10 - Cornea4 Flashcards
Terrien’s marginal degeneration
- who
- pathophys
Rare, men, 20-40yo
IDIOPATHIC non-inflammatory degeneration
Slowly progressive PERIPHERAL STROMAL THINNING -> perforation (15%)
Terrien’s marginal degeneration
-signs/symp
Signs: SUPERONASAL, bilateral, slowly progressive thinning, assoc vascularized pannus
Symp: asymptomatic; progression can cause irreg astig, decr VA
*Mooren’s can app similar but with overlying epi defect
Salzmann’s nodular degeneration
- who
- pathophys
Rare, females, 6th decade
Episodes of keratitis -> degenerative dz
Assoc with SIGNIFICANT CORNEAL INFLAMMATORY DZ (incl mgd, trachoma, phlyctenulosis, vkc, dry eye, ik)
-can also be idiopathic
Salzmann’s nodular degeneration
-signs/symp
Signs: HYALINE plaque deposits b/w epi and BOWMANS, classically app as mid-periph, elev, BLUE-GRAY or yellow-white nodular lesions
- can be uni/bilat, single/multiple
- often located within/adjacent to old corneal scar/pannus
Symp: asymptomatic; pain if RCEs develop, vision reduced if nodule is within visual axis
While limbal girdle of vogt
- epidemiology/hx
- signs/symp
Very common, age-related: 55% of pts 40-60, nearly 100% over 80
Bilateral chalk-like linear opacities of nasal limbus (3/9 o’clock)
Asymptomatic
*degen of collagen, sometimes with calcium
Band keratopathy
-pathophys/assoc condns
Ocular: trauma, chronic inflammation/ocular surf dz
- uveitis/JIA
- dry eye
- exposure k
Systemic: incr serum CALCIUM or PHOSPHORUS levels
- GOUT (check uric acid levels)
- hypercalcemia/hyperparathyroidism
- sarcoid
- renal failure (check BUN, creatinine)
Band keratopathy
-signs/symp
Signs: Ca2+ deposits on anterior surface of BOWMANS, app as white spots with SWISS CHEESE pattern, most concentrated within interpalpebral cornea
Symp:
- usually asymptomatic: Ca2+ plaques at 3/9 o’clock
- uncommon: plaques move centrally -> FBS, decr vision
Arcus senilis
- who
- pathophys
- signs
Most common corneal opacity: almost 100% over age 80
Higher incidence in males, black
Assoc with AGE, HIGH CHOLESTEROL
Lipid deposition BEGINS ON DESCEMETS -> bowmans -> stroma
Bilateral, symmetric, 1mm band in periph cornea with clear zone of separation to limbus
Unilateral is rare - assoc with CAROTID DZ on side WITHOUT the arcus
Younger than 50 assoc with incr risk of CAD (run lipid profile)
Crocodile shagreen
- pathophys
- signs/symp
Irregularly arranged folds of collagen
Signs: BILATERAL, GRAY-WHITE, POLYGONAL stromal opacities (“cracked ice” app)
-either:
—near BOWMANS layer = ANTERIOR
—near DESCEMETS membr = POSTERIOR
Symp: asymptomatic + benign
Corneal farinata
Bilateral “FLOUR DUST” deposits located in CENTRAL DEEP STROMA
Due to aging, AD condn
Asymptomatic
Corneal graft rejection
- how common
- type of response
- layers
30% within one year
TYPE 4 HS RXN
Epithelial: rare; elevated, irregular epi
Stromal: subepi infiltrates known as KRACHMER’S SPOTS
Endothelial: charac by WBCs on endo that form KODADOUST LINE
Refractive surgery
- absolute contraindications (4)
- relative contraindications (5)
Absolute:
- under 18 yo with unstable RE within last year
- unrealistic expectations
- ocular dz: keratoconus, active HSV, contact lens warpage
- systemic dz: CT dz (e.g. keloid formers), collagen vascular dz, immunocompromised (e.g. chronic steroid use)
Relative:
- ocular dz: blepharitis, dry eye, chronic eye rubbing, osd, large pupils
- diabetes mellitus - 3mo stability required
- POAG: if not well controlled, due to elevation during procedure with suction cup placement
- pregnancy
- retinal thinning/lattice degen: incr risk of retinal tears
Refractive surgery
-contact lens wearers need to be out of them how long prior
Soft spherical: 3-14 days
Soft toric + RGP: 14-21 days
Refractive surgery
-radial keratotomy
Radial incisions made with DIAMOND KNIFE to flatten peripheral stroma -> normal IOP pushes weakened area outward -> reduced myopia
NO LONGER PERFORMED due to better options
-significant instability, PROGRESSIVE HYPEROPIC SHIFTS
Refractive surgery -photorefractive keratectomy —procedure —candidates/tx range —healing
Removal of epi, BOWMANS, superficial stroma (no flap) -> excimer laser to cornea
-vs lasik: bowmans -does not regen, kept in lasik; less post-op dryness, requires less corneal thickness, cheaper
Ideal for PTS AT RISK FOR TRAUMA (military, athletes)
-no risk of flap complications
Tx range: -8 to +4D, up to 4D cyl
400um residual cornea reqd
Longer healing time (1-2 weeks) bc entire epi must regrow
- extremely poor vision + pain post-op (given nsaids, bcls)
- risk of stromal haze reduced with mitomycin C during procedure
Refractive surgery -LASIK —procedure basics —tx range/requirements —healing
Laser-assisted in situ keratomileusis
Epi flap made with MICROKERATOME -> excimer laser to ANTERIOR STROMAL BED -> flap reattached
Range: -10 to +4D, up to 5D cyl -clear lens extraction can be performed for those exceeding requirements Thickness requirements: 250um residual -flap itself = 150um -ablation depth = 12um per D
Heal faster (1-2 days), less pain + post-op haze vs prk
Refractive surgery
-LASIK
—femtosecond laser flap
Used instead of microkeratome
E.g. Intralase
FS flap: thinner (avg 100um), removes risk of mechanical malfunction, assoc with less post-op dry eye
Refractive surgery
- LASEK
- epi-LASIK
Laser epithelial keratomileusis
Same procedure as lasik, but flap is made with DILUTE ALCOHOL
Version of LASIK where a BLUNT PLASTIC BLADE creates the flap
Refractive surgery -conductive keratoplasty —who —procedure —tx range
PRESBYOPES, low hyperopes, residual astigmatism after previous sx
RADIO FREQUENCY energy to SHRINK COLLAGEN FIBERS in peripheral stroma -> central steepening
-regression expected in 2-3yrs, can be repeated
+0.75 to +3.00D, less than 0.75D cyl
Refractive surgery -intrastromal corneal rings (Intacs) —who —procedure —tx range
KERATOCONUS
PMMA rings inserted into peripheral stroma -> flatten cornea (shortens corneal arc length)
-0.75 to -3D (no hyperopes)
Refractive surgery
-clear lens exchange
—procedure
—tx range
Cataract sx without cataracts
No residual accomm remains (unless MFIOL used)
Large range
Refractive surgery
-phakic IOL
—procedure
—tx range
“Implantable contact lens”
Intraocular lens implanted in PHAKIC eyes
-angle-supported, iris-supported, or sulcus-supported
-requires a peripheral iridotomy
Large range of errors, preserves natural accomm
Refractive surgery
-astigmatic keratotomy
—procedure
Corneal incisions with DIAMOND BLADES to relax cornea in STEEPEST MERIDIAN
Refractive surgery
-wave-front guided/custom corneal surgery
—procedure
Reduces HOAs (coma, spherical) + corrects RE (LOAs) Can be done with LASIK/PRK - theoretically better contrast + acuity, less glare
Refractive surgery
-successes
Generally considered 20/40 or better
90-99% with low RE get this
~75% achieve 20/25 or better
Refractive surgery
-LASIK complications (9)
1) Pain in first 24hrs - wound, flap complications (severe)
2) serious infection - esp days 1-3, gram(+)/mycobacteria
3) flap complications
4) corneal ectasia - esp high myopes, anytime after sx
5) residual RE - esp > -8D, loss of BCVA in 1%
6) glare - small ablation zone, large pupil, monovision
7) dry eye - MOST COMMON SE (33%)
8) diffuse lamellar keratitis
9) epithelial ingrowth
Refractive surgery
-LASIK complications
—types of flap complications (4)
Button hole: cap perfortion/hole in flap, esp very steep corneas or deep set eyes
Free caps: no hinge made, esp very flat corneas
Flap folds: almost half occur in 1 hour, 95% within 1 week
- macrostriae = full-thickness with undulating, parallel stromal folds, slippage or mal-positioning during sx
- microstriae = fine, irreg, multi-directional folds in Bowmans, resolve on own
Flap dislodgement: more common with keratome flaps, due to accidental touch to eye/lid
Refractive surgery
-LASIK complications
—type of dry eye caused
Secondary, non-sjogren’s, aqueous-deficient due to corneal nerve severing
Often improves in 1-2mo
Refractive surgery
-LASIK complications
—diffuse lamellar keratitis
aka sands of the sahara
Rare, inflammatory, non-infectious reaction at the lamellar interface (b/w corneal flap + stroma)
Fine, granular, sand-like infiltrate 2-3 days after sx
May be response to toxins
-less common with disposable microkeratomes
Symp: asymptomatic; photophobia, blur, FBS, pain, vision loss (scarring/melt)
Refractive surgery
-LASIK complications
—epithelial ingrowth
Slow: 1mo post-op
Faint grey line or white, milky deposits within 2mm of flap-edge interface
Asymptomatic
MOST COMMON COMPLICATION ASSOC WITH LASIK ENHANCEMENT
Refractive surgery
-retreatment criteria
Earliest at 3mo, prefer 6mo
Astig: >0.75D + symptoms
RE: >/= 0.75D from target in unhappy pt
Uncorrected VA of 20/30 or worse in unhappy pt
