Conj/Cornea/Refractive Surgery Flashcards
Question
Neurotrophic keratopathy is a rare degenerative corneal disease that is caused by impairment of which of the following nerves?
Cranial nerve V Cranial nerve IV Cranial nerve VI Cranial nerve VII Cranial nerve II Cranial nerve III
Cranial nerve V
Explanation
Neurotrophic keratopathy is a rare degenerative corneal disease that is caused by impairment of trigeminal innervation. This subsequently leads to corneal epithelial breakdown and impaired healing processes which can eventually result in corneal ulceration, melting, and even perforation. The hallmark sign of neurotrophic keratitis is decreased corneal sensitivity. Potential etiologies for deterioration of the trigeminal nerve include acquired damage to the trigeminal ganglion, stroke, aneurysm, or tumor. Systemic diseases and congenital disorders such as diabetes, multiple sclerosis, and Goldenhar syndrome are also associated with neurotrophic keratopathy.
Question
Which of the following BEST describes the etiology of marginal keratitis?
Type IV hypersensitivity
Type I hypersensitivity
Type III hypersensitivity
Type II hypersensitivity
Type IV hypersensitivity
Explanation
Marginal keratitis occurs as a result of a type IV hypersensitivity reaction to bacterial antigens in the presences of Staphylococcal blepharitis. Patients will typically present with red, irritated eyelid margins that are often thickened and show prominent blood vessels. Slit lamp examination will reveal peripheral corneal infiltrates (due to a migration and influx of white blood cells) that can be either unilateral or bilateral and are found near the limbal area. These peripheral infiltrates are also often accompanied by sectoral conjunctival injection.
Question
Which of the following instructions is NOT typically part of the post-operative education for patients undergoing LASIK refractive surgery?
No excessive exercising for 1 week
Sleep with protective shields for 1 week
No eye makeup for 1 week
No swimming of any kind in hot tubs, swimming pools, lakes, ocean, etc. for 1 week
No computer work for 1 week
No computer work for 1 week
Explanation
Patients undergoing LASIK refractive surgery should be educated on the following precautions:
- No eye rubbing
- Eye shields should be worn at night while sleeping for 1 week
- Swimming in ocean, lakes, rivers, hot tubs, swimming pools, etc. should be avoided for at least 1 week
- No excessive working out for 1 week (especially those with head below the heart or involving Valsalva maneuver)
- Eye makeup should be avoided for 1 week
- Patients can read, go on the computer, watch TV, etc., but excessive use may cause dryness, so it is advised to use artificial tears
Question
Which of the following statements is TRUE in regard to the laser (or lasers) used during the SMILE refractive surgery procedure?
A femtosecond laser is used to create the corneal incision and stromal lenticule
An excimer laser is used to create the corneal incision and stromal lenticule
A femtosecond laser is used to create the corneal incision, and an excimer laser is used to create the stromal lenticule
An excimer laser is used to create the corneal incision, and a femtosecond laser is used to create the stromal lenticule
A femtosecond laser is used to create the corneal incision and stromal lenticule
Explanation
SMILE is the newest laser vision correction procedure, approved by the FDA in 2016. SMILE stands for small incision lenticule extraction. Unlike PRK and LASIK, there is no use of an excimer laser during the SMILE procedure. Alternatively, the surgeon uses only a femtosecond laser to cut a small incision into the cornea through which a small piece of corneal tissue is removed (called a lenticule), which is also created by the femtosecond laser.
Question
What is the current FDA guideline for the minimum residual corneal stromal bed thickness for patients undergoing LASIK refractive surgery?
250 microns 350 microns 400 microns 300 microns 200 microns
250 microns
Explanation
The United States Food and Drug Administration (FDA) currently recommends that the calculated residual stromal bed for patients undergoing refractive surgery must be at least 250 microns thick. The stromal bed refers to the thickness of the remaining corneal tissue measured post-ablation from the treated surface to the endothelium. Studies have indicated that patients with residual stromal thickness less than 250 microns have a significantly higher risk of developing iatrogenic corneal keratectasia (although ectasia can occur in patients with post-operative residual stromal thickness of greater than 250 microns).
Question
Which of the following types of laser are used when creating the corneal flap during LASIK refractive surgery?
Cyclodiode laser
Excimer laser
Femtosecond laser
Nd:YAG laser
Femtosecond laser
Explanation
Femtosecond lasers are utilized for creating the corneal flap during LASIK surgery. Each pulse of the femtosecond laser generates free electrons and ionized molecules, which leads to the formation of microscopic gas bubbles into the corneal tissue at a specified depth. Multiple pulses are applied adjacent to each other to create a cleavage plane and, ultimately, the LASIK flap.
Once the flap is created and lifted, an excimer laser is used to reshape the cornea.
