Day 4 (3): Cataract Surgery Flashcards
Define Visual Impairment.
BCVA: 20/70 - 20/400
Major causes:
1. Refractive Errors: 43%
2. Cataract: 33%
3. Undetermined
Define Blindness.
BCVA > or worse than 20/400
Major causes:
1. Cataract: 51%
2. Undetermined: 21%
3. Glaucoma: 8%
Risk factors for cataract formation.
- Aging: people are living longer than they used to
- Race: African American
- Sex: Female
- Smoking
- Low educational status
Indications for ELECTIVE surgery.
- Patient’s desire or request
- not based on a specific VA
- determine if VA will improve significantly with surgery - Reduced visual function starts to interfere with ADL or job
- Dense cataract obscuring the fundus
- preventing examination and treatment of another eye condition - Loss of stereopsis or depth perception
- requires binocularity
- lost even if only one eye has cataract - Decreased peripheral vision
- Disabling glare
- difficult to drive
- Nuclear and Posterior Subcapsular Cataract - Symptomatic anisometropia
- unequal refractive powers of the eyes
- cataractous lens is thicker –> more myopic –> harder to correct if only one eye is involved esp. if grade difference is 200-300
Indications for EMERGENCY surgery.
- Phacolytic glaucoma
- Phacomorphic glaucoma
- Phacoantigenic uveitis
- Anterior dislocation of the lens
- due to weakened zonules
What is the Phaco Trinity?
- Cataractous lens (increased AP diameter, opaque to colored)
- Phaco machine
- Phaco handpiece
What are the types of cataract?
- Nuclear: nucleus
- later onset (60-70 yo)
- myopic shift due to thicker nucleus –> near vision better even with presbyopia or loss of accommodation –> discoloration of lens –> BOV
- loss of blue/yellow color perception and contrast sensitivity - Posterior Subcapsular: cortex anterior to posterior capsule
- earlier onset (40-60 yo)
- glare
- monocular diplopia: does not resolve with only one eye open
- blurred central vision + clear peripheral vision - Cortical: cortex
- earlier onset (40-60 yo)
- glare
- monocular diplopia
- blurred central vision + clear peripheral vision
How is anesthesia given to patient undergoing cataract surgery?
Routine: TOPICAL + INTRACAMERAL (to anesthetize the AC structures)
- (+) mydriasis if with intracameral: paralysis of iris sphincter
- A: NO patch and NO risk for orbital injury
- D: Harder case; may cause epithelial toxicity (use OVD)
- if long OR: add Bupivacaine (longer-acting anesthetic)
- Retrobulbar: behind the globe into the muscle cone
- (+) akinesia: paralysis of EOMs
- (+) proptosis: injection behind causes anterior displacement
- (+) mydriasis
- Patching post-op due to ptosis from akinetic LPS
- A: for starting surgeons, total anesthesia, easier case
- D: MORE risk for globe perforation, ON injury, muscle damage, retrobulbar hemorrhage - Sub-Tenon: beneath Tenon’s capsule
- (+/-) akinesia
- (+/-) mydriasis
- A: NO risk of ON injury, LESS risk of muscle damage and globe perforation, easier to do
- D: (+) chemosis and congestion, need to patch post-op - Peribulbar: posterior to conjunctiva with a cannula
- (+/-) akinesia
- A: NO risk of ON injury, LESS risk of globe perforation
- D: Hard to get good block, (+) chemosis, need patch post-op - IV/General: for pts who don’t like injections
- put on LIGHT sleep only
- DEEP sleep –> Bell’s Phenomenon: globe turns superolaterally
ECCE vs ICCE
INTRAcapsular Cataract Extraction
- WHOLE lens + capsule removed
EXTRAcapsular Cataract Extraction
- Anterior capsule + cortex + nucleus removed
- Posterior capsular bag left in place for IOL implantation
Phacoemulsification
- Special kind ECCE using ultrasound to break-up lens material
- Applicable for most cataracts
- A: Quick visual rehabilitation
- P: Specialized and expensive equipment; heat generated can damage endothelium
What are the indications, advantages and disadvantages of ICCE?
Indications:
1. Subluxated lens: weak zonules; treatment of choice
2. Cataract with Pseudoexfoliation syndrome: weak zonules
3. Brunescent cataract
Remember: Maneuvers done to remove lens material during ECCE/Phaco is NOT POSSIBLE with weakened zonules
Advantages:
1. NO risk of secondary cataract: entire lens removed
2. Less equipment needed vs phaco
Disadvantages:
1. High complication rates
2. Risk of vitreous loss
- due to removal of posterior capsule (loss of barrier between A and P segments)
- retinal detachment: vitreous tugs on the retina at attachment sites
- corneal edema: when vitreous or cryoprobe comes into contact with endothelium
3. Astigmatism due to LARGE corneal incision and suturing
- to allow removal of entire lens
4. Prolonged visual rehabilitation
5. Left aphakic with very THICK glasses or with ACIOL or sutured IOL
What are the indications, advantages and disadvantages of ECCE?
Indications:
Very hard lenses where Phaco would be technically more difficult
Advantages:
1. Smaller incision than ICCE
- May be self-healing or needing less sutures
- Lesser risk of induced astigmatism
- More stable and secure incision
2. Posterior capsule left in place
- Intact barrier that prevents dislodgement of VB anteriorly, admixing of AH and VB, and bacterial access to the vitreous cavity
- Less risk of intraoperative vitreous loss, retinal detachment, CME
- Prevents vitreous adherence to the iris, cornea and wound causing synechiae formation
- IOL implantation in a better anatomical position
3. Less trauma on the corneal endothelium = less corneal edema
- No heat generated vs Phaco
- Smaller incision vs ICCE
4. Least equipment needed
Disadvantages:
1. Still with risk of astigmatism albeit smaller vs ICCE
2. Longer visual rehabilitation vs Phaco
What is Irvine-Gass Syndrome?
Pseudophakic Cystoid Macular Edema
- one of the most common causes of vision loss after cataract surgery
- due to upregulation of inflammatory mediators in the AH and VB post-surgery causing a breakdown of the BAB and BRB
- increased vascular permeability leads to extravasation and collection of fluid BETWEEN OPL and INL
Risks:
- ICCE: 60%
- ECCE: 15 - 30%
- Phaco: 0.1 - 2.35%
What two developments paved the way for phacoemulsification?
- Ophthalmic Viscosurgical Devices (OVDs)
- decreased incidence of corneal edema due to inadvertent trauma to the corneal endothelium from the smaller incisions of ECCE
- insulates the corneal endothelium from the heat generated by Phaco - Foldable Intraocular Lenses (IOLS)
Where else are OVDs used and what is its purpose?
- Cataract surgeries
- Corneal surgeries
- Anterior segment reconstructions
- Glaucoma surgeries
Purposes:
- Coats and protects ENDOthelium (dispersive)
- insulates from heat generated by Phaco
- prevents inadvertent touching and trauma by instruments and IOL - Coats and protects EPIthelium (dispersive)
- prevents drying - Maintains space (cohesive and viscoadaptive)
- deepens anterior chamber and keeps anterior capsule flat and taut for easier capsulorhexis
- dilation of small pupils
- allows maneuvers and tissue manipulation - Tamponades intraocular hemorrhage
- Seals posterior capsule rents preventing vitreous loss
What are OVDs made of?
- Sodium hyaluronate (NaHA)
- Provisc, Healon
- Viscoat (+ Chondroitin sulfate)
- Sodium salt of hyaluronic acid, a glycosaminoglycan
- Naturally found in the body, thus: biocompatible, non-inflammatory and non-pyrogenic
- From rooster combs
- Half-life: 24 hrs (AH), 72 hrs (VB) - Chondroitin sulfate
- Viscoat (+ NaHA)
- Sulfated GAG
- Primary mucopolysaccharide of the cornea
- BEST for endothelial protection
- Naturally found in the body, thus: biocompatible, non-inflammatory and non-pyrogenic
- From sharks fin
- Half-life: 24-30 hrs - Hydroxypropylmethylcellulose (HPMC)
- Aurovisc
- Cheapest, easily available and prepared
- Cellulose thus of plant origin
- Not naturally occurring: NOT completely metabolized, (+) risk for bacterial contamination and PRO-inflammatory
- Ensure complete removal post-op
How are OVDs classified according to physical properties?
- Cohesive
- more solid: maintains space and pressure - Dispersive:
- more liquid: coats and partitions - Viscoadaptive
- properties of both
What are Cohesive OVDs?
- Provisc, Healon (both made of NaHA), Amvisc
- High molecular weight
- High surface tension –> adherent to each other
Advantages:
1. Deepens and maintains AC
- deep AC = flat iris = flat and taut anterior capsule = easier capsulorhexis
2. Opens capsular bag for IOL insertion
3. Enlarges and maintains pupil size
4. Easily aspirated
Disadvantages:
1. Can accidentally come out of the eye easily as a whole
2. Poor coating ability for protection of endothelium
3. Can block TM and cause elevated IOP post-op if not removed completely
What are Dispersive OVDs?
- Viscoat (NaHA + CS), OcuCoat
- Low molecular weight
- Low surface tension –> disperses and spreads
Advantages:
1. Good coating capability: especially for corneal endothelium
2. Good lubricant for IOL insertion and epithelium
3. Holds vitreous back if with weakened zonules and capsular rent
Disadvantages:
1. Can’t maintain space well
2. Prone to bubble formation
3. May fragment into smaller pieces –> obscure posterior capsule + harder to aspirate and remove post-op
When are the different kinds of OVDs indicated?
Cohesive:
1. Maintain deep AC for capsulorhexis
2. Opening and maintaining capsular bag for IOL insertion
3. Easy removal post-op
4. Pt’s with shallow AC and floppy irises
5. Pt’s with small pupils
Dispersive:
1. Coating and protection of endothelium from heat and trauma
2. Coating and protection of epithelium from drying
3. Pt’s with compromised corneal endothelium
4. Pt’s with very dense cataracts requiring more phaco energy to emulsify = more heat generated
5. Pt’s with posterior capsular rents
What are Viscoadaptive OVDs?
- Healon 5
- Exhibits properties of both cohesive and dispersive OVDs
- Low flow rates: Cohesive to maintain spaces
- High flow rates: Dispersive to coat and protect endothelium
