disease in 149 patients (71.98%), followed by hypertension and diabetes in 27 (13.04%) patients [Table 1].
Table 1: Patients characteristics

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The mean duration of surgery was comparable; Group P (28.25 ± 17.16) minutes versus Group ST (26.98 ± 16.07) minutes, P = 0.66. The incidence of intraoperative pain in the two groups was comparable; Group P (8.67%) versus Group ST (7.05%), P = 0.66. A similar observation was made with postoperative pain Group P (53.3%) versus Group ST (47.1%), P = 0.308. However, the onset of postoperative pain was significantly shorter in peribulbar group (17.50 ± 14.43) minutes than in the subtenon group (74.92 ± 64.27), P < 0.001 [Table 1].

The median numeric rating scale (NRS) for pain was significantly higher during surgery, at 30 min, and 1 h after surgery in the peribulbar group than the subtenon group, P < 0.05. However, at 2, 4, and 24 h, there was no significant difference in the pain score [Table 2].
Table 2: Distribution of numeric rating scale between peribulbar and subtenon groups

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A higher number of patients in the peribulbar group 3 (2%) than the subtenon group 0 (0%), P = 0.034, required oral diclofenac in addition to paracetamol [Table 3].
Table 3: The distribution of pain and rescue analgesia

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Concerning patients comfort, more patients in subtenon group had complete absence of pain (93.2%) than peribulbar group (87.97), P < 0.001. 0.32% in the subtenon group required additional anesthesia compared with 7.33% in peribulbar group [Table 4]. However, more patients in peribulbar group (98%) were satisfied with their block than (96.2%) in subtenon group, P < 0.001, [Table 4].
Table 4: Comfort score and satisfaction level

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Concerning the extent of akinesia more patients in the peribulbar group 10 (6.67%) required additional anesthesia than the subtenon group 1 (0.32%), P < 0.001. Subconjuctiva hemorrhage and chemosis were more frequent with subtenon block; though no patient had retrobulbar hemorrhage, globe perforation and globe penetration in our cohort [Table 5].
Table 5: The distribution of complications after regional block

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  Discussion Top


In the present study, subtenon block was found to be more effective in the management of intraoperative and postoperative pain during cataract surgery than peribulbar block. This is because more patients in the subtenon group compared with the peribulbar group had a median numeric rating scale (NRS) less than 5 for pain intraoperatively. Likewise, the maximum NRS was lower in the former than the latter group. Our observation is in keeping with previous reports that the pain score for subtenon block is usually low, except for occasional outliers.[8] The quality of block was better with subtenon block than peribulbar block in our study. This is because complete absence of sensation in the operative eye was noted in more patients in the subtenon block group compared with the peribulbar block group. It was also observed that only one patient in the former compared with ten in the latter group did not have significant akinesia after the first injection necessitating supplemental injection. A similar observation was made by Datti et al.[16] in relation to pain score, however; the occurrence of akinesia was comparable.[16] They observed that there were more patients in the subtenon group who developed subconjunctival hemorrhage and chemosis, unlike peribulbar group with higher number of ptosis.[16] In addition, a lower volume of anesthetic agent and shorter duration of surgery was required in subtenon block. They concluded that subtenon block is a better alternative to peribulbar in manual SICS.[16]

In a study that compared the quality of analgesia between topical, retrobulbar, and subtenon's techniques. The authors observed that a higher proportion of patients in the subtenon's group had complete intraoperative analgesia compared to retrobulbar and topical groups.[10] The superior effect of subtenon block on quality of anesthesia, and analgesia was also illustrated when it was compared with either retrobulbar,[3],[8],[10] topical block,[13] or peribulbar block,[11],[12],[17] This observation may suggest that subtenon block provides better anesthesia and analgesia for cataract surgery than peribulbar block.

The incidence of intraoperative and postoperative pain is comparable between the groups in our study. However, the proportion of patients with intraoperative pain was lower in the subtenon (7.05%) group than in the peribulbar (8.67%). In a similar study, 6 patients (7.9%) had moderate pain in the peribulbar group while only 2 patients (2.6%) experienced moderate pain in the subtenon group.[12] The proportion of intraoperative pain is, however, lower than 13% reported during regional ophthalmic blocks.[4] Similarly, fewer patients in the subtenon group (47.12%) experienced postoperative pain when compared with the peribulbar block (53.33%). This is in agreement with a previous study, in which the proportion of patients with postoperative pain was less with subtenon block.[12] However, the frequency in the two groups was higher than 35% reported for regional ophthalmic blocks in a similar study.[4] The heterogeneity in the incidence of pain may not be unrelated to differences in patients' cohort, pain assessment, choice of local anaesthetic agent and volume. The use of rescue paracetamol and diclofenac in the postoperative period was commoner with peribulbar block in our study.

On the contrary, Al-Yousuf [18] observed that intraoperative pain perception was similar in both groups; however, the subtenon block reduced ocular movement during surgery.[18] The author concluded that subtenon anesthesia is more effective in terms of ocular movement than peribulbar anesthesia. Similarly, Mushtaq et al.[19] reported no significant difference in pain during and 4 h after surgery between subtenon and peribulbar block. It is important to note that the sample size in their studies was relatively small, which may influence the observation, unlike in other studies with a larger population.[4],[8] However, both researchers [18],[19] agreed that subtenon anesthesia is safe, and as effective as peribulbar anesthesia and is more comfortable to the patient at the time of administration.[18],[19]

The observed patient satisfaction level in our study was lower with subtenon block compared with peribulbar block. This is contrary to previous documentations that subtenon provides better patients' satisfaction than peribulbar block.[9],[10],[11] This may be because, in our study, the level of satisfaction was conducted immediately after the cataract extraction. In the subtenon block, 5.5% had painful sensation in the eye, and 1.3% had mild discomfort compared with 4.7% and 0%, respectively, in the peribulbar block group during the operation. This was in contrast to previous observations that subtenon provided better patients satisfaction compared with peribulbar, retrobulbar, and topical block.[9],[10],[11] Another study that subtenon's blocks with retrobulbar block.[9] The authors observed that over 68% of patients had no discomfort at all during performance of the block and less than 1.5% reported more than mild to moderate pain.[9]

The rate of subconjuctival hemorrhage and chemosis was higher with subtenon block than peribulbar block; nevertheless, the rates were lower than 10% in both groups. Similar observation was documented by Iganga et al.[12] although the proportions were slightly more than 40% for the subtenon's group.

In a group of cardiac patients on warfarin who had cataract surgery under peribulbar and subtenon technique,[13] the frequency of hemorrhage was significantly higher in the subtenon group than the peribulbar group.[13] However, the proportions of patients with subconjuctival hemorrhage was similar, and there was no sight threatening hemorrhagic complications. Pain was significantly lower in the subtenon's group. A majority of the patients reported satisfaction.[13] The surgeons, however admitted a significantly higher satisfaction with peribulbar than subtenon block.[13] The authors recommended the use of peribulbar block in patients on anticoagulants since the frequency of hemorrhage was less. The higher frequency of hemorrhage in the latter study when compared to the present study may be related to the use of anticoagulants by the patients.

In the present study, no patient developed sight threatening hemorrhage, globe penetration, or perforation. This was similar to the observations made by other researchers.[12],[13] This is not surprising as it has previously been reported that the complication following subtenon is usually minor, which include pain upon injection, reflux of local anesthetic, chemosis, and conjunctival hemorrhage with varying incidence.[7] Our finding was in agreement with a study in the United Kingdom, where it was noted that the incidence of sight-threatening complications was lower with subtenon than the other blocks; subtenon block (0.6/10,000) versus peribulbar (2.9 per 10,000) versus retrobulbar techniques (4.5 per 10,000).[9] Another study reported a 60% reduction in the incidence of serious complications with subtenon (12 per 10,000) compared to peribulbar anesthesia (5/10,000).[17] However, minor complications in the subtenon group such as chemosis (2.03%) and subconjunctival hemorrhage (1.99%) were more common than in the peribulbar group.[17] They concluded that subtenon block is continuing to gain popularity and is now the most popular technique of regional orbital anesthesia in many centers. It also provided extremely good analgesia and operating conditions, while avoiding the passage of sharp needles into the orbit.[19] It has been reported that the risk of serious complications with subtenon block is very low, and studies have shown that their incidence is much lower than with other techniques of ocular regional anesthesia.[8]

The occurrence of postoperative nausea and vomiting is low with either subtenon (nausea 0% and vomiting 1.3%) or peribulbar (nausea 1.33% and vomiting 1.33%) in the present study. This is the general trend with postoperative nausea and vomiting after local ophthalmic blocks.[15]

This study is limited by the fact that the block was performed by three different consultant ophthalmologists whose competence was comparable with respect to the peribulbar and subtenon block as well as SICS. In addition, the study was not randomized which may have resulted in selection bias.


  Conclusion Top


The use of subtenon block resulted in lower intraoperative and postoperative pain scores and higher patients' comfort than peribulbar block. However, subconjuctival hemorrhage and chemosis were more common with subtenon block. We recommend the use of subtenon block for SICS in low-risk patients, while in patients on anticoagulants, peribulbar block is recommended since the frequency of hemorrhage was less. There will be need for further randomized controlled study.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

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Ryu JH, Kim M, Bahk JH, Do SH, Cheong IY, Kim YC, et al. A comparison of retrobulbar block, sub-tenon block, and topical anesthesia during cataract surgery. Eur J Ophthalmol 2009;19:240-6.  Back to cited text no. 2
    
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Srinivasan S, Fern AI, Selvaraj S, Hasan S. Randomized double-blind clinical trial comparing topical and sub-tenon's anaesthesia in routine cataract surgery. Br J Anaesth 2004;93:683-6.  Back to cited text no. 4
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Katz J, Feldman MA, Bass EB, Lubomski LH, Tielsch JM, Petty BG, et al. Injectable versus topical anesthesia for cataract surgery: Patient perceptions of pain and side effects. The study of medical testing for cataract surgery study team. Ophthalmology 2000;107:2054-60.  Back to cited text no. 11
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Iganga ON, Fasina O, Bekibele CO, Ajayi BG, Ogundipe AO. Comparison of peribulbar with posterior sub-tenon's anesthesia in cataract surgery among Nigerians. Middle East Afr J Ophthalmol 2016;23:195-200.  Back to cited text no. 12
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Rizk SN, Fahim MR, El-Zakzouk ES. Peribulbar versus subtenon block in cardiac patients undergoing cataract surgery during warfarin therapy. Egyp J Anaesth 2014;30:225-59.  Back to cited text no. 13
    
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Matcha SC, Nandyala SKK, Murahari VK. Comparison of subtenon V/S Peribulbar anesthesia in manual small incision cataract surgery cases. MRIMS J Health Sci 2015;3:68-70.  Back to cited text no. 14
    
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    Tables

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5]



 

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