This document discusses various techniques for providing anesthesia during ocular surgery, including retrobulbar, peribulbar, and sub-Tenon's blocks. Retrobulbar blocks involve injecting local anesthetic directly into the muscle cone behind the eyeball to block the oculomotor nerves. Peribulbar blocks inject anesthetic in the space surrounding the eye muscles. Sub-Tenon's blocks make a small incision in Tenon's capsule to inject anesthetic beneath it. Each technique has advantages and disadvantages in terms of onset/duration of anesthesia, risk of complications, and ability to achieve akinesia.

1. Moderator : DR. Padmajothi M S
Presenter: Dr. Darshan S M

2.  To assure safe surgical procedure by
achieving akinesia, anesthesia & apropriate
hypotony.

3.  Subperiosteal space : between the orbital bones
and the periorbita
 Peripheral orbital space (anterior space) : bounded
peripherally by periorbita and internally by 4 recti
 Central space (muscular cone or retrobulbar space):
Anteriorly :Tenon’s capsule
peripherally: 4 recti
posterior : continuous with peripheral space
 Sub-Tenon’s space: between sclera and tenon’s
capsule

5.  Topical anesthesia
 Local anesthesia

6.  Lidocaine 2%
> Onset of action : 5-10 mins
> Duration of action : 1-2hrs
 Bupivacaine 0.75%
> Onset of action : 15-30mins
> Duration of action : 5-10hrs

7. > minimise systemic absorption of
anesthetic agents
> prolong the duration of action
> minimise bleeding
> systemic effects may b harmfull.

8.  Enhances diffusion of anesthetic mixture
through tissues
 Use 75 units per 10ml anesthetic solution

9.  Lidocaine 2% with or without epinephrine
1:100,000 (5ml)
 Bupivacaine 0.75% (5ml)
 Hyaluronidase ( 75 units )
Therfore the final concentrations in the
anesthetic mixture are lidocaine 1%,
bupivacaine 0.37%, epinephrine 1:200,000
& hyaluronidase 7.5 units per ml

10.  The first modern use of topical anesthesia
was by Koller in 1884 with cocaine.

11.  Benoxinate 0.4%, an ester (commonest &
safest )
 Other agents : tetracaine 0.5% , 1%
amethocaine proparacaine (proxymetacaine)
0.5%; short acting (20 minutes) and are the
least toxic to the corneal epithelium.
 Lidocaine 4% and bupivacaine 0.5% and
0.75% have a longer duration of action but an
increased associated corneal toxicity

12.  To block the nerves that supply the
superficial cornea and conjuctiva
> long & short ciliary nerve
> nasociliary nerve
> lacrimal nerve

13.  The patient is asked to focus on the source
of the light
> Small sponge soaked with the drops can be
kept in the inferior and superior fornix or a
ring saturated with drops can placed in the
paralimbal region to maintain corneal
clarity

14. • No risk associated at needle insertion
• No risk of periocular hemorrhage
• Functional vision is maintained
• No postoperative diplopia or ptosis
• Patients are fully alert

15. • An awake and talkative patient can be
distracting for the surgeon
• No akinesia of the eye
• If difficulties or problems occur the
anesthesia may not be adequate

16.  Aim
to block the oculomtor nerves before
they enter the four muscles in the posterior
intraconal space.

17.  Local anesthetic is
delivered within the
muscle cone itself.
 Into Central space
 Using 22 G 35 mm
long needle
 In the Inferotemporal
quadrant
 At Junction of lateral
1/3rd and medial 2/3rd
of inferior orbital
margin

18.  4-5 ml of local anaesthetic agent
Bupivacaine 0.75% 5 ml
Lidocaine 2% 5 ml with adrenaline
Hyaluronidase 75 units/m

19.  Palpate inferior orbital rim.
 Place needle perpendicular through skin ,
locate needle 1/3rd distance from lateral to
medial canthus
 Place just superior to inferior orbital rim

20.  Inject 0.5ml of solution s/c to reduce pain
when orbital septum is pierced
 Advance needle parallel to orbital floor
perforating the septum
 After equater of globe is passed direct needle
superonasally at 30 degree angle , advance
,piercing intermuscular septum and enter
muscle cone,inject 4-5ml of anesthetic

23. • A retrobulbar block is reliable for producing
excellent anesthesia and akinesia
•The onset of the block is quicker than with
peribulbar; it usually occurs within 5 minutes
• Low volumes of anesthetic ,results in a lower
intraorbital tension and less chemosis than with
peribulbar blocks
• Loss of visual acuity occurs in a greater number
of patients compared to peribulbar blocks,
though this can be volume dependent

24.  The main disadvantage of retrobulbar
blocks is that the complication rate is
higher than for peribulbar blocks – the
reason for the development of the
peribulbar block

25.  There is a 1–3% chance that complications
will occur with retrobulbar block.
 Retrobulbar hemorrhage
 Ocular perforation (< 0.1% incidence, but 1
in 140 injections in myopic eyes)[
 Subarachnoid or intradural injection,
leading to brainstem anesthesia in 1 in 350–
500 patients

26.  Muscle complications: ptosis from levator
aponeurosis dehiscence, entropion and
diplopia following extraocular muscle
injection
 Oculocardiac reflex, usually produced by
pressure on the globe (vasovagal
bradycardias are more common)

27.  Most common ,due to inadvertant puncture of
vessels within retrobulbar space.
 Simultaneous appearance of an excellent motor
block of the globe, closing of the upper lid,
proptosis and a palpable increase in intraocular
pressure.
 It can lead to stimulation of the oculocardiac reflex.
 the best course of action to postpone surgery for 2-
4 days after hemmorhage

28.  Risk factors : High myopia (axial length
greater than 26 mm),
 Sharp injection needle
 Previous scleral buckling
 Inexperience in performing local blocks
 Poor patient compliance
 SIGNS: Sudden loss of vision,hypotonia,poor
red reflex

29.  The injection is outside the muscle cone
 Spreads by way of diffusion to block the
orbital nerves, including the IV nerve.
 25 G ,25 mm long needle
 Place needle perpendicular through skin
 Locate needle 1/3rd distance from lateral to
medial canthus

30.  1st injection
 Place just superior to the inferior orbital rim
 Advance parallel to orbital floor,peforating orbital
septum
 Hub of needle should not go beyond inferior orbital
rim.
 Aspirate to avoid blood vessel and inject 3ml of
anesthetic solution .
 Apply pressure to prevent hemorrhage and
facilitate diffusion of anesthetic

31.  2nd injection
 Locate needle by supraorbital notch, place
needle just Inferior to the superior orbital
rim, advance needle straight back ,inject
3ml of anesthetic.

32.  The risk of complications associated with
peribulbar block is low
 Peribulbar block has all the advantages of
retrobulbar block

33.  Peribulbar blocks have all the
disadvantages of retrobulbar blocks, but
less frequently
 The quality of akinesia and anesthesia may
not be as good as with retrobulbar block
 Often more than one injection is required

34.  The block takes much longer to work—it can
take up to 30 minutes
 The Honan balloon may be uncomfortable for
the patient
 Chemosis occurs in 80% of cases, which
makes operating conditions difficult
 In 5.8% of both retrobulbar and peribulbar
blocks, ptosis can remain for up to 90 days

35.  SubTenons block /pin point
anesthesia/medial episcleral block.
 Post limbal, subTenon’s incision (1 mm)
 Inferonasal quadrant - good fluid
distribution,avoids damage to vortex vein
 Short ciliary nerves are blocked

36.  The conjunctiva is anesthetized first with
drops of the local anesthetic of choice.
 The commonest approach is by the
infranasal quadrant
 The eye is cleaned and the patient asked to
look upwards and outwards.
 Aseptically, the conjunctiva andTenon’s
capsule are picked up 3–5 mm away from
the limbus using nontoothed forceps.
 A small incision is made through these
layers using scissors (Wescott scissors)
exposing the sclera.

37.  A sub-Tenon’s cannula is inserted
 The cannula is advanced posteriorly halfway
between the horizontal and vertical equators
of the globe.
 3 to 5milliliters of local anesthetic are injected;
the greater the volume, the greater the
akinesis.
 Lignocaine 2% is the gold standard(2.5ml);
bupivacaine 0.5% and articaine 2% .
 Hyaluronidase can be added.

38.  Less painful than peribulbar block
 Better analgesia than topical anesthesia
 Complications rarely serious
 No increase in intraocular pressure occurs with
the administration of local anesthetic
 Surgery can begin almost immediately Lasts for
60 minutes and supplemental anesthetic agent
can be given
 The globe can be voluntarily moved at the
surgeon’s instruction
 Low dose and low volume of anesthetic agent
are used

39.  The local anesthetic agent must be injected into
the capsule – double perforation of the capsule
results in anesthetic leaking out, which
decreases the effectiveness of the block
 Although it is an advantage that the globe can
be moved under instruction, it is important the
eye is not moved at other times – the use of
stabilizing sutures is advised
 Post-op morbidity: Chemosis and
subconjunctival haemorrhage.