Ophthalmology Book

Vision Disorders

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Laser In-Situ KeratomileusisAka: LASIK

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  1. Indication
    1. Refractive Surgery to Correct Refractive Error
    2. Current Refractive Surgery procedure of choice
      1. Replaces Photorefractive Keratectomy (PRK)
      2. Replaces Radial Keratotomy (RK)
  2. Criteria for LASIK (and PRK)
    1. Age 18 years or older
    2. Stable Refraction for at least 1 year
    3. Myopia -0.50 to -12.00 diopters
    4. Hyperopia less than +6.00 diopters
    5. Astigmatism less than or equal to 5.0 diopters
    6. No contraindications below
  3. Contraindications to LASIK (and PRK)
    1. Ocular
      1. Keratoconus
      2. Herpetic Keratitis
      3. Progressive Myopia
      4. Corneal disease
      5. Glaucoma
      6. Cataract
      7. Corneal Scarring
      8. Dry eye
      9. Blepharitis
    2. Medical
      1. Uncontrolled vascular disease
      2. Autoimmune disease
      3. Immunocompromised status
      4. Pregnancy or Lactation
      5. Keloid formation history
      6. Diabetes Mellitus
  4. Technique
    1. Microkeratome creates thin flap (160 u) in Cornea
    2. Computer programmed prior to surgery
      1. Corneal topography
      2. Refraction
    3. Pre-programmed excimer laser reshapes Cornea
      1. Laser emits UV light at Cornea (photoablation)
      2. Etches away Corneal Stroma under flap
        1. Myopia: Laser flattens central Cornea
        2. Hyperopia: Laser flattens peripheral Cornea
        3. Astigmatism: Laser flattens steepest Meridian
      3. Results in little to no adjacent thermal damage
    4. Recent advances in laser beam technology
      1. Smaller laser beam width <100 u
      2. Eye tracking systems adjust for eye movement
    5. Corneal flap repositioned without Suture
    6. Both eyes may be corrected on same day
    7. Vision recovered within 48 hours
  5. Discharge medications
    1. Topical Corticosteroid eye drops
    2. Topical antibiotic eye drops
    3. Topical NSAID eye drops
    4. Eye shield use overnight following surgery
  6. Follow-up
    1. Routine postoperative follow-up evaluations
      1. Day 1
      2. Week 1
      3. Month 1,3 and 6
    2. Warning signs necessitating follow-up
      1. Decreased Visual Acuity
      2. Suspected infection (redness)
      3. Pain
        1. Epithelial abrasion
        2. LASIK flap complication
  7. Efficacy
    1. Uncorrected vision 20/20 achieved
      1. Low Myopia (<7 D): 60% (as high as 67-83%)
      2. High Myopia (>7 D): 45%
    2. Uncorrected vision 20/40 achieved (ok for driving)
      1. Low Myopia (<7 D): 90% (as high as 97-100%)
      2. High Myopia (>7 D): 85%
  8. Advantages over other procedures (contrast with PRK)
    1. Minimal pain
    2. Quick visual recovery
    3. Treats high levels of Myopia
    4. Both eyes treated on same day
    5. LASIK enhancements easily performed within 12 months
    6. No stromal haze (unlike PRK)
    7. Satisfaction rate of 90% (PRK has 52% satisfaction)
  9. Adverse Effects
    1. Minimal post-operative discomfort
    2. Glare or halos associated with outdoor lights
      1. Usually resolves within months
    3. Dry eyes for first 3 months after surgery
      1. Related to Corneal nerve innervation
      2. Treat with artificial tears (no preservative) prn
  10. Complications
    1. Repeat surgery to reshape Cornea: 5-30%
      1. Overcorrection or undercorrection
      2. Irregular Astigmatism
    2. Corneal Epithelium growth beneath flap: 1%
    3. Vision threatening infection: 1-5 per 10,000 procedures
    4. Best spectacle-corrected vision worse than 20/40: <0.5%
    5. Corneal flap displacement: 0.5% (usually repairable)
    6. Buttonhole tear in Corneal flap precluding surgery
    7. Diffuse lamellar Keratitis (Sands of Sahara Syndrome)
      1. Sterile inflammatory response
  11. Precautions
    1. Does not correct accommodation loss with aging
    2. Reading glasses will still be required
  12. References
    1. (1999) Med Lett Drugs Ther 41(1068):121
    2. Bower (2001) Am Fam Physician 64(7):1183
    3. Perez-Santonja (1999) Ophthalmology 106:21
    4. Waring (1999) Invest Ophthalmol Vis Sci 40:S588
    5. Stulting (1999) Ophthalmology 106:13

Keratomileusis, Laser In Situ (C0752094)

Definition (MSH)A surgical procedure to correct MYOPIA by CORNEAL STROMA subtraction. It involves the use of a microkeratome to make a lamellar dissection of the CORNEA creating a flap with intact CORNEAL EPITHELIUM. After the flap is lifted, the underlying midstroma is reshaped with an EXCIMER LASER and the flap is returned to its original position.
ConceptsTherapeutic or Preventive Procedure (T061)
EnglishLaser assisted in situ keratomileusis, Laser Assisted Stromal In Situ Keratomileusis, Laser In Situ Keratomileusis, Laser Intrastromal Keratomileuses, Laser Intrastromal Keratomileusis, LASIK
Spanishqueratomileusis in situ asistida con láser, queratomileusis in situ asistida con laser
CreditsDerived from the NIH UMLS (Unified Medical Language System)



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