3. Cataracts 3 Flashcards
(27 cards)
What are the two older cataract surgery techniques?
- Couching
- Needling
Couching
* pushing backwards of lens (surgical subluxation)
* may be used in 3rd world (Arabia, Africa)
* Complications: need aphakic correction; glaucoma, uveitis, optic atrophy.
Needling
* useful for soft/ young cataracts
* rupture of capsule with fine needle
* Complication: foreign material can produce an inflammatory response
* Limited application in adults
What are the 2 types of lens extraction techniques? What are their differences?
- Intracapsular cataract extraction (ICCE) → breaks zonule, take lens out
- Extracapsular cataract extraction (ECCE) → leaves the capsule & only take out the contents of the lens; conventional expression (hard lens) or phakoemulsification (phako)
What are the 4 main types of ocular anaesthetics? What technique uses which?
- General (ICCE) → rare
- Local (ICCE & ECCE) → retrobulbar or peribulbar
- Topical (phaco) → alcaine drops
- Topical & intraocular mydriatics
IntraCapsular Cataract Extraction ICCE process
1. Large cut made superiorly (4-6 o'clock)
2. Injection of ` α-chromotrypsin to break the zonules
3. Lens removal via cryoprobe/ forceps`
Disadvantages:
* requires a large surgical cut (12-20mm)
* No capsule/ bag to carry the IOL → anterior chamber IOL; can cause vitreous prolapse and retinal detachment due to lack to structure in front of the vitreous.
ExtraCapsular Cataract Extraction ECCE process
* requires a smaller cut (3-5mm)
* retains a normal vitreous ∴ less prone to retinal detachment
* anterior capsule is torn via capsulorhexis
* mechanical removal of lens material, leaving the capsule behind
* Phacoemulsification to divide and conquer the lens
What is phacoemulsification?
A phako is a high speed agitator at 40kHz that help divide the len into 4 parts (divide & conquer). Afterwards a suction device helps vacuum up the cortex. This is therefore also called a “jack hammer with vacuum cleaner”
What is the disadvantage of wound closure with sutures after ECCE and ICCE surgery?
- Cut will reduce corneal curvature
- Sutures can pull on cornea which increaes curvature and therefore creates astigmatism
- Incision causes ATR (90º)
- Tight suture causes WTR (180º)
- ∴ req balance between suture and incision
Which type of cataract sx can utilise sutureless wound closure? How is this done?
ECCE only
* Induce oedema of the cornea. Swelling of the cornea pushes the incision close
* However there is no control of resultant astigmatism
What are the 3 cataract surgery complications commonly caused by sutures?
- Suture irritation → GPC
- Tight suture → high astigmatism (>2.5D) → consider removal of sutures after 3 months
- Leakage → Siedel test for NaFl streaming
How much dioptres of vision is induced by aphakia?
10-12D hypermetropia
What are the 3 correction methods for aphakia?
- Spectacles - least preferred
∵ reduced FOV, large magnification, prismatic effect, BV problems & aniesokonia if uniocular - CL - extended wear
- IOL - most preferred
→ use A-scan, refraction & corneal power to determine IOL power (plastic nowadays)
What are the 2 components in an intraocular lens implant?
- Optic
- Haptics
What are the 3 types of IOLs?
Anterior chamber → get tissue chaffing ∴ only used if zonules are broken/ weak
* Iris fixed
* AC angle fixed
Posterior chamber
* in the bag/ capsule = best location & optics
* sutured in the sulcus
What are the 4 different IOL designs?
- Single vision/ Astigmatic
- Multifocal/ simultaneous focus
- Extended focus
- Movable IOL
What is pars plana lensectomy?
- A cataract sx approach from behind the iris.
- Incision is made behind the limbus thorugh the sclera
- This requires general anaesthetic
- May involve vitrectomy
- reserved for complicated cases e.g. ECCE complication, trauma, congenital cataract, diabetic
What is the role of a Femtosecond Laser in cataract surgery? What are the benefits (2) and disadvantage (1) of this?
Femtosecond Laser can be used to make the incision, create capsulorhexis and “divide & conquer” the nucleus
Adv: better centration of capsulorhexis; require less energy from phaco
Disadv: surgery is more expensive
What are the 4 general surgical complications of cataract sx?
- Capsular tear/ rupture → nucleus drops into vitreous
- Zonular breaks → drop lens into vitreous
- Iris damage
- Wound leak → Seidel’s sign ∴ may req sutures
How can presbyopia be managed with or after cataract sx? (3)
- Monovision IOL → suitable for low adds up to +1.50DS; high add may induce suppression
- Multifocal IOL
- Use of reading glasses + Distance SV IOL
What are the post surgical drops regime after cataract sx?
- Topical antibiotics → chloremphenicol or fluoroquinolone QID 1/52
- Topical steroids → Prednisolone forte or dexamethazone QID 1/52, TID week 2, BID week 3, QD week 4
What is the followup schedule post cataract sx?
1d, 7d, 21d, 6wks, 12wks, yearly
What are the 9 common early (<1 month) complications of cataract sx?
- Ptosis w/ local injection (12-15% but reduces by 4 wks)
- Pupillary block with ICCE (vitreous, YAG)
- Wound leak (Seidel, low IOP)
- Toxic Anterior Segment Syndrome (TASS)
- Endophthalmitis (<0.05%)
- Perceived glare arcs or haloes → dysphotopsia
- Anterior chamber debris
- Corneal striae - Bullous keratopathy
- IOL displacement
