Chapter 18 Flashcards
What topical medication is commonly used to reduce the risk of subepithelial corneal haze after photorefractive keratectomy (PRK)?
Corticosteroid.
In PhotoRefractive Keratectomy (PRK), the corneal epithelium is mechanically removed, and the anterior surface of the stoma is ablated by the excimer laser. There is great risk of subepithelial corneal haze due to growth of scar tissue. Corticosteroids (SAIDs) inhibit scar forming cells.
What is the intended effect of a refractive surgery on corneal curvature for hyperopia correction?
Steepen the cornea.
Hyperopic patients can benefit from surgeries that steepen the cornea and increase refractive power, such as Conductive Keratoplasty
What finding on corneal pachymetry is a contraindication to Laser in Situ Keratomileusis?
Thin Cornea.
Thin corneas are greater risk for ectasia after LASIK. Thinning with protrusion (Keratoconus) may yield erratic results after surgery.
Intrastromal corneal ring segments are most commonly used for what condition?
Early Keratoconus.
Intrastromal Corneal Ring Segments (ICRS or Intacs prescription inserts) we’re originally used to treat low degree of myopia but are now more commonly used in low degrees of Keratoconus and ectasia after LASIK. Segments are placed in the midperipheral cornea to flatten the curvature of the central cornea.
What complication is more likely to occur after Photorefractive Keratectomy (PRK) than Laser in Situ Keratomileusis (LASIK)?
Subepithelial corneal haze.
In PRK there is greater risk of growth of scar tissue causing haze. In LASIK corneal strength under the created flap can be reduced and may result in corneal ectasia
In absence of accommodation, where does the hyperopic eye focus images?
Behind the retina.
However for younger patients who can still accommodate, enough additional plus power may be produced to focus on the retina. A cycloplegic refraction limited accommodation and allows for full correction
What type of optical aberrations cannot be detected by conventional refraction techniques?
Higher-order.
Aberrations such as spherical aberration, coma configuration, and other forms of irregular astigmatism can be measured with forms of wavefront analysis called Aberrometry.
What corneal surgery is reversible?
Intrastromal corneal ring segments. Limited in use: such as low degree myopia, early Keratoconus, and ectasia after LASIK, the main benefit of ICRS is that they are removable.
What kind of astigmatism can’t be corrected with astigmatic keratotomy?
Irregular.
Astigmatic Keratotomy (AK) employs transverse incisions to manipulate the meridians but is limited to low-grade, regular astigmatism.
What is a term for wavefront error measurement?
Aberrometry.
Using lasers and wavefront deformation measuring devices, higher-order distortions and phakic IOL correction is increasing in accuracy
