Irregular cornea Flashcards
Aims of Refractive surgery
Better unaided vision Less reliant on specs/cls Enhance sports/performance Cosmetics Self esteem Solve cl wear failures
LASIK
Laser assisted in-situ keratomileusis
Corneal flap cut with microkeratome Laser reshapes exposed stroma Replace flap Sutures not required Bowmans layer preserves
LASIK complications
Decentred ablation Photophobia Glare/haloes Rx issues Poor microkeratome cut Flap issues
PRK
Photo-refractive keratectomy -process
Argon fluorine laser - 193nm
High photon energy breaks monocular bonds
Precise tissue removal
Min thermal damage to adjacent tissue
PRK complications
Topo changes - central islands
Decentred ablation
Over/under correction
Rapid regression
LASEK
Laser assisted sub-epithelial keratectomy
Combines benefits of lasik/prk
Outer cornea lifted - using numbing drops/alcohol solution /fine blade
Laser reshapes remaining corneal surface
More pain/discomfort > lasik
Less pain < prk
Radial keratotomy RK
Myopia reducing surgery
Series deep, mid-peripheral radial incisions
- 4-8, 90% depth
Flatten corneal curvature
Rk complications
Corneal perforation Incision extended into limbal/optic zone Intersecting incisions Recurrent corneal erosions Increased astigmatism Reduced BCVA Diurnal variations Myopic/hyperopic shift
INTACS
Mechanical correction device - PMMA 9-10m diam Thickness 0.2-0.45mm - dictates refractive effect Inserted in peripheral stroma 2/3 corneal depth 4D myopia limit
INTACS indications
16+yo K<60d Corneal thickness >400u Absence of corneal disease Flattening steepest k by 1.5-2.5d
Complications for INTACS
Peripheral corneal haze poss
Lamellar channel deposits common
Deep stromal vascularisation common
Corneal pannus common
Penetrating keratoplasty - PK
Abnormal cornea replaced with healthy donor
Full thickness graft
Indications for pk
Cosmetic
Structural
Therapeutic
Optical
Early complications PK
Shallow AC Iris prolapse Persistent epithelial defects Infection Primary graft failure Wound leak Increased IOP
Later complications pk
Astigmatism Glaucoma Cataract Graft failure/rejection Graft infiltrates Recurring corneal issues
Graft rejection
Most common in PK Risk greatest in 1st yr Assoc with glaucoma RSVP - redness - sensitivity to Light Vision drop Pain
DALK
Deep anterior lamellar keratoplasty
Lamellar graft
Treat corneal disease upto endothelium
- KC/stromal scars/some corneal dystrophies
Requires sutures
Unpredictable refractive outcome - irregular astigmatism/anisometropia
DALK pros
Faster wound recovery Faster visual rehab Fewer wound related issues Better preserves ocular integrity Earlier suture removal
Endothelial keratoplasty EK
Endothelial disorders
- Fuchs / bullous keratopathy
EK process
Diseased DM/endothelium stripped
Donor tissue transferred to AC
Donor tissue unfolded - attached to posterior stroma using air bubble
Sutureless
EK pros
Sutureless - avoid suture issues Preserves structural integrity Reduced wound healing issues Major refractive changes avoided Rapid healing
EK cons
Anterior corneal irregularities -> reduced va Anterior stromal collagen disruption Reduced BCVA Monocular diplopia/ghost images Sub-epithelial fibrosis (diffusive)
