Eyes

Front 1

Basic anatomy

Back 1

- orbit is pyramidal in shape with base at orbital opening and apex pointing toward optic foramen
- globe lies in anterior part of orbit and sits high and lateral
- sensory innervation from long and short ciliary nerves (branches of trigeminal nerve, predominantly V1 but also V2)

Front 2

optic foramen

Back 2

- transmits optic nerve and ophthalmic artery

Front 3

superior orbital fissure

Back 3

- transmits 3, 4, V1, V2 and superior and onferior ophthalmic veins

Front 4

how to perform subtenons

Back 4

- consent, time out, suitable location, trained assistant, resus equipment, IV access, monitoring...
- have patient look up and out to expose inferonasal quadrant
- topical anaesthesia with amethocaine/oxybuprocaine
- inferonasal quadrant, pick up conjunctiva with moorfield forceps and cut with westcott scissors 7mm from limbus.
- blunt dissect with westcott scissors to equator
- insert tenons cannula, inject 6 mls of LA
- ensure no ballooning of conjunctiva as indicates incorrect plane

Front 5

Anatomy relevant to sub-tenons

Back 5

- tenon's capsule lies below the conjunctiva and above the sclera
- potential space
- anteriorly joins with the conjunctiva and posterior with the dura of the optic nerve
- divided into anterior and posterior parts. with age posterior part thins aiding diffusion of LA into retrobulbar cone

Front 6

How subtenons causes akinesia

Back 6

-LA spreads from posterior section of subtenons space into retrobulbar cone
- supplements the direct effects on the sensory nerves

Front 7

Advantages of subtenons

Back 7

- akinesia (better than topical)
- analgesia (rapid onset, similar quality to peri/retrobulbar)
- safety (no sharp needle in orbital cavity)
- can be used in those with globe length >26mm
- safe in anticoagulated patients
- avoids complications of needle blocks eg retrobulbar haemorrhage

Front 8

Disadvantages

Back 8

- chemosis is common
- subconjunctival haemorrhage
- incomplete akinesia (hard to block CN6 and orbicularis oculi - facial n)
-requires specialised equipment (lid retractor, westcott scissors and moorfields forceps) and specialised training

Front 9

contraindications to subtenons

Back 9

- scleral disease eg previous retinal detachment surgery, scleral adhesions prevent spread, previous subtenons, previous glaucoma surgery
- no consent
- red eye or infection
- cant lie flat
- persistent cough

Front 10

peribulbar block anatomy

Back 10

- retrobulbar cone formed by 4 rectus muscles (MR, LR, SR, IR)
- deposit LA outside cone, then diffuses into cone
- akinesia by blocking CN 3, 4 and 6 (trochlear hardest to block)

Front 11

how to perform

Back 11

- preamble as for subtenons
- lie patient flat
- topical anaesthetic eg amethocaine/oxybuprocaine
- locate junction outer 1/3 inner 2/3 of inferior orbital surface
- manipulate globe superiorly
- insert 25G 25mm needle attached to 10ml syringe with 1% lig, 1% ropi and 30units hyaluronidase/ml
- allow to fall under own weight to max depth 25mm
- after aspiration, inject 6-8mls of LA
- close eye and cover with patch with honans or simple massage
- assess akinesia, if unsatisfactory, supplement with remaining LA in medial canthus injection, dont go deep as ophthalmic artery continues medially

Front 12

complications of peribulbar block

Back 12

- retrobulbar haemorrhage (is suspect need urgent ophthal opinion and possible lateral cathotomy to release prressure
- globe perforation (ensure axial length <26mm as if greater increases risk of staphyloma)
- retrobulbar block

Front 13

assess block

Back 13

- bruising
- IOP (normal 10-15mmHg)
- facial nerve (orbicularis oculi)
- eye movements (hardest to block superior oblique from CN6)
- vision (1/3 no vision, 1/3 altered, 1/3 unaltered)

Front 14

indications topical anaesthesia

Back 14

patient
- motivated
- speak english
- not dense catataract

surgeon
- quick
able to tolerate poor akinesia

risk is increased risk of capsule tear
oxybuprocaine lasts 20mins

Front 15

retrobulbar haemorrhage

Back 15

- ophthal review
- lateral cathototomy
- honans balloon
- reduce ICP with mannitol, head up, acetazolamide

Front 16

Anticoagulant guidelines

Back 16

- anticoagulants and antiplatelets should be continued in those with prosthetic valves and coronary stents
- clopidogrel and aspirin should be continued
-warfarin should be continued and INR checked close to time of surgery
- both subtenon and needle techniques are equally ok with anti-platelet/anti-coagulants, but neither as safe as topic with intracameral

Front 17

Horner's syndrome causes

Back 17

- sympathetic block to cervical plexus, stellate ganglion or proximal brachial plexus
- cervical plexus invasion from apical lung tumour
- thyroid carcinoma and goitre
- migraine and cluster headache
- multiple sclerosis