Ocular anesthesia

There are two types: 

A. Local

B. General

A. Local anesthesia:- 

1. Topical
2. Intracameral
3. Infiltration
4. Nerve block

↔️INDICATIONS:- 

• Cataract surgery
• Pterygium excision
• Surgery for glaucoma
• Minor extraocular plastic surgery
• Keratoplasty
• Dacryocystorhinostomy
• Minor Anterior segment procedure
• Refractive surgery
• Vitreo-retinal surgery

B. General anesthesia:- 

1. Retrobulbar
2. Peribulbar
3. Subtenons
4. Subconjunctival

↔️INDICATIONS:- 

• In children & infant
• Mentally retarded
• Anxious & uncooperative
• Patient preference

✅LOCAL ANESTHESIA:- 

⬆️ADVANTAGE:- 

• Patient is conscious & alert
• Drug used in GA can be avoided
• Systemic complications is less.

⬇️DISADVANTAGE:- 

• Painful
• Difficult in uncooperative patient

🟢LOCAL ANESTHESIA

A. TOPICAL ANESTHESIA

B. INFILTRATIVE ANESTHESIA

A. TOPICAL ANESTHESIA:- They work by stabilizing the nerve membrane potential temporarily,so that it can't be depolarized. They are:

1. Lignocaine hydrochloride (4%& ,2%)
2. Tetracaine 0.5%
3. Proparacaine 0.5%
4. Amethocaine 0.5%
5. Cocaine (2%-4%)- also causes mydriasis.

⭐ Amethocaine & proparacaine are less potent but are less damaging to the corneal epithelium.

So, they are used in tonometry & gonioscopy.

⭐ Nowadays most adult cataract & refractive surgery & other small surface procedure done under topical anesthesia using lignocaine, proparacaine or with tetracaine drops X 3 times X 5 minutes before surgery.

B. INFILTRATIVE ANESTHESIA:-

Motor & sensory block are obtained by infiltration of anesthetic agents in and around the eyeball.

They may be facial block (to paralyze orbicularis oculi muscle):

• Retrobulbar block
• Peribulbar block
• Regional block

🔶 COMPONENTS FOR BLOCK:- 

A. LIGNOCAINE (2%):- Onset of action- 10-35sec; Duration of action- 15-20 min.

B. Bupivacaine (0.5%) :- a long acting local anesthetic agents usually mixed with lignocaine.  50:50 ratio to achieve better & prolonged anesthetic effect. 75-90 min duration of action. 

C. Adrenaline:- prolong the effects of anesthesia by including vasopasm in the injected area, but with slower action. It also reduces the chance of bleeding during surgery especially in oculoplast procedure.

D. Hyaluronidase:- enhances the dispersion & absorption of local INFILTRATIVE anesthetic agents. The increased dispersion makes possible, a more effective motor block , but it limit the duration of anesthetic effect.