Ophthalmic anesthesia Dr. S. Parthasarathy MD., DA., DNB, MD (Acu), Dip. Diab. DCA, Dip. Software statistics- PhD ( physiology), IDRA

History The “Year 1884” Carl Koller discovered cocaine hydrochloride as a topical anaesthetic agent for performing eye surgery Herman Knapp used cocaine for retrobulbar injection and performed enucleation

Relevant anatomy Pyramid towards middle cranial fossa Medial walls enclose nasal cavity Lateral walls make an axis different from globe 4 – 5.5 cm

The globe occupies the anterior part of the Orbit axial length of 20–25 mm elongated in myopic individuals Rectus muscle along with fibro tendinous sheath form a cone SO4 , LR6. others 3 ( nerves) Levator palpabrae – 3 Orbicularis oculi – facial nerve Tenon’s capsule is a thin membrane, which covers the globe.

The sensory supply of the globe is via the long and short ciliary nerves, which are branches of the nasociliary nerve, itself a branch of the ophthalmic division of the trigeminal nerve. Optic nerve – deep medial injection

Injections of fluid within the orbit will inevitably give rise to pressure on the globe and an increase in intraocular pressure Mild proptosis Not more than 30 mmHg pressure Preblock scan of the globe

IV midazolam or / fentanyl Three types of block Retrobulbar block Peribulbar block Subtenon’s block Preop assessment IV midazolam or / fentanyl

Indications Cataract surgery, vitreoretinal surgery, panretinal photocoagulation, trabeculectomy, optic nerve sheath fenestration, delivery of drugs (steroids, neurolytic agents), strabismus surgery in willing patients. delivery of neurolytic agents for the treatment of chronic orbital pain.

Retrobulbar block Topical anesthesia of cornea (clouding ?) Inferotemporal quadrant injection Patient to view straight Scleral or from the skin Previous – superomedial gaze (atkinson)– optic nerve damage Now modified straight gaze 10 – 15 mm , change go in , 4 – 5 ml The best position for the patient is a semi-recumbent position (45°).

Technique

Skin or sclera

Drugs 2 % lignocaine or 0.5 % bupi or 0.75 % ropi 1 in 2 lakh adrenaline + 150 IU hyaluronidase Akinesia is good , small volume , quick onset 26 G - one and half inch needle

Pressure Manual Thirty seconds-- Five second gap The ocular compression device most commonly used is Honan’s balloon which is applied for 10-20 min with the pressure set at 30 mmHg If akinesia is incomplete , median peribulbar block supplementation

Complications Hemorrhage in the very well-vascularized orbit, with a frequency of 0.7–1.7 % (known as “compartment syndrome”), can lead to blindness. Chemosis Perforation – esp. myopic patients Injury to optic nerve Subarachnoid Intravascular OCR Myositis

Retro bulbar haemorhage Steroids NSAIDS, aspirin, anticoagiulants Proptosis, SCH , chemosis etc If CRA pressure decreases , urgent decompression Postpone surgery But very mild no further bleeding outside, Proceed with surgery 45 minutes later

Penetration ( one side ) Perforation( through & thro) Both retrobulbar and peribulbar Pain and loss of vision prevention is the best

Myopathies Muscle weakness Corneal abrasion ( pressure)

Peribulbar block Inferotemporal Medial canthal Caruncular( Supplement) Volume is slightly higher Complications are less Akinesia is more complete Facial nerve block – not necessary

Pictures from the internet for closed academic circles only 25-G, 31-mm-long needle is inserted through the conjunctivaas far laterally as possible in the infero temporal quadrant. Once the needle is under the globe, it is not directed upward and inward, but it is directed along the orbital floor. Five ml of LA Medial canthal or caruncular as supplements – peribulbar blocks

So called safety of outside the cone Volume higher Akinesia OK Can be late Direct injury rates less ?? Why these sites No direct injection into the muscle

Sub tenon’s block Tenon’s capsule is a dense, fibrous layer of elastic tissue surrounding the eye and extra ocular muscles in the orbit Potential space between posterior sclera and tenon’s capsule Deposit LA

LA here --along the extraocular muscle sheaths, diffusion into the retrobulbar space, spread into the fascial planes around the lids, as well as a direct action on the nerves supplying the globe that pass through this space.

LA topical Lid retraction Infero medial - Spring scissors – sclera incised Cannula inserted to posterior part of the globe 4- 5 ml

Pictures from the internet for closed academic circles only Infero medial Cannula insertion

Subtenon’s block Little resistance usually More resistance – some problem somewhere Position better Big conjunctival swelling – compress and take out Mild protrusion is acceptable 7 – 10 mm from limbus is success Excellent rapid analgesia Post operative analgesia

Less volume – near by muscles are affected but distant LR may be spared Advantageous in squint surgery Scleral cautery is possible Anticoagulants – OK Chemosis and conjunctival haemorhage should be explained No sharp needles !!

Facial nerve for orbicularis oculi Atkinson

What is needed ? Cornea and conjunctiva – topical or blocks Extraocular muscles – blocks ( peri or retobulbar ) Orbicularis oculi – facial nerve

You can”t do this after complete anesthesia Check patient is correct Check side is correct

Summary Thank you all Relevant anatomy Indications Three types of block Advantages and disadvantages Facial nerve block Thank you all