Anatomy of the EyeAnatomy of the Eye

Anatomy of the EyeAnatomy of the Eye

Bones of the eyeBones of the eye

Eye Orbits: Eye Orbits: Are Pyramid Shaped Structures Are Pyramid Shaped Structures

Orbits Orbits

Each orbit contains the following Each orbit contains the following structures:structures:

GlobeGlobeOrbital FatOrbital FatExtraocular musclesExtraocular musclesPort of the lacrimal apparatus.Port of the lacrimal apparatus.NervesNervesBlood VesselsBlood Vessels

Orbits Orbits

The orbits of the eye extend from the base The orbits of the eye extend from the base at the front, & pointing posterior/medially at the front, & pointing posterior/medially toward the apex. toward the apex.

At the apex is located the optic foramen, At the apex is located the optic foramen, which transmits the optic nerve and its which transmits the optic nerve and its vessels. Also found in this area are the vessels. Also found in this area are the superior and inferior orbital fissures which superior and inferior orbital fissures which also transmits nerves & vesselsalso transmits nerves & vessels

Extraocular musclesExtraocular muscles

Extraocular MusclesExtraocular Muscles

Extraocular Muscles work with combined Extraocular Muscles work with combined action.action.

Consist of 4 rectus & 2 oblique muscles.Consist of 4 rectus & 2 oblique muscles.Allow for full ROM of the eye, includingAllow for full ROM of the eye, includingElevationElevationDepressionDepressionAbductionAbductionAdduction Adduction

Motor Nerve SupplyMotor Nerve Supply

Lateral Rectus Muscle supplied by: CN VI Lateral Rectus Muscle supplied by: CN VI (Aducents)(Aducents)

Superior Oblique supplied by: CN IV Superior Oblique supplied by: CN IV (Trochlear)(Trochlear)

Remainder supplied by: CN III Remainder supplied by: CN III (Occulomotor)(Occulomotor)

Sensory Nerve SupplySensory Nerve Supply

Sensory supply to the eye is provided by:Sensory supply to the eye is provided by:

CN V (trigeminal) its ophthalmic division. CN V (trigeminal) its ophthalmic division.

Vision is supplied by CN II (optic). Vision is supplied by CN II (optic).

Orbital FatOrbital Fat

Contains two compartments:Contains two compartments: Central compartment (retrobulbar & intracone)Central compartment (retrobulbar & intracone) Peripheral compartment (peribulbar & pericone)Peripheral compartment (peribulbar & pericone)

The importance of the orbital fat, is that it contains The importance of the orbital fat, is that it contains the motor & sensory nerves for the eye. the motor & sensory nerves for the eye.

Therefore regional anesthesia can be injected into Therefore regional anesthesia can be injected into the fat and provide the patient with an effective the fat and provide the patient with an effective block.block.

Orbital FatOrbital Fat

The GlobeThe Globe

The globe or eyeball itself is positioned at The globe or eyeball itself is positioned at the anterior part of the orbital cavity. It lies the anterior part of the orbital cavity. It lies closer to the roof of the orbit than the floor.closer to the roof of the orbit than the floor.

The sclera is the fibrous layer that The sclera is the fibrous layer that surrounds the globe except the cornea.surrounds the globe except the cornea.

The optic nerve penetrates the sclera The optic nerve penetrates the sclera posteriorly & 1-2 mm medially.posteriorly & 1-2 mm medially.

The central retinal artery & vein follow the The central retinal artery & vein follow the optic nerve pathway.optic nerve pathway.

Axial LengthAxial Length

Corneal surface to the retina:Corneal surface to the retina:

Normal 25 mm (range 12-35)Normal 25 mm (range 12-35)

Large eye: >26mmLarge eye: >26mm

Is many times measured preop. Is many times measured preop.

Larger globes carry increased risk ofLarger globes carry increased risk of

perforation when regional anesthetics areperforation when regional anesthetics are

performed.performed.

Anatomical Facts related to eyesAnatomical Facts related to eyes

optic nerve lies on medial side of midsagittal plane optic nerve lies on medial side of midsagittal plane of eyeof eye

Optic nerve and extraocular muscle origins are Optic nerve and extraocular muscle origins are tightly packed at the apex of the orbittightly packed at the apex of the orbit

Arterial blood supply to orbit and contents= Arterial blood supply to orbit and contents= ophthalmic artery (branch of internal carotid artery)ophthalmic artery (branch of internal carotid artery)

The principal vein= superior ophthalmicThe principal vein= superior ophthalmic Ciliary ganglion lies in posterior part of orbit, Ciliary ganglion lies in posterior part of orbit,

receiving preganglionic fibers through the receiving preganglionic fibers through the oculomotor nerve oculomotor nerve

Edinger-Westphal nucleus- when excited, it leads to Edinger-Westphal nucleus- when excited, it leads to miosis—opiods excite this and atropine blocks miosis—opiods excite this and atropine blocks effects leading to mydriasiseffects leading to mydriasis

Ophthalmic nerve-Ophthalmic nerve- sensory, supplying lacrimal sensory, supplying lacrimal gland, conjunctiva, skin and gland, conjunctiva, skin and mucous membrane of nose, mucous membrane of nose, skin of foreheadskin of forehead

3 branches: lacrimal, frontal, 3 branches: lacrimal, frontal, nasociliarynasociliary

Motor nerves to Motor nerves to extraocular muscles: extraocular muscles:

1.1.OculomotorOculomotor (3)- (3)- supplies iris (raises supplies iris (raises upper eyelids) and all upper eyelids) and all ocular muscles except ocular muscles except lateral rectus lateral rectus

2. 2. Inferior rectus-Inferior rectus- rotates eye downrotates eye down

3. 3. Inferior oblique-Inferior oblique- rotates eye up and outrotates eye up and out

Facial Nerve- (7)Facial Nerve- (7)motor nerve- supplies motor nerve- supplies orbicularis oculi muscle, orbicularis oculi muscle, responsible for blinking and responsible for blinking and lid squeezing.lid squeezing.

(can block this nerve at (can block this nerve at mastoid area but more mastoid area but more complications with this so complications with this so not commonly done)not commonly done)

ADVANTAGES OF LOCAL ADVANTAGES OF LOCAL ANAESTHESIAANAESTHESIA

1.SAFETY:1.SAFETY:Many eye patients are elderly and may have Many eye patients are elderly and may have

chronic respiratory or cardio-vascular chronic respiratory or cardio-vascular disease.They may deteriorate with GA disease.They may deteriorate with GA .After GA there is always .After GA there is always risk of post-operative confusion especially in the risk of post-operative confusion especially in the elderly, and coughing andelderly, and coughing and

vomiting may cause complications after an vomiting may cause complications after an intraocular operation. intraocular operation.

After GA there is also a slight risk of post-After GA there is also a slight risk of post-operative chest infection or deep vein thrombosisoperative chest infection or deep vein thrombosis

1919

2.SPEED OF RECOVERY:2.SPEED OF RECOVERY:

LA is quicker than GA because less time is LA is quicker than GA because less time is required to give the anaesthetic. In particular a required to give the anaesthetic. In particular a patient after LA can go straight out of the patient after LA can go straight out of the operating room, but after GA the patient must be operating room, but after GA the patient must be carefully nursed by skilled staff until full carefully nursed by skilled staff until full consciousness has returned.consciousness has returned.

3. COST:3. COST: The cost of the equipment and anaesthetic The cost of the equipment and anaesthetic

agents is obviously much less with LA.agents is obviously much less with LA.

2.SPEED OF RECOVERY:2.SPEED OF RECOVERY:

LA is quicker than GA because less time is LA is quicker than GA because less time is required to give the anaesthetic. In particular a required to give the anaesthetic. In particular a patient after LA can go straight out of the patient after LA can go straight out of the operating room, but after GA the patient must be operating room, but after GA the patient must be carefully nursed by skilled staff until full carefully nursed by skilled staff until full consciousness has returned.consciousness has returned.

3. COST:3. COST: The cost of the equipment and anaesthetic The cost of the equipment and anaesthetic

agents is obviously much less with LA.agents is obviously much less with LA.

INDICATIONS FOR GA IN EYE INDICATIONS FOR GA IN EYE SURGERIES:SURGERIES:

• • Children. Children. Young children must be given a GA, and in Young children must be given a GA, and in

older children GA is older children GA is preferable for all except very preferable for all except very minor proceduresminor procedures..

• • Penetrating eye injuriesPenetrating eye injuries. .

LA is difficult to give effectively. There is often LA is difficult to give effectively. There is often orbital orbital haemorrhage, and there is a risk of raising haemorrhage, and there is a risk of raising the pressure in the eye and expelling some of the pressure in the eye and expelling some of the ocular contents after LA.the ocular contents after LA.

Major surgery or long operations such Major surgery or long operations such as exenteration or retinal detachment as exenteration or retinal detachment surgerysurgery..

• • Confused or demented patients are Confused or demented patients are better operated upon under GA.better operated upon under GA.

Nerve blocks:Nerve blocks:

With this technique the anaesthetic agent is With this technique the anaesthetic agent is injected close to the main trunk of a nerve or its injected close to the main trunk of a nerve or its branches so that its sensory or motor function is branches so that its sensory or motor function is blocked. This is the usual way of giving LA for blocked. This is the usual way of giving LA for intraocular surgery. With a nerve block a intraocular surgery. With a nerve block a relatively small injection can achieve a large relatively small injection can achieve a large effect. However a stronger solution of effect. However a stronger solution of anaesthetic may be necessary and lignocaine anaesthetic may be necessary and lignocaine 2% is the usual agent. 2% is the usual agent.

Preoperative Assessment of the Patient’s Preoperative Assessment of the Patient’s General Health:General Health:

It may not be possible to carry out a full medical It may not be possible to carry out a full medical examination, but the patient’s heart and lungs examination, but the patient’s heart and lungs should be examined to make sure there are no should be examined to make sure there are no signs of heart failure, breathing difficulties, or signs of heart failure, breathing difficulties, or uncontrolled coughing.The blood pressure uncontrolled coughing.The blood pressure should be measured to check for should be measured to check for hypertension, hypertension, and the urine tested for sugar to exclude and the urine tested for sugar to exclude diabetes.diabetes.

Sedation:Sedation: Any patient having intraocular surgery under local Any patient having intraocular surgery under local

anaesthetic will be frightened and anxious. anaesthetic will be frightened and anxious. Reassurance and explanation is much more valuable Reassurance and explanation is much more valuable than any amount of tablets or injections. Usually the than any amount of tablets or injections. Usually the patient will not need any further patient will not need any further sedation and will relax sedation and will relax and lie still for the operation. and lie still for the operation.

Diazepam (Valium) is most commonly used, the oral Diazepam (Valium) is most commonly used, the oral dose being 5 mg for a frail person and 10 mg for a robust dose being 5 mg for a frail person and 10 mg for a robust person one or two hours before the operation.person one or two hours before the operation.

AIMS OF LA:AIMS OF LA: 1. Anaesthesia of the eye:1. Anaesthesia of the eye: The sensory fibres from the eye pass in the The sensory fibres from the eye pass in the

ophthalmic branch of the trigeminal nerve (the ophthalmic branch of the trigeminal nerve (the 5th. cranial nerve).The cornea, iris and sclera 5th. cranial nerve).The cornea, iris and sclera are extremely sensitive to pain, while the are extremely sensitive to pain, while the conjunctiva is less sensitive.conjunctiva is less sensitive.

2. Paralysis of the extraocular muscles 2. Paralysis of the extraocular muscles A moving eye makes surgery very difficult. In A moving eye makes surgery very difficult. In

addition the pull of the muscles on the sclera addition the pull of the muscles on the sclera once the eye has been opened will increase the once the eye has been opened will increase the intraocular pressure and make prolapse of the intraocular pressure and make prolapse of the contents much more likely.contents much more likely.

3. Paralysis of the orbicularis oculi 3. Paralysis of the orbicularis oculi muscle which closes the eyelids.muscle which closes the eyelids.

This muscle is supplied by the facial nerve (the This muscle is supplied by the facial nerve (the 7th cranial nerve). If the patient is squeezing his 7th cranial nerve). If the patient is squeezing his eye shut during the operation surgical exposure eye shut during the operation surgical exposure will be difficult.will be difficult.

There is also a serious risk that once the eye There is also a serious risk that once the eye has been opened the pressure of thehas been opened the pressure of the eyelids eyelids may force the ocular contents out.may force the ocular contents out.

To block the vision by anaesthetising To block the vision by anaesthetising the optic nerve (2nd cranial nerve).the optic nerve (2nd cranial nerve).

In this way the patient is not upset by the bright In this way the patient is not upset by the bright operating theatre lightoperating theatre light..

These four aims may be achieved by two These four aims may be achieved by two nerve blocks, the nerve blocks, the facial and retrobulbar facial and retrobulbar block, or alternatively two separate block, or alternatively two separate injections into the orbit called the injections into the orbit called the peribulbar peribulbar block may be given. Recently block may be given. Recently a a sub-Tenon’s block using a blunt sub-Tenon’s block using a blunt cannula has been cannula has been described.described.

AGENTS USED IN NERVE AGENTS USED IN NERVE BLOCKS:BLOCKS: Lignocaine 2% is the most popular agent for nerve Lignocaine 2% is the most popular agent for nerve

blocks. It has a rapid onsetblocks. It has a rapid onsetof action and will usually last for of action and will usually last for an hour.an hour.

An alternative is An alternative is Bupivacaine (Marcain)Bupivacaine (Marcain)0.5% or 0.75%. It is 0.5% or 0.75%. It is more expensive, its onset of action is not so rapid but it lasts more expensive, its onset of action is not so rapid but it lasts for up to 3 hours or longer. Some surgeons use a 50/50 for up to 3 hours or longer. Some surgeons use a 50/50 mixture of Lignocaine and Bupivacaine to try to get the mixture of Lignocaine and Bupivacaine to try to get the advantages of each.advantages of each.

Adrenaline (Epinephrine) 1:100,000 should always be Adrenaline (Epinephrine) 1:100,000 should always be added to the facial added to the facial block and most people add it to the block and most people add it to the peribulbar block. Its addition slows the absorption time so that peribulbar block. Its addition slows the absorption time so that the anaesthetic lasts longer and the risks of the systemic toxic the anaesthetic lasts longer and the risks of the systemic toxic side-effects from rapid absorption of local anaesthetic are side-effects from rapid absorption of local anaesthetic are less.Adrenaline is usually not used in retrobulbar injection, less.Adrenaline is usually not used in retrobulbar injection, because of possible risk of causing vasoconstriction in the because of possible risk of causing vasoconstriction in the retinal or choroidal arteries. retinal or choroidal arteries.

Hyaluronidase (Hyalase) in a strength of Hyaluronidase (Hyalase) in a strength of approximately 25 to 50 units/ml may approximately 25 to 50 units/ml may be added to be added to the retrobulbar or peribulbar injections only. (One the retrobulbar or peribulbar injections only. (One ampoule of hyalase containing 1500 units is usually ampoule of hyalase containing 1500 units is usually added to a 20 ml or 50 ml bottle of 2% lignocaine.added to a 20 ml or 50 ml bottle of 2% lignocaine.

The hyaluronidase helps the local anaesthetic to The hyaluronidase helps the local anaesthetic to spread through the tissues, and so increases the spread through the tissues, and so increases the effectiveness of the nerve block, especially with a effectiveness of the nerve block, especially with a retrobulbar injection where so many nerves need to retrobulbar injection where so many nerves need to be blocked by a single injection. Adding be blocked by a single injection. Adding hyaluronidase means that a smaller amount of hyaluronidase means that a smaller amount of injection has a better effect. injection has a better effect.

NERVE BLOCKSNERVE BLOCKS

Retrobulbar Block (intracone)Retrobulbar Block (intracone)Peribulbar Block (extracone)Peribulbar Block (extracone)Sub-Tenon BlockSub-Tenon BlockFacial Nerve BlockFacial Nerve Block

The Facial BlockThe Facial Block

If the surgeon plans to give a retrobulbar and a facial If the surgeon plans to give a retrobulbar and a facial block, it is usual to give the facial block first and block, it is usual to give the facial block first and the retrobulbar block second.The facial block can the retrobulbar block second.The facial block can be given at the neck of the mandible (the O’Brien be given at the neck of the mandible (the O’Brien method), or at the orbital rim (theVan Lint method). method), or at the orbital rim (theVan Lint method). In each case 5 ml of 2% lignocaine with adrenaline In each case 5 ml of 2% lignocaine with adrenaline are used with a 21G needle.are used with a 21G needle.

The O’Brien Method (figs. 4.1 and 4.2):The O’Brien Method (figs. 4.1 and 4.2): Principle:Principle: The divisions of the facial nerve are blocked as The divisions of the facial nerve are blocked as

they pass around the neck of the mandible.they pass around the neck of the mandible.

Method:Method: 1. The temporo-mandibular joint and the neck of the mandible are 1. The temporo-mandibular joint and the neck of the mandible are

palpated while the patient opens and closes his mouth.palpated while the patient opens and closes his mouth. 2. The needle is inserted perpendicularly through the skin and is 2. The needle is inserted perpendicularly through the skin and is

pushed down to the neck of the mandible.The tip should touch the pushed down to the neck of the mandible.The tip should touch the bone.This corresponds to a point about 1 cm anterior and 1 cm bone.This corresponds to a point about 1 cm anterior and 1 cm below the external meatus of the ear.below the external meatus of the ear.

3. After withdrawing slightly on the plunger to ensure that the needle 3. After withdrawing slightly on the plunger to ensure that the needle is not in a blood vessel, up to 5 ml of anaesthetic is slowly injected is not in a blood vessel, up to 5 ml of anaesthetic is slowly injected as close as possible to the bone.as close as possible to the bone.

4. The syringe is removed and the site massaged vigorously.4. The syringe is removed and the site massaged vigorously.

TheVan Lint Method (figs. 4.1 and 4.2):TheVan Lint Method (figs. 4.1 and 4.2): Principle:Principle:

Paralysis of the orbicularis oculi muscle by local Paralysis of the orbicularis oculi muscle by local infiltration around the orbit.infiltration around the orbit.

Method:Method:

1. The needle is inserted through the skin at the 1. The needle is inserted through the skin at the lateral margin of the orbit and pushed down to the lateral margin of the orbit and pushed down to the bone.There is very little subcutaneous tissue bone.There is very little subcutaneous tissue here.Try toavoid blunting the tip of the needle on the here.Try toavoid blunting the tip of the needle on the bone. A bleb is raised using about 1 ml of lignocainebone. A bleb is raised using about 1 ml of lignocaine

2. The needle is then advanced to its full extent 2. The needle is then advanced to its full extent in three directions. Firstly along the upper in three directions. Firstly along the upper orbital margin, then along the lower orbital orbital margin, then along the lower orbital margin and finally along the zygomatic arch margin and finally along the zygomatic arch back towards the ear.The needle must be kept back towards the ear.The needle must be kept close to the bone so as to be under the close to the bone so as to be under the orbicularis muscle.This is because the motor orbicularis muscle.This is because the motor nerves enter the muscle on its deep side. The nerves enter the muscle on its deep side. The lignocaine is injected as the needle is lignocaine is injected as the needle is advanced. A total of 4 ml is distributed equally advanced. A total of 4 ml is distributed equally in the 3 directions.in the 3 directions.

3. On removal of the needle the area is 3. On removal of the needle the area is massaged.massaged.

Complications of facial nerve Complications of facial nerve block:block:

1.Failure of the block1.Failure of the block 2.Tenderness over the temporo-mandibular 2.Tenderness over the temporo-mandibular

joint.joint. 3. Permanent weakness of the facial nerve.3. Permanent weakness of the facial nerve. 4. Injection into the branches of the external 4. Injection into the branches of the external

carotid artery or jugular veincarotid artery or jugular vein..

The Retrobulbar Block (figs. The Retrobulbar Block (figs. 4.3 and 4.4)4.3 and 4.4)

Principle:Principle: The retrobulbar space lies inside the extraocular The retrobulbar space lies inside the extraocular

muscle cone behind the eye.The 2nd, 3rd, 6th and muscle cone behind the eye.The 2nd, 3rd, 6th and branches of the 5th cranial nerves are all found in branches of the 5th cranial nerves are all found in this space and the 4th nerve passes very near. this space and the 4th nerve passes very near. Therefore all the nerves supplying the eye and Therefore all the nerves supplying the eye and extraocular muscles are blocked by one injection of extraocular muscles are blocked by one injection of local anaesthetic into the retrobulbar space. After a local anaesthetic into the retrobulbar space. After a successful block there is no sensation, no movement successful block there is no sensation, no movement and no vision in the eye.and no vision in the eye.

Indications:Indications:

• • Intraocular surgeryIntraocular surgery

• • Evisceration or enucleationEvisceration or enucleation

• • As a supplement to ketamine general As a supplement to ketamine general anaesthesiaanaesthesia

OUCH!!!!

TECHNIQUESTECHNIQUES(transconjunctival or transcutaneous)(transconjunctival or transcutaneous)

Local anesthetic is injected Local anesthetic is injected behind the eye into the cone behind the eye into the cone formed by extraocular muscles formed by extraocular muscles (see picture)(see picture)

Patient supine or sitting, Patient supine or sitting, looking straight ahead (primary looking straight ahead (primary gaze) gaze)

Use fine needle or blunt 23-27 Use fine needle or blunt 23-27 gauge needlegauge needle

Penetrates lower lid at the Penetrates lower lid at the junction of the middle and junction of the middle and lateral one-third of the orbit lateral one-third of the orbit

After aspiration, to ensure not After aspiration, to ensure not intravascular, 2-5ml of local is intravascular, 2-5ml of local is injected and removedinjected and removed

CHOICE OF LOCAL:CHOICE OF LOCAL: Lidocaine-2%Lidocaine-2% Bupivacaine-0.5%Bupivacaine-0.5% RopivacaineRopivacaine Addition of epi (1:200,000 or Addition of epi (1:200,000 or

300,000) may reduce bleeding 300,000) may reduce bleeding and prolongs blockand prolongs block

Do not use epi if patient has Do not use epi if patient has decreased blood supply to eyedecreased blood supply to eye

Can use just lidocaine if quick Can use just lidocaine if quick surgery but bupivacaine is surgery but bupivacaine is better with epi if longer surgerybetter with epi if longer surgery

Techniques Continued….Techniques Continued…. So.. Place needle with local attached at the inferolateral border So.. Place needle with local attached at the inferolateral border

of bony orbit and direct it toward the apex of orbit, follow at 10 of bony orbit and direct it toward the apex of orbit, follow at 10 degree upward angle.degree upward angle.

A A poppop is felt as needle tip enters orbital muscle cone is felt as needle tip enters orbital muscle cone Aspirate and inject 3-5cc of local Aspirate and inject 3-5cc of local Do not introduce needle too posteriorDo not introduce needle too posterior A successful block is accompanied by anesthesia, akinesia, A successful block is accompanied by anesthesia, akinesia,

and abolishment of oculocephalic reflex (a blocked eye does and abolishment of oculocephalic reflex (a blocked eye does not move during head turning) IMPORTANT!not move during head turning) IMPORTANT!

Surgeon can use hyaluronidase (hydrolyzer of connective Surgeon can use hyaluronidase (hydrolyzer of connective tissue polysaccharides) to enhance block and spread of local tissue polysaccharides) to enhance block and spread of local anesthetic. This allows block of facial nerve which innervates anesthetic. This allows block of facial nerve which innervates orbicularis oculi muscleorbicularis oculi muscle

Complications of Retrobulbar Complications of Retrobulbar AnaesthesiaAnaesthesia

11. Inadequate anaesthesia and akinesia.. Inadequate anaesthesia and akinesia.

2. Retrobulbar haemorrhage.2. Retrobulbar haemorrhage.

3. Injection into a blood vessel or into the 3. Injection into a blood vessel or into the cerebrospinal fluid.cerebrospinal fluid.

4. Injection into the eyeball.4. Injection into the eyeball.

5. Permanent neurological damage.5. Permanent neurological damage.

6. Toxic reaction from excessive anaesthetic6. Toxic reaction from excessive anaesthetic ..

1. Inadequate anaesthesia and akinesia1. Inadequate anaesthesia and akinesia The best test of success of a retrobulbar block is The best test of success of a retrobulbar block is

to examine the ocular movements.If these have to examine the ocular movements.If these have been blocked, there will almost always be been blocked, there will almost always be adequate anaesthesia. If there is almost a full adequate anaesthesia. If there is almost a full range of eye movements then the block may be range of eye movements then the block may be repeated once.repeated once.

Sometimes the block fails because of poor Sometimes the block fails because of poor technique. Either the needle is passed along the technique. Either the needle is passed along the orbital floor and not into the muscle cone or orbital floor and not into the muscle cone or alternatively the needle is not advanced far alternatively the needle is not advanced far enough out of fear of penetrating the eyeball.enough out of fear of penetrating the eyeball.

Despite an otherwise adequate block the Despite an otherwise adequate block the eye may rotate upwards due to the eye may rotate upwards due to the continued action of the superior rectus. In continued action of the superior rectus. In these cases the superior rectus may these cases the superior rectus may require further anaesthesia. 1 ml of 2% require further anaesthesia. 1 ml of 2% lignocaine is injected above the eye either lignocaine is injected above the eye either through the conjunctiva or through the through the conjunctiva or through the upper eye lid.upper eye lid.

2. Retrobulbar Haemorrhage: 2. Retrobulbar Haemorrhage: Slight retrobulbar Slight retrobulbar haemorrhage is quite common and is caused by a haemorrhage is quite common and is caused by a small blood vessel being pierced by the retrobulbar small blood vessel being pierced by the retrobulbar needle. Often it is only noted postoperatively,when needle. Often it is only noted postoperatively,when there may be bruising of the eyelids or a there may be bruising of the eyelids or a subconjunctival haemorrhage as the blood tracks subconjunctival haemorrhage as the blood tracks forward. Severe retrobulbar haemorrhage causing forward. Severe retrobulbar haemorrhage causing proptosis should occur in less than 1% of cases. If proptosis should occur in less than 1% of cases. If there is proptosis the operation must be postponed there is proptosis the operation must be postponed as the raised orbital pressure will increase the risk of as the raised orbital pressure will increase the risk of serious complications during surgery.A firmpad and serious complications during surgery.A firmpad and bandage should be applied and the operation can be bandage should be applied and the operation can be repeated when the haemorrhage has completely repeated when the haemorrhage has completely subsided.there is possible risk of optic nerve subsided.there is possible risk of optic nerve compression & optic atrophy.compression & optic atrophy.

• •. Damaged orhooked tips can tear . Damaged orhooked tips can tear delicate blood vessels.Excessive delicate blood vessels.Excessive movement of the needle increases movement of the needle increases the risk of haemorrhage.the risk of haemorrhage.

• • Applying Applying gentle pressure on the eye gentle pressure on the eye immediately after withdrawing the immediately after withdrawing the needle will needle will limit any blood leaking limit any blood leaking from small vessels.from small vessels.

3. Injection into a blood vessel or into the 3. Injection into a blood vessel or into the cerebrospinal fluid.cerebrospinal fluid.

Injection into a blood vessel is best avoided by Injection into a blood vessel is best avoided by slightly withdrawing the plunger ofthe syringe before slightly withdrawing the plunger ofthe syringe before injecting. Injection into a vein can cause cardiac injecting. Injection into a vein can cause cardiac irregularities,collapse or convulsions. irregularities,collapse or convulsions. Injections into a retinal or ciliary artery can Injections into a retinal or ciliary artery can caustemporary or permanent visual defects.caustemporary or permanent visual defects.

The optic nerve is surrounded by dura mater The optic nerve is surrounded by dura mater containing cerebro-spinal fluidand it is possible to put containing cerebro-spinal fluidand it is possible to put the needle through the dural sheath and thus inject the needle through the dural sheath and thus inject lignocaine into the cerebrospinal fluid. This can cause lignocaine into the cerebrospinal fluid. This can cause loss of consciousness,respiratory arrest and loss of consciousness,respiratory arrest and convulsions.convulsions.

•

The risk of injecting into cerebrospinal fluid is reduced The risk of injecting into cerebrospinal fluid is reduced by taking 2 precautions. by taking 2 precautions. Firstly, by not advancing Firstly, by not advancing the retrobulbarneedle more than 30–35 mm from the the retrobulbarneedle more than 30–35 mm from the skin. skin. Secondly when giving the Secondly when giving the retrobulbarinjection, making sure the patient is looking retrobulbarinjection, making sure the patient is looking straight forward and not look up if the patient looks up straight forward and not look up if the patient looks up this brings down the back of the eyeball and the optic this brings down the back of the eyeball and the optic nerveand thus nearer to the path of the retrobulbar nerveand thus nearer to the path of the retrobulbar needle.needle.

If the patient’s airway is protected and artificial ventilation If the patient’s airway is protected and artificial ventilation and cardiac resuscitation given, the patient should and cardiac resuscitation given, the patient should usually recover completely from unconsciousnessor usually recover completely from unconsciousnessor collapse caused by intravenous or cerebrospinal injection collapse caused by intravenous or cerebrospinal injection of local anaesthetic.of local anaesthetic.

4. Injection into or through the eyeball.4. Injection into or through the eyeball. This usually occurs because the needle is directed This usually occurs because the needle is directed

and advanced incorrectly. and advanced incorrectly.

.The risk is increased in myopic eyes which are .The risk is increased in myopic eyes which are large and have thin sclera. If the injection is into large and have thin sclera. If the injection is into the eye it will become very hard on injection and the eye it will become very hard on injection and the cornea may become opaque This usually the cornea may become opaque This usually results in blindness. results in blindness. .If the injection .If the injection is through the eye it may become very softis through the eye it may become very soft

This is best avoided by advancing the This is best avoided by advancing the needle slowly and not pushing against any needle slowly and not pushing against any resistance once the tip of the needle has resistance once the tip of the needle has passed through the orbital septum. If the passed through the orbital septum. If the needle does meet resistance, in most needle does meet resistance, in most cases it will be the bone on thefloor of the cases it will be the bone on thefloor of the orbit. It should be withdrawn just a fraction orbit. It should be withdrawn just a fraction and then redirected moreupwards. If and then redirected moreupwards. If resistance is still felt it is probably hitting resistance is still felt it is probably hitting the eyeball, and not the floorof the orbit. In the eyeball, and not the floorof the orbit. In this case it should be very carefully and this case it should be very carefully and gently redirected a littlemore downwards.gently redirected a littlemore downwards.

5. Long-term neurological damage5. Long-term neurological damage Permanent damage to one of the cranial nerves in the Permanent damage to one of the cranial nerves in the

orbit may very rarely occur.orbit may very rarely occur. 6. Toxic reaction from excessive anaesthetic6. Toxic reaction from excessive anaesthetic The amounts of local anaesthetic that are given for a The amounts of local anaesthetic that are given for a

facial and retrobulbar block,and for a peribulbar block facial and retrobulbar block,and for a peribulbar block are quite close to the recommended maximum dose for are quite close to the recommended maximum dose for safety.This is especially true if hyalase is added safety.This is especially true if hyalase is added because it increases the absorption rate of the because it increases the absorption rate of the anaesthetic. By contrast, adding adrenaline slows down anaesthetic. By contrast, adding adrenaline slows down the absorption rate.The signs of local anaesthetic the absorption rate.The signs of local anaesthetic toxicity are similar to those from injecting into the blood toxicity are similar to those from injecting into the blood stream:-cardiac irregularities and collapse.stream:-cardiac irregularities and collapse.

The Peribulbar blockThe Peribulbar block Principle:Principle: Two fairly large volumes of local anaesthetic are Two fairly large volumes of local anaesthetic are

given around the eye outside thegiven around the eye outside the extraocular muscle cone. These spread slowly extraocular muscle cone. These spread slowly

into the retrobulbar space as wellinto the retrobulbar space as well producing anaesthesia and akinesia of the eye producing anaesthesia and akinesia of the eye

and eyelids.and eyelids.

PERIBULBAR BLOCKPERIBULBAR BLOCK

In contrast to retrobulbar block, this block does not In contrast to retrobulbar block, this block does not penetrate the cone formed by the extraocular penetrate the cone formed by the extraocular muscles. Both techniques achieve akinesia of the muscles. Both techniques achieve akinesia of the eye equally well. eye equally well.

Advantages over retro block are: less risk of eye Advantages over retro block are: less risk of eye pentration, optic nerve and artery, and less pain on pentration, optic nerve and artery, and less pain on injection.injection.

Disadvantages include: slower onset and increased Disadvantages include: slower onset and increased likelihood of ecchymosis ( bruising) likelihood of ecchymosis ( bruising)

TECHNIQUETECHNIQUE Larger volume of Local Larger volume of Local

neededneeded Patient is supine and looking Patient is supine and looking

straight aheadstraight ahead Topical can be used first in Topical can be used first in

the conjunctiva (check for the conjunctiva (check for allergies) topical can cause allergies) topical can cause phacoemulsifications (lens phacoemulsifications (lens disindegration)disindegration)

As eyelid is retracted, As eyelid is retracted, inferotemporal injection is inferotemporal injection is given halfway between given halfway between lateral canthus and lateral lateral canthus and lateral limbus.limbus.

Needle is advanced under Needle is advanced under globe parallel to the orbital globe parallel to the orbital floor and when it passes the floor and when it passes the equator of the eye it is equator of the eye it is directed slightly medial (20’) directed slightly medial (20’) and cephalad (10’).and cephalad (10’).

Differences in Retro and Peri Differences in Retro and Peri BlocksBlocks

SubTenon’s BlockSubTenon’s BlockPrinciple:Principle:To avoid the risks from using sharp To avoid the risks from using sharp

needles, a blunt cannula is advanced into needles, a blunt cannula is advanced into thethe

retrobulbar space to deliver the retrobulbar space to deliver the anaesthetic.anaesthetic.

Sub-Tenon BlockSub-Tenon Block Tenon’s Fascia surrounds the globe and the Tenon’s Fascia surrounds the globe and the

extraocular muscles.extraocular muscles. Local anesthetic injected beneath it diffuses into the Local anesthetic injected beneath it diffuses into the

retrobulbar space. retrobulbar space. Blunt 25 or 19 gauge curved needle usedBlunt 25 or 19 gauge curved needle used After topical anesthesia, the conjunctiva is lifted After topical anesthesia, the conjunctiva is lifted

along with the fascia with forcepsalong with the fascia with forceps A small nick is made with scissors and the needle is A small nick is made with scissors and the needle is

passed under the tenon’s fascia. passed under the tenon’s fascia. This block is commonly used for cataract surgeryThis block is commonly used for cataract surgery

MANDIBULAR NERVEMANDIBULAR NERVE

Anterior buccal nerve ,motor nerve Anterior buccal nerve ,motor nerve posterior auriculotemporal ,inferior posterior auriculotemporal ,inferior alveolar,lingual , BRANCHESalveolar,lingual , BRANCHES