About MEAJO | Editorial board | Search | Ahead of print | Current Issue | Archives | Instructions to authors | Online submission | Subscribe | Advertise | Contact | Login 
Middle East African Journal of Ophthalmology Middle East African Journal of Ophthalmology
Users Online: 1185   Home Print this page Email this page Small font sizeDefault font sizeIncrease font size

  Table of Contents 
Year : 2016  |  Volume : 23  |  Issue : 2  |  Page : 195-200  

Comparison of peribulbar with posterior sub-tenon's anesthesia in cataract surgery among Nigerians

1 Department of Ophthalmology, University College Hospital, Ibadan, Nigeria
2 Department of Ophthalmology, University of Ibadan/University College Hospital, Ibadan, Nigeria

Date of Web Publication5-Apr-2016

Correspondence Address:
Oluyemi Fasina
Department of Ophthalmology, University of Ibadan/University College Hospital, Ibadan
Login to access the Email id

Source of Support: None, Conflict of Interest: None

DOI: 10.4103/0974-9233.164609

Rights and Permissions

Purpose: To compare the akinetic and the analgesic effects of peribulbar and posterior sub-Tenon's anesthesia in patients undergoing cataract surgery.
Methods: In a hospital-based randomized comparative interventional study, patients aged 50 years and above who underwent elective surgery for uncomplicated cataract were randomized to receive either peribulbar block or posterior sub-Tenon block. Pain during injection, surgery, and after surgery was assessed using numerical reporting scale (NRS). Limbal excursion was measured with a transparent meter rule.
Result: A total of 152 eyes of 152 patients were studied. Peribulbar and sub-Tenon regional blocks provided comparable adequate akinesia (P = 0.06) and similar levels of analgesia (P = 0.10) during cataract surgery. Both techniques also provided similar levels of analgesia to the patient during injection and in the immediate postoperative period. Ninety-two percent of patients who had peribulbar and 97% of those who had sub-Tenon blocks reported either mild pain or no pain at all during surgery (P = 0.49). There was no report of severe pain in all patients during the stages of the surgery. Occurrence of chemosis and subconjunctival hemorrhage was more common in sub-Tenon than peribulbar anesthesia.
Conclusions: This study shows that peribulbar and posterior sub-Tenon routes of administering anesthetic substances is comparable in providing adequate akinesia and analgesia for cataract surgery with minimal complications. Therefore, both techniques are effective and safe for cataract surgery among Nigerians.

Keywords: Extracapsular Cataract Surgery, Manual Small Incision Cataract Surgery, Nigeria, Peribulbar Anesthesia, Posterior Sub-Tenon′s Anesthesia

How to cite this article:
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

How to cite this URL:
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 [serial online] 2016 [cited 2022 Dec 9];23:195-200. Available from: http://www.meajo.org/text.asp?2016/23/2/195/164609

   Introduction Top

Local anesthesia involves the blockage of a nerve supplying a given part of the body by infiltration of the area around the nerve with a local anesthetic agent. [1] The use of local anesthesia in cataract extraction has increased over the years. This is due to advances in drugs, surgical instruments such as use of blunt sub-Tenon cannula and modification of techniques and routes of administration. [2] Some of its merits include ease of administration, preservation of consciousness, good postoperative analgesia, reduced stress response, early mobilization, and discharge of patients as well as minimal respiratory and cardiovascular systems complications. [2],[3],[4],[5] Regional anesthesia has been popularized in ophthalmic surgery because of its high success rate and a wide margin of safety. [4] It ensures quicker patient recovery thereby enabling day-surgery cases and reduction in cost of surgery. [6]

Multiple co-morbidities and multiple drug use are very common in cataract patients. [7] Therefore, researchers have focused on anesthetic techniques for cataract surgery that ensure patients' safety, comfort, and attain optimum safe conditions for the surgical procedure. [6]

Retrobulbar block was hitherto the mainstay of local anesthesia for cataract surgery. [8] It has a fast onset of action with a small volume of anesthetic agent required. However, it is associated with vision and life-threatening complications. Some of these complications include retrobulbar hemorrhage, globe perforation and brainstem anesthesia. [9],[10] Peribulbar anesthesia was developed as a potentially safer option. However, it has a slower onset of akinesia, requires larger volume of anesthetic agent and higher rate of supplementation. [11],[12],[13],[14],[15] Serious complications such as retrobulbar hemorrhage, globe perforation, and brainstem injection have also been reported following peribulbar injections. [9],[16] To avoid these complications, needle-free procedures such as sub-Tenon and topical as well as topical with intracameral anesthesia were developed.

   Methods Top

The study was carried out in the Department of Ophthalmology University College Hospital and St. Mary's Catholic Eye Institute, Eleta both in Ibadan, Nigeria. Ethical approval was obtained from University of Ibadan/University College Hospital Joint Ethics Committee.

All patients were aged 50 years and above and were scheduled for elective surgery for uncomplicated cataract under local anesthesia. Written informed consent was obtained from each patient after a detailed explanation about the conduct of the study. The study followed the tenets of Helsinki declaration.

One hundred and fifty-two patients; 76 in each arm was studied. Each patient was randomly allocated to either group A (peribulbar block) or group B (posterior sub-Tenon block) using a computer-generated block of four random numbers with an epitable software. [17] All anesthetic injections were administered by one the authors (ION) who also assessed the complications of the procedures. Pain and globe akinesia were assessed by an independent assessor. The patient, the independent assessor and the surgeons were masked to the type of anesthesia administered.

The patients underwent either manual small incision cataract surgery (MICS) or extracapsular cataract extraction with intraocular lens implantation.

Posterior sub-Tenon's anesthesia

Tetracaine 0.5% eye drops was instilled into the eye to be operated on. The patient was instructed to close the eye for 2 min and timed with the stop clock. The eyelids and periocular area were subsequently cleaned with 5% povidone iodine. Eyelid wire speculum was inserted to gain good exposure and the patient was instructed to look upward and outward to expose the inferonasal quadrant. The conjunctiva was lifted up in the inferonasal quadrant with Moorfields forceps. A small conjunctival nick was made with a blunt Westcott's scissors 5 mm from the limbus and a blunt dissection into the sub-Tenon space was made to expose the sclera. To minimize subconjunctival hemorrhage, any visible blood vessel was avoided. A 19G curved posterior sub-Tenon cannula attached to 5 ml syringe containing anesthetic injection was inserted into the sub-Tenon space glided along the contour of the globe. Five milliliters of 2% lignocaine mixed with adrenaline 1:200,000 (5 μg/ml) and hyaluronidase 150 IU/ml was injected slowly into the sub-Tenon space. In a situation where there was resistance in injecting anesthetic, the direction of the cannula was changed.

Peribulbar anesthesia

The eyelid and periocular areas were cleaned with 5% povidone iodine. The patient was instructed to look straight ahead to ensure that the eye was in the neutral position of gaze. The injection was given at the inferotemporal site using 1 [1]/[4] -inch 23 gauge sharp needle attached to 5 ml syringe containing the anesthetic agent with the eye in neutral position of gaze. The needle was inserted through the lid as lateral as possible toward the junction of the inferior orbital rim and the lateral margin parallel to the floor of the orbit and tangential to the globe. The needle was advanced until the hub touched the skin. After negative aspiration for blood, 5 ml of lignocaine 2% mixed with adrenaline 1:200,000 (5 μg/ml), and hyaluronidase 150 IU/ml was injected. The eye was massaged digitally for between 5 and 10 min.

Appropriate supplemental anesthetic injection was given through the medial canthal route to any participant in either group where needed.

Assessment of pain

An 11-point (0-10) numerical pain reporting scale (NRS) [18] was used to assess patient-reported pain during injection of anesthesia, intraoperatively and postoperatively by the independent assessor. NRS is a linear scale subdivided into 10 equal intervals, with the left end marked 0, indicating no pain, and the right end marked 10, representing the worst pain imaginable. Patient-reported pain during administration of anesthesia, during surgery, and after surgery was recorded as none, mild, moderate, or severe with none defined as a score of zero on the 11-point scale, mild as 1-3, moderate as 4-6, and severe as more than 6. The chart was explained to the patients after randomization. The patients were asked to grade the pain experienced during the injection of the anesthetic on the NRS before massaging was done. The patient was asked to grade the intraoperative pain on the NRS during the surgery after insertion of the intraocular lens. The postoperative pain was assessed within 5 min after surgery as soon as the patient got to the recovery room using the same scale.

Assessment of motility

Measurement of ocular movement in all four quadrants (inferior, superior, medial, and lateral) was performed using a transparent plastic rule by the independent assessor who was not aware of the anesthetic technique used. The reference point was the limbus of the appropriate quadrant. The patient was instructed to look in the primary position of gaze where possible. The zero mark of the rule was aligned with the limbus of the appropriate quadrant and patient instructed to look toward that quadrant and the extent of limbal excursion in that direction read off from the rule. Excursion was scored as follows, (0) no movement, (1) movement of 2 mm and (2) movement of more than 2 mm. Overall movement score was obtained by combining the scores of these four directions of movement. This score ranges from 0 (no movement) to 8 (complete movement) and was categorized into two groups, akinesia (score 0-4) and no akinesia (score 5-8). The motility was assessed every 2 min until akinesia was attained or up to 10 min after the injection of anesthesia if otherwise. The serial measurement was terminated once akinesia was attained. Supplemental injection was given if akinesia was not achieved at 10 min.

Statistical analysis

Data collected were entered into a database and analyzed with Statistical Package for Social Sciences (SPSS) version 20 (SPSS Inc., Chicago, Illinois, USA). Data were cleaned and mean values as well as standard deviation were generated to get a pattern of variability between anesthetic procedures. Results are presented in frequency tables, charts, means, and rates. Chi-square and Student's t-test was used to test for association between qualitative and continuous variables, respectively. P <0.05% was considered statistically significant.

   Results Top

One hundred and fifty-two eyes comprising 77 right eyes and 75 left eyes of 152 respondents were studied. There was no statistically significant difference either in eyes operated on (P = 0.87) or in the gender distribution (P = 0.38) of the respondents. The age range of the respondents was 50-91 years with a greater proportion aged between 60 and 80 years. The mean ages were 68.16 ΁ 9.61 and 69.46 ΁ 8.85 years for peribulbar and posterior sub-Tenon blocks respectively.

A statistically significant proportion of patients who received peribulbar block achieved akinesia at 8 min (P = 0.03) and 12 min (P = 0.01) compared to posterior sub-Tenon, However, overall, there was no significant difference (P = 0.06) in the globe akinesia between the two groups [Figure 1].
Figure 1: Akinesia score of 0-4 against time in the patients

Click here to view

A large proportion (75% peribulbar vs. 82.9% posterior sub-Tenon) of the patients experienced mild pain during the injection of anesthesia. Six (7.9%) of patients had moderate pain in the peribulbar group while only two (2.6%) of patients experienced moderate pain in the sub-Tenon arm [Table 1]. No patient reported severe pain in either group. The mean pain score during injection was 1.45 and 1.37 for the peribulbar and posterior sub-Tenon techniques respectively which was not statistically significant (P = 0.64).
Table 1: Patient reported pain during injection of anesthesia

Click here to view

Sixty-six (86.8%) and three (4.0%) patients in the peribulbar group reported mild pain and moderate pain, respectively. Similarly, 66 (86.8%) and six (7.9%) patients in the posterior sub-Tenon group, respectively, reported mild and moderate pain. No patient reported severe pain during surgery in the two groups [Table 2]. The difference in the pain reported during surgery by the patients in the two groups was not statistically significant (P = 0.10).
Table 2: Patient reported pain during surgery

Click here to view

Fifty-four (71.1%) patients in peribulbar group reported no pain immediately after surgery compared to 53 (69.7%) in the sub-Tenon group. None of the respondents reported moderate or severe pain in either group. There was no statistically significant difference (P = 0.88) in pain perception between the two groups [Table 3].
Table 3: Patient reported pain immediately after surgery

Click here to view

Thirty-three (43.4%) and 15 (19.7%) respondents in the posterior sub-Tenon and peribulbar groups, respectively, had chemosis. The posterior sub-Tenon group significantly had more chemosis than the peribulbar arm (P = 0.005) [Table 4].
Table 4: Occurrence of some complications in both groups of patients

Click here to view

Thirty-two (42.1%) patients in the posterior sub-Tenon group compared with three (3.9%) patients in the peribulbar group had subconjunctival hemorrhage and this was statistically significant (P = 0.00) [Table 4]. No case of retrobulbar hemorrhage or globe perforation was observed in either group.

   Discussion Top

Globe akinesia (score of 0-4) was achieved in both groups at 2 min after injection in a significant proportion (63% in the peribulbar and 70% posterior sub-Tenon anesthetic injection) of the respondents. The proportion of patients that achieved akinesia increased with time. The two anesthetic techniques were comparable in providing globe akinesia for cataract surgery (P = 0.06). This is in agreement with some authors [17],[19],[20] who reported that sub-Tenon block was comparable to peribulbar block in providing adequate globe akinesia and anesthesia for cataract surgery. Some other studies, [21],[22],[23] however, reported that sub-Tenon block provided a better globe akinesia than peribulbar anesthesia during surgery. In these studies, [17],[20],[21] different volumes of the anesthetic agent were used for the peribulbar and posterior sub-Tenon groups while in the present study, equal volumes were given in both groups. The different volumes of anesthetic agents used may account for the variation. However, in another study Al-Yousuf [21] in Bahrain used equal volumes of the same anesthetic mixture in both groups and reported that the sub-Tenon's anesthesia was more effective in achieving globe akinesia compared to peribulbar anesthesia. However, he did not state the time interval for grading the akinesia.

The number of patients who received supplementary injection was statistically significantly higher in peribulbar group compared to the sub-Tenon's anesthesia (P = 0.02). Eighty-seven percent and 100% of respondents who received supplementary injection in the peribulbar and sub-Tenon groups respectively were given 2-3 ml. The average volume of supplementary anesthetic injection for peribulbar group was 3 ml (range 2-10 ml) while that of sub-Tenon was 2 ml (range 2-3 ml). The volume of top up injection was individualized according to the level of akinesia achieved at 10 min. This was given once except in two patients in the peribulbar group who received 5 ml and 10 ml each in two divided volumes. This suggests that higher volume of supplementary injection of same mixture of anesthetic agent might be needed in peribulbar compared to sub-Tenon's anesthetic injection. Similar studies [17],[20],[22] also reported that significantly higher number of patients who received peribulbar anesthesia were given supplementary injection compared to sub-Tenon group.

A high proportion of the patients reported mild pain in both groups during anesthetic injection, (75% in peribulbar vs. 83% in the sub-Tenon group, P = 0.64) and during surgery (87%), while a small proportion reported moderate pain during injection and surgery. There was no report of severe pain at any stage of the surgery in both groups while a high proportion of patients (71% peribulbar vs. 70% posterior sub-Tenon group, P = 0.88) reported no pain immediately after surgery. There have been similar reports in studies done by Azmon et al. [19] in Israel, Budd et al. [20] in the United Kingdom, Parkar et al. [17] in India and Al-Yousuf [21] in Bahrain that both techniques caused the patients similar level of pain during administration and intra-operatively. However, in another study, Briggs et al. [24] in the United Kingdom reported that more patients experienced pain during peribulbar injection compared to sub-Tenon's anesthetic injection (P < 0.05). Overall, there was no difference in the pattern of patient reported pain between the two techniques during injection of anesthesia, surgery and in the immediate postoperative period, suggesting that both techniques provided a similar level of comfort to the patients at each stage of the surgery.

The incidence of chemosis was found to be significantly higher (P = 0.005) in the sub-Tenon technique compared to the peribulbar group in this study. Budd et al. [20] and Parkar et al. [17] however, found no difference in the incidence of chemosis between sub-Tenon and peribulbar anesthesia. Probably the injection was deposited into wrong anatomical planes such as mid sub-Tenon space in some presumed cases of posterior sub-Tenon injection. Incidence of chemosis and subconjunctival hemorrhage increases with injection into anterior and mid sub-Tenon spaces compared to posterior sub-Tenon space. [25] Although equal volume arm was used in both peribulbar and posterior sub-Tenon groups, the closeness of the sub-Tenon space to the subconjunctival space may also have accounted for higher rate of chemosis in the latter. This study equally revealed statistically significant higher (P = 0.00) rate of subconjunctival hemorrhage in the sub-Tenon technique compared to the peribulbar technique. Budd et al. [20] also reported that it was significantly higher in sub-Tenon group compared to peribulbar group. This may be due to severance of the subconjunctival vessels during dissection into the sub-Tenon space. These complications, however, did not lead to cancellation of any surgery in the study.

No life or sight-threatening complications such as globe perforation, retrobulbar hemorrhage, optic nerve injury, central retinal vessel occlusion or brainstem anesthesia were recorded. This is similar to findings in other studies. [17],1[8],[19],[20],[21],[22],[23]

This study shows that peribulbar and sub-Tenon routes of administering anesthetic substance are comparable in providing adequate akinesia and analgesia for cataract surgery among Nigerians. Both anesthetic blocks caused mild pain during injection, but provided comparable good analgesia during surgery and in the immediate postoperative period. The occurrence of chemosis and subconjunctival hemorrhage though significantly higher in the sub-Tenon group compared to peribulbar group did not result in cancellation of any surgery. There was no life- or sight-threatening complication recorded. This study, therefore, suggests that both techniques are effective and safe.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

   References Top

Alhassan MB, Kyari F, Ejere HOD. Peribulbar versus retrobulbar anaesthesia for cataract surgery. Cochrane Database of Systematic Reviews 2008, Issue 3. Art. No.: CD004083. DOI: 10.1002/14651858.CD004083.pub2.  Back to cited text no. 1
Lee A, Wildsmith JA. Local anaesthetic techiques. In: Aitkenhead AR, Smith G, editors. Textbook of Anaesthesia. 3 rd ed. London: Churchill Livingstone; 1996. p. 445-69.  Back to cited text no. 2
Barker JP, Vafidis GC, Robinson PN, Burrin JM, Hall GM. The metabolic and hormonal response to cataract surgery. A comparison between retrobulbar and peribulbar blockade. Anaesthesia 1993;48:488-91.  Back to cited text no. 3
McLure HA, Rubin AP. Local anaesthesia for ophthalmic surgery. Curr Anaesth Crit Care 1999;10:40-7.  Back to cited text no. 4
Biscoping J. Advantages of regional anesthesia over general anesthesia. In: Hoerster W, Kreusscher H, Niesel HC, Zenz M, editors, Dekornfeld TJ, trans. Regional Anesthesia. 2 nd ed. London: Mosby Year Book; 1990. p. 31-45.  Back to cited text no. 5
Malik A, Fletcher EC, Chong V, Dasan J. Local anesthesia for cataract surgery. J Cataract Refract Surg 2010;36:133-52.  Back to cited text no. 6
McKibbin M. The pre-operative assessment and investigation of ophthalmic patients. Eye (Lond) 1996;10 (Pt 1):138-40.  Back to cited text no. 7
Nouvellon E, Cuvillon P, Ripart J. Regional anesthesia and eye surgery. Anesthesiology 2010;113:1236-42.  Back to cited text no. 8
Gillow JT, Aggarwal RK, Kirkby GR. A survey of ocular perforation during ophthalmic local anaesthesia in the United Kingdom. Eye (Lond) 1996;10:537-8.  Back to cited text no. 9
Lau LI, Lin PK, Hsu WM, Liu JH. Ipsilateral globe penetration and transient contralateral amaurosis following retrobulbar anesthesia. Am J Ophthalmol 2003;135:251-2.  Back to cited text no. 10
Troll GF. Regional ophthalmic anesthesia: Safe techniques and avoidance of complications. J Clin Anesth 1995;7:163-72.  Back to cited text no. 11
Ripart J, Lefrant JY, de La Coussaye JE, Prat-Pradal D, Vivien B, Eledjam JJ. Peribulbar versus retrobulbar anesthesia for ophthalmic surgery: An anatomical comparison of extraconal and intraconal injections. Anesthesiology 2001;94:56-62.  Back to cited text no. 12
Rozentsveig V, Yagev R, Wecksler N, Gurman G, Lifshitz T. Respiratory arrest and convulsions after peribulbar anesthesia. J Cataract Refract Surg 2001;27:960-2.  Back to cited text no. 13
Wadood AC, Dhillon B, Singh J. Inadvertent ocular perforation and intravitreal injection of an anesthetic agent during retrobulbar injection. J Cataract Refract Surg 2002;28:562-5.  Back to cited text no. 14
Riad W, Akbar F. Ophthalmic regional blockade complication rate: A single center audit of 33,363 ophthalmic operations. J Clin Anesth 2012;24:193-5.  Back to cited text no. 15
Gillow JT, Aggarwal RK, Kirkby GR. Ocular perforation during peribulbar anaesthesia. Eye (Lond) 1996;10:533-6.  Back to cited text no. 16
Parkar T, Gogate P, Deshpande M, Adenwala A, Maske A, Verappa K. Comparison of subtenon anaesthesia with peribulbar anaesthesia for manual small incision cataract surgery. Indian J Ophthalmol 2005;53:255-9.  Back to cited text no. 17
[PUBMED]  Medknow Journal  
Deruddre S, Benhamou D. Medial canthus single-injection peribulbar anesthesia: A prospective randomized comparison with classic double-injection peribulbar anesthesia. Reg Anesth Pain Med 2005;30:255-9.  Back to cited text no. 18
Azmon B, Alster Y, Lazar M, Geyer O. Effectiveness of sub-Tenon′s versus peribulbar anesthesia in extracapsular cataract surgery. J Cataract Refract Surg 1999;25:1646-50.  Back to cited text no. 19
Budd JM, Brown JP, Thomas J, Hardwick M, McDonald P, Barber K. A comparison of sub-Tenon′s with peribulbar anaesthesia in patients undergoing sequential bilateral cataract surgery. Anaesthesia 2009;64:19-22.  Back to cited text no. 20
Al-Yousuf N. Sub-tenon versus peribulbar anaesthesia for cataract surgery. Bahrain Med Bull 2003;25:115-8.  Back to cited text no. 21
Ripart J, Lefrant JY, Vivien B, Charavel P, Fabbro-Peray P, Jaussaud A, et al. Ophthalmic regional anesthesia: Medial canthus episcleral (sub-tenon) anesthesia is more efficient than peribulbar anesthesia: A double-blind randomized study. Anesthesiology 2000;92:1278-85.  Back to cited text no. 22
Shahid E, Afaq A, Juzar UT, Ansari Z, Hasan KS. Sub-Tenon versus peribulbar anesthesia in phacoemulsification a comparative study. Int J Ophthalmol Eye Sci 2013;1 :9-13. Available from: http://www.scidoc.org/articles pdf/ijoes/IJOES-01-02.pdf. [Last accessed on 2013 Oct 05].  Back to cited text no. 23
Briggs MC, Beck SA, Esakowitz L. Sub-Tenon′s versus peribulbar anaesthesia for cataract surgery. Eye (Lond) 1997;11:639-43.  Back to cited text no. 24
Kumar CM, Dodds C, McLure H, Chabria R. A comparison of three sub-Tenon′s cannulae. Eye (Lond) 2004;18:873-6.  Back to cited text no. 25


  [Figure 1]

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

This article has been cited by
Matteo Ripa, Chiara Schipa, Nikolaos Kopsacheilis, Mikes Nomikarios, Carlo De Rosa, Pasquale De Rosa, Lorenzo Motta
Retina. 2022; 42(10): 1852
[Pubmed] | [DOI]
2 A comparative study of subtenonís anaesthesia with peribulbar anaesthesia for manual small incision cataract surgery in patients with age related cataracts
Gayatri Bhonsale, Ishita Mehta, Priyanka Hitesh Gandhi, Reshma Ramakrishnan, Syed Faraaz Hussain
Indian Journal of Clinical and Experimental Ophthalmology. 2022; 8(3): 409
[Pubmed] | [DOI]
3 A Comparative Study Between Single Medial Canthus Injection Using 13 x 0.45 mm Needle and Posterior Sub-Tenon Injection as Local Anesthesia Techniques for Strabismus Surgery in Adults
Norhan A. Sherif, Mayada K. Mohamad, Ahmed A. Hannon, Noha A. Osama
The Open Anesthesia Journal. 2020; 14(1): 8
[Pubmed] | [DOI]


    Similar in PUBMED
   Search Pubmed for
   Search in Google Scholar for
 Related articles
    Access Statistics
    Email Alert *
    Add to My List *
* Registration required (free)  

  In this article
    Article Figures
    Article Tables

 Article Access Statistics
    PDF Downloaded318    
    Comments [Add]    
    Cited by others 3    

Recommend this journal