13- Corneal Cross Linking

Flashcards on Corneal Cross Linking

What is keratoconus?

Progressive, bilateral, asymmetric ectatic disease, progressive corneal thinning and protrusion of the cornea leading to irregular astigmatism that eventually causes visual deterioration.

What is the incidence of keratoconus?

1 in 2000 (probably underestimated due to lack of instrumentation)

Name the risk factors of keratoconus:

All of the above

Name the risk factors of keratoconus:

All of the above

What ocular factor can be a risk factor for keratoconus?

Ocular allergy causes more rubbing.

What ethnicity is a risk factor for keratoconus?

Patients of middle eastern descent are more at risk.

What is Vogt striae?

Stress lines in deep stroma and Descemet's membrane that can disappear upon application of mild pressure to the lower eyelid.

What layer of cornea does Vogt striae show?

Deep stroma and Descemet's membrane.

What is Rizzuti sign?

Sharply focused bean of light near nasal limbus while shining a light at temporal side that shows up in advanced keratoconus.

What is Fleishers ring?

Iron deposit on epithelium identified with cobalt blue filter – classic sign of keratoconus.

What metal is deposited in the cornea in a Keratoconic eye?

Iron.

What is Munson's sign?

Advanced keratoconus sign & tent like appearance of lower eyelid when pt is asked to look down.

What is considered progression of keratoconus based on global consensus?

All of the above

Which of the following is not used in FDA approved protocol of cross linking?

370 nm (UV B).

Who is eligible for a crosslinking treatment?

Young patient under 30, with a BCVA worse than 20/20.

What is the treatment or medication used after surgery?

Topical steroid to delay epithelial growth for 1-2 months.

Which of the following is not a contraindication of crosslinking?

Smoking young patients.

What radiation is used for crosslinking?

370 nm UVA radiation.

How does the crosslinking procedure work?

Occurs between proteoglycans of ECM and amino terminal of collagen & creates new covalent links between collagen fibers of stroma.

What does extreme corneal thinning from keratoconus lead to?

Rupture in Bowman’s which produces subepithelial or anterior stromal scars.

What is seen with the slit lamp when keratoconus is present?

Increased endothelial reflection.

What is Charlouex’s oil droplet reflex?

Total internal reflection in conical cornea, dark shadow around mid periphery which separates central bright red fundus reflex from red reflex in periphery.

What is indicative of keratoconus in regards to corneal nerves?

Excessive corneal nerve endings – different from DM which results in decrease.

What is acute hydrops?

Rupture of Descemet’s membrane resulting in sudden unilateral redness and painful loss of vision and sudden imbibition (water uptake) of aqueous humor into the cornea leading to stroma edema.

What happens if acute hydrops occur to the patient?

Cannot examine patient further for crosslinking, patient needs surgery for corneal transplant.

Which of the following is not a type of cones in keratoconus?

Diamond cone: edges prevent light scattering with CL.

What happens to patients who wear contact lenses and have keratoconus?

38% increase of scarring.

What is cross linking?

Term derived from the assumption of creating new covalent chemical bonds between stromal collagen side chains and the proteoglycans of the extracellular matrix.

What might occur in the eye naturally in keratoconus?

Cornea becomes more rigid by glucose from AH along with UV exposure.

Who is the ideal candidate for crosslinking?

All of the above

When can you not perform an OCT on a patient with keratoconus?

If acute hydrops is present.

What radiation is used for crosslinking?

UV A radiation.

What might a patient expect post operative management of CXL?

Delayed epithelial healing & corneal haze (up to 90% will have some degree of it, typically resolves 6-12 months).

What might happen due to a delayed epithelial healing by steroid after CXL?

Increase risk of keratitis.

What are contraindications for keratoconus CXL?

ME.

What is the Avedro KXL?

Accelerated CXL – 3 minutes exposure.

What is the difference between the Dresden Protocol CXL FDA approved and epithlium on crosslinking?

The efficacy of epithelium on CXL remains inferior to the epithelium off approach, although it is significantly safer.