Refractive surgery Flashcards
How does LASIK work
- Thin flap created in cornea (epi, bowmans, anterior stroma) –> folded back to expose central stroma
- laser ablates stromal tissue (create new cornea shape)
- flap replaced onto eye (self seals)
Difference between microkeratome vs. Femtosecond laser (LASIK flap creating)
Microkeratome: thicker flap, fast
- complications: partial flaps, free caps
Femtosecond laser: thin flap, uniform, less suction
- complications: flap oedema, transient light sensitivity
Which px are at risk when considering LASIK
- V steep or flat corneas (myopic <36D, hyperopic >49D)
- px with corneal ectasia/ scarring/ thin, active pathology
What is the LASIK post-op regime?
- (ophthal: day 1) Optom: week 1, month 1, month 3, month 6
- Meds: Ciprofloxacin (fluoroquinolone) + pred forte qid, 7 days
- do not rub eyes + eye shield (7 days) , regular non-preserved lubricants q1h (48hours), q2h for 1 month, qid 3/12
What are some intra-operative (95%) complications associated with LASIK?
- Microkeratome induced (flap complications): button-hole, incomplete flap, free cap, variable thickness/irregular cut, interface contamination
- Laser induced: initial oedema/ inflammation, transient light sensitivity syndrome
- epithelial defects (<1%): treat like corneal abrasion (BCL overnight, antibiotics, lubrication), increased risk of DLK and epithelial ingrowth
What are some post-op (5%) complications associated with LASIK?
- Flap striae (common in eye rub, high myopia)
- Diffuse lamellar keratitis = “Sands of sahara” = inflammation of stroma (tx: 1% pred forte q1h for 2 days, taper for 3-4 weeks), severe - irrigate w steroid
- Infectious keratitis (tx: chloramphenicol)
- Epithelial ingrowth (epi cells growing into flap interface)
- Posterior segment (RD, choroidal neovasc, mac haem)
- residual rx error
- corneal ectasia (mx CXLs, RGPs)
- Dry eye
What is the process of PRK and LASEK (surface ablation techniques)
PRK (photo-refractive keratectomy) - debride corneal epithelium –> laser excimer onto stromal surface
LASEK (laser-associated sub-epithelial keratectomy)- epithelium retained, alcohol weakens epi cells –> epi layer folded out of laser tx field and folded back after corneal re-shaping
Indications for PRK and LASEK
- Mild-mod rx + thin cornea (if concerned about corneal ectasia)
- recurrent erosions/ epithelial basement membrane disease
- Predisposition for trauma (bc no flap)
Post-op care for LASEK and PRK
- bandage CL 1 week
- topical corticosteroid qid (approx 12 weeks) + topical antibiotic qid
- acular bid (day of sx and 1 day post-op) = NSAID
- ## lubricants q1h
Compare LASIK vs. PRK
LASIK: less inflammation, faster recovery, maintains central cornea epithelium, corneal flap (weakens cornea, increases corneal denervation)
PRK: longer recovery, high infection risk, increased post-op discomfort, no flap-related complications, decreased rate of dry eye, easier refractive enhancement
Indications for Phakic IOL (surgically implanted CL)
- IOL in front of lens High myopic rx error (-5 to -20) pre-presbyope high myope, deep AC, good endo cell count, no cataract - no ectasia risk, better VA than laser procedures (high myope) - 3 types available
Risks associated with phakic IOL
- similar to cataract sx
- IOP rise, CME, endophthalmitis, hypopyon, hyphaema, corneal oedema, RD, cataract
Post-op care for phakic IOLs
- topical antibiotic + corticosteroid qid (3 weeks)
- avoid eye rub , makeup, swimming
review schedule: 1 day, 1 week, 1 month, 3 months
Considerations for refractive lens exchange (= removal of lens for refractive purpose)
Indications: mod-severe myopia, hyperopia
- not in px <50 years, RD risk in high myopes
Candidates: cataract, high hyperopia, low astig, needing to decrease IOP
