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Ophthalmology - Coggle Diagram

- - - - Frontal, zygomatic, ethmoid, maxilla, sphenoid, lacrimal, palatine
    - - Contain - vascular tissue, neurological tissue and adventitia
      - Optic canal - optic nerve, meninges, ophthalmic artery
      - Superior oribita fissure - CN 3,4,6, ophthalmic division of trigeminal, superior ophthalmic vein
      - Inferior orbital fissure - maxillary nerve and zygomatic branch, ascending brances of ptergopalatine ganglion, inferior ophthalmic vein
      - Anterior and posterior ethmoid foramina - ethmoid nerves and vessels
    - - Globe, orbital fat, muscles, nerves, vessels, lacrimal apparatus
  - - - Nasocillary nerve - sensation to cornea, perilimbal conjunctiva & superionasal peripheral conjunctiva, pass intra-conally - supplies long and short cillary nerves
      - Lacrimal & frontal nerves provide sensory supply to rest of peripheral conjunctiva - pass extra conally
      - Sensory via ophthalmic branch of trigeminal - 3 branches pass through superior orbital fissure
      - Optic nerve leave globe posteromedially, passes through orbit and exits via optic foramen - vunerable to injury with long (38mm) retrobulbar needles
    - - Pass within cone and supply recti at intra conal surfaces
      - Trochlear nerve follows and extra conal path - so may be spare with intra conal technique -> SO not blocked
      - Oculomotor & abducens nerve enter via the superior orbital fissure
- - - - Allergy to LA
      - Localised sepsis
      - Pt refusal
    - - Communications issues
      - Postural difficulties
      - Poor compliance with instructions
      - Confusion
      - Inability to lie still
      - Grossly abnormal coagulation
      - Perforated globe/ trauma
  - - - Chemosis - swollen conjunctiva
        
        Risks - malpositioned sub-tenon's
        
        No Rx needed
      - Sub-conjunctival haemorrhage
      - Pain
    - - Retrobulbar haemorrhage
        
        Arterial - sudden onset proptosis, raised IOP, reduced acuity - can be sight threatening
        
        Venous - slow onset with less pressure effects - less likely sight threatening
        
        Treatment
        
        Conservative
        
        External pressure, acetazolamide, mannitol
        
        Surgical
        
        Emergency lateral canthotomy, cantholysis or orbital decompression
      - Globe injury
        
        Sudden pain and acuity change
        
        Can threaten sight
        
        Emergency ophthal r/v
      - Ecchymoses
      - Optic nerve atrophy
        
        Altered acuity
      - Muscular palsy
        
        Diplopia/ptosis
        
        Limitation of gaze
        
        Rx via cause - can be limited
      - Brain stem anaesthesia
        
        Altered neurology - CVS/RS comprimise
        
        Life threatening
        
        Supportive Mx
  - - - Pt looks up and out to expose infero-nasal quadrant
      - Non tooth forceps are used to take a bite of conjunctiva and Tenon's fascia
      - Following topicalisation, Barraquer speculum inserted to keep eye open
      - Small cut with Westcott scissors to expose sclera, scissors then passed around globe to create a passage
      - Sub-Tenon needle attached to syringe passed through passage, following contour of the eye ball until syringe is vertical
      - LA injected posterior to equator of globe ~ 3-5ml
      - Uses
        
        Cataracts, VR surgery, trabeculectomy & strabismus
      - Advantages
        
        Blunt needle reduces risks of retrobulbar haemorrhage and globe perf
        
        Less painful than sharp needle techniques
      - Disadvantages
        
        More chemosis and echyymoses
    - - Following topicalisation - neutral eye position, perconjunctival puncture is made in the far infero-temporal corner of the eye
      - Needle is passed posteriorly parallel to floor of orbit until past equator - 5-10ml LA after -ive aspiration
      - Pts may complain of pressure like headaches - resolve after a few minutes
      - Provides similar level of akinesis and anaesthesia and sub-Tenon's
    - - Instillation of LA (tetracaine, metacaine or lidocaine)
      - Few drops to surface, 5-10min before operation
      - Low risk of epithelial damage but usually reversible
      - Block trigeminal nerve in cornea and conjunctiva - no anaesthesia to intraoccular structures nor akinesia
    - - Puncture @ junction of lateral 1/3 and medial 2/3 of lower obrbital ridge - needle passed parallel to orbital floor
      - Once past equator - needle angled medial and superior 45 degress and passed further to enter intraconal space - 2-4 ml LA
      - Proptosis on injection
      - Risks
        
        Highest of all blocks and less well tolerated by pts
        
        Globe perf, optic nerve injury
      - Advantages
        
        Best akinesa
    - - Via surgeon intraoperatively
      - Direct injection into the AC
- - - - Avoid N2O if intraoccular gas bubble
        
        Gas bubbles can last up to 3 months..
- - - - Topical anaesthesia +/- intracameral injection
    - - MDT approach ?bridging etc