Corneal Surgeries PDF

MUST KNOW corneal thickness in each surgery! Corneal Wound Healing Phases 1st Latent Phase (First 6 hr) ○ Reduction of intracellular junctions ○ Infiltration of neutrophils ○ Apoptosis of keratinocytes (starts losing attachment to basal membrane) ○ What type...

MUST KNOW corneal thickness in each surgery! Corneal Wound Healing Phases 1st Latent Phase (First 6 hr) ○ Reduction of intracellular junctions ○ Infiltration of neutrophils ○ Apoptosis of keratinocytes (starts losing attachment to basal membrane) ○ What type of tight junction is between the basal cells and basal membrane? (Boards ?) Hemidesmosomes 2nd Migration Phase (6-36 hr post-injury) ○ Epithelial cells migrate to close the gap ○ Start adherence to the BM ○ Primary wave 18 hr and secondary wave 30 hr of neutrophils containing AMPs into the stroma 3rd Proliferation Phase (36-48 hr) ○ Basal cells from columnar layer proliferate to become wing and then superficial cells 4th Attachment Phase (48 hr) ○ Cells adhere firmly to the BM, intercellular junctions increase AMP (antimicrobial-peptide) in the tear film is present in all the process of wound healing ○ CAB37 protein Corneal Scarring Severe chronic inflammation (lymphocytes and neutrophils) leads to excess of fibroblast, collagen and fibrocytes -> scarring -> low VA Unorganized, makes a mix of themselves, opacities in cornea and will see white Epithelium regenerates every 48 hours Opacity or scar in central cornea -> decrease in VA Amniotic Membrane (heals great for superficial stroma lesions and epithelium) Biological treatment (Bio-tissue) for regeneration of the cornea ○ Decrease inflammation, scarring and angiogenesis Prevents neovascularization ○ Thick BM (inner layer of placenta) ○ Contains collagen and proteins as: Fibronectin, laminins, proteoglycans, and glycosaminoglycans These regenerate the cornea ○ Growth factors Promote epithelialization/healing/collagen regeneration Epidermal growth factor ECF, transforming growth factor beta TGFβ, fibroblast growth factor FGF, platelet-derived growth factor PDGF  It facilitates ○ Epithelial cell migration ○ Reinforces adhesion of basal epithelial cells ○ Promote epithelium differentiation ○ Prevents epithelial apoptosis (cell death) ○ Minimize pain (coverage) and neovascularization (b/c it is providing nutrients) ○ Is not considered a corneal transplant*** (boards ?) Amniotic membrane is a graft ○ PROKERA (FDA-approved cryopreserved amniotic membrane) In conjunction w/ corneal transplants Limbal stem cell deficiency Persistent corneal epithelial defect RCE SJS DES Infectious keratitis Filamentary keratitis Exposure keratitis Neurotrophic corneal diseases Bullous keratopathy Ulceration (superficial or deep) Post PRK haze Acute corneal burns Salzmann’s nodular degeneration Fornix or socket reconstruction  Keratoplasties Kerato (cornea) + plasso (to form) Abnormal corneal tissue is replaced by a healthy donor cornea Partial: lamellar anterior or posterior Full thickness: penetrating keratoplasty Indications ○ Optical: improve VA ○ Tectonic: restore or preserve ○ Therapeutic: remove tissue not responsive ○ Cosmetic: appearance Donor tissue  ○ Eye banks ○ Eye removed within 12-24 hr of death ○ Endothelial cell count- 2,000-2,200 cells/mm^2 ○ Infant corneas ( (-8) D  ○ Fit GPs or reverse geometry lenses after 8-12 w ○ Refractive surgery enhancement could be considered ○ Loss of vision is rare Glare ○ Worse glare is expected in Small ablation zones Large pupils Monovision correction Higher refractive errors Dry eye ○ MORE COMMON SE of LASIK surgery ○ 33% of all surgeries ○ Corneal nerves are severed during the procedure Decreased corneal sensitivity Decreased neural feedback to the lacrimal gland Often improves within 1-2 months Diffuse Lamellar Keratitis (DLK or Sands of the Sahara) ○ Rare ○ Inflammatory, non-infectious reaction in the lamellar interface (b/w flap and stroma) ○ Fine, granular, sand-like infiltrates ○ 2-3 days after surgery ○ Unknown etiology Believed response to toxins Blade debris or microkeratome oil Less common in disposable microkeratomes ○ ○ Symptoms Asymptomatic Photophobia Blurred vision FBS Pain Vision loss from corneal scarring if not related ○ Treatment Topical steroids  If not responding, irrigation beneath the flap Central Toxic Keratopathy (CTK) ○ Rare 0.2-0.7% ○ Controversial pathogenesis Meibomian gland secretion Marking ink Talc from glove are the reported inciting factors ○ Symptoms Pain, redness, photophobia, glare and halo b/w 2-6 days ○ Signs Central cornea opacification, hyperopic shift (3-6 D) and corneal thinning ○ DDx microbial keratitis ○ Tx none— spontaneous regression ○ Steroids are not indicated is a non-inflammatory condition ○ Epithelial in growth ○ Rare ○ Less 3% of surgical cases ○ Most common complication after LASIK enhancement*** ○ Late postoperative LASIK complication ○ Most commonly at one month post-op ○ Faint gray or white line, milky deposits within 2 mm of the flap edge interface ○ Migration of epithelial cells beneath the flap; mainly in central vision ○ Asymptomatic ○ Not related trends to progress ○ Antibiotics and steroid topical treatment ○ Monitor if increase surgical procedure by flipping the flap and scraping  ○ ○ ○ Corneal haze ○ Prevalence of long-term haze w/ LASIK is 0.1% w/ PRK 1% in refractive errors below 6 D more common in PRK ○ Risk increase w/ higher RE ○ Normal haze is present after several weeks in PRK  ○ Retreatment Criteria for Enhancement Earliest time 3 months 6 months is preferred Criteria ○ Astigmatism > 0.75 D w/ symptoms ○ RE > or = 0.75 D from target in unhappy patients ○ Uncorrected VA of 20/30 or worse in unhappy patients Long-term management IOP: falsely low due to thin corneas Gonioscopy and retinal evaluation still necessary in high hyperopia or high myopia, respectively Wear eye protection during contact sports Sunglasses to avoid UV radiation RE surgery success 20/40 VA or better 90-99% of the patients achieve this level in low RE 75% achieve 20/25 or better Conductive Keratoplasty (CK) Treat presbyopia, low hyperopia, residual astigmatism or previous surgery Uses radio frequency energy to shrink the collagen fibers in the peripheral corneal stroma Regression is expected after 2-3 years Surgery can be repeated Treatment range: +0.75 D to +3.00 D with less than 0.75 D of astigmatism Intrastromal Corneal Rings (Intacs) PMMA rings inserted in the peripheral stroma to flatten the cornea— shortens cornea arc length Rings can be removed or exchanged Treatment for keratoconus Treatment range: -0.75 D to -3.00 D ○ not to treat hyperopia**  Clear lens extraction THIN corneas that want RE Cataract surgery without cataract IOL is calculated to reduce refractive error No residual accommodation remains unless a multi focal IOL is used Large treatment range Commonly done in myopia Phakic IOL IOL implantation in phakic eye IOL selected to correct refractive errors with lens D IOL is angle supported, iris supported, or sulcus supported Requires peripheral iridotomy Treat larger range of refractive errors IOL is removable Preserves accommodation Common complications: chronic uveitis, glaucoma secondary to this procedure Astigmatic keratotomy (AK) Corneal incisions made with diamond blade to relax cornea in the steepest meridians  Wave-front guided, custom corneal surgery Reduces higher order aberrations, more complications and not as done anymore Can be done w/ LASIK and PRK