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| 1. Which statement about keratoconus is true? |
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A.
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It affects every one in 1,500 people. |
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B.
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Patients with keratoconus have decreased pepsin digestion. |
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C.
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Current "conventional" treatment options include rigid gas permeable lenses, penetrating keratoplasty and photorefractive keratectomy (PRK). |
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D.
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Patients with keratoconus have a reduced number of corneal collagen cross-links. |
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| 2. Which statement about corneal collagen cross-linking (CXL) is TRUE? |
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A.
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It involves debridement of the central 3mm to 4mm of the corne |
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B.
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It increases corneal rigidity by inducing additional cross-links within or between collagen fibers. |
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C.
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It causes a 70% to 300% decrease in corneal rigidity. |
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D.
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The first application of CXL was used to treat microbial keratitis. |
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| 3. Which statement about the CXL procedure is FALSE? |
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A.
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Riboflavin 0.1% permeates the cornea after UVA irradiation. |
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B.
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Riboflavin is reapplied every five minutes during the irradiation. |
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C.
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The irradiation process takes approximately 30 minutes. |
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D.
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An antibiotic ointment is used after CXL until corneal reepithelization is achieve |
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| 4. Which statement is FALSE? |
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A.
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UVA radiation causes keratocyte and corneal endothelial death. |
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B.
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CXL treatment should be restricted to the anterior 250µm to 350µm of the stroma. |
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C.
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Sixty-five percent to 70% of UVA radiation is absorbed in the posterior 200µm of the cornea. |
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D.
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The deeper structures of the cornea, crystalline lens and retina are spared by CXL. |
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| 5. CXL should not be performed in patients whose corneas are thinner than: |
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A.
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400µm. |
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B.
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425µm. |
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C.
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450µm. |
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D.
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500µm. |
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| 6. Which description of the CXL procedure is TRUE? |
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A.
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CXL facilitates covalent bond formations between collagen fibers and increases collagen fiber diameter. |
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B.
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After CXL, patients with keratoconus are more susceptible to pepsin digestion. |
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C.
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CXL stiffens the anterior 300µm microns of the cornea. |
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D.
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CXL often causes extensive collateral damage to unexposed limbal areas. |
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| 7. What is NOT a corneal change caused by CXL? |
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A.
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Superficial nerve loss. |
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B.
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Cellular modification. |
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C.
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Decreased edema. |
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D.
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Isolated endothelial damage. |
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| 8. What is one early effect of CXL on the cornea? |
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A.
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There is virtually no keratocyte apoptosis of the strom |
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B.
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The nerve plexus is well defined. |
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C.
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There is decreased reflectivity of the extracellular matrix. |
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D.
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There is increased keratocyte density. |
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| 9. Which statement is FALSE? |
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A.
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There is no damage to the limbal cells during CXL. |
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B.
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Keratocyte apoptosis occurs up to 300µm deep in the stroma. |
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C.
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The epithelium regenerates completely four days after CXL. |
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D.
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The mid- and anterior stroma keratocytes completely repopulate after one year. |
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| 10. What is the current CXL failure rate? |
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A.
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7.6%. |
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B.
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10.5%. |
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C.
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13.8%. |
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D.
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18.3%. |
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| 11. What is a possible risk factor for CXL failure? |
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A.
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Preoperative best-corrected spectacle visual acuity better than 20/25. |
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B.
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Preoperative maximum keratometry greater than 48.00D. |
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C.
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Corneal scarring. |
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D.
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A history of corneal infiltrates. |
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| 12. What is a common complication following CXL? |
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A.
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Bacterial keratitis. |
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B.
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Acanthamoeba keratitis. |
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C.
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Corneal infiltrates. |
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D.
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All of the above. |
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| 13. What is true of stromal haze secondary to CXL? |
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A.
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It often self-resolves within one month. |
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B.
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It is associated with a loss of keratocytes. |
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C.
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It is similar to the haze found after PRK. |
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D.
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Thicker corneas have a higher risk of haze development. |
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| 14. What is NOT a common complication associated with CXL? |
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A.
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Loss of visual acuity. |
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B.
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Stromal haze. |
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C.
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Decreased IOP. |
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D.
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Acanthamoeba keratitis. |
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| 15. Which statement about IOP and CXL is FALSE? |
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A.
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Increased IOP secondary to CXL is permanent. |
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B.
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Goldmann applannation tonometry may not be the best device to measure IOP in patients who have undergone CXL. |
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C.
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On average, IOP increases by 4mm Hg following CXL. |
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D.
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On average, IOP decreases by 2mm Hg following CXL. |
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| 16. What is true of CXL without epithelial debridement (C3R)? |
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A.
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C3R may improve ocular biomechanical function. |
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B.
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C3R may reduce the risk of postoperative infection. |
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C.
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C3R improves riboflavin uptake. |
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D.
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C3R does not cause postoperative pain, edema or superficial nerve loss. |
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| 17. What procedure is NOT a current modification of CXL? |
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A.
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Hypo-osmolar riboflavin. |
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B.
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Hyper-saturation of riboflavin. |
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C.
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Short-chain aliphatic ß-nitro alcohols. |
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D.
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Flash-linking. |
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| 18. What percentage of patients who underwent CXL reported at least one line of visual acuity improvement at three-year follow-up? |
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A.
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25%. |
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B.
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38%. |
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C.
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46%. |
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D.
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58%. |
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| 19. Overall, what does the CXL procedure achieve? |
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A.
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Corneal flattening. |
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B.
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Reduction in spherical abberation. |
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C.
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Reduction in astigmatism. |
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D.
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All of the above. |
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| 20. What is NOT a potential treatment application for CXL? |
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A.
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Corneal melts. |
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B.
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Keratoconus. |
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C.
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Post-LASIK keractasia. |
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D.
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Infectious herpes simplex. |
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