Question 1. Which of the following statements regarding collagen cross-linking (CXL) is true?
A) CXL is a surgical procedure used to correct refractive errors.
B) CXL involves the use of a photosensitizing agent and ultraviolet-A (UVA) light.
C) CXL is primarily used to treat cataracts.
D) CXL is only effective in improving visual acuity in patients with myopia.
Answer : B
CXL was implemented in clinical practice in the late 1990s and has subsequently revolutionized the conservative treatment approach for progressive corneal ectasia. CXL employs riboflavin as a photosensitizer, which, upon exposure to longer wavelength UV-A, initiates biochemical processes within the corneal stroma, leading to the creation of covalent connections among the collagen molecules. This process of collagen crosslinking enhances the cornea’s tensile strength and stiffness, effectively impeding additional corneal thinning and ectasia development.
Reference: Vohra V, Tuteja S, Gurnani B, et al. Collagen Cross Linking for Keratoconus. [Updated 2023 Mar 16]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK562271/
Question 2. Indications for CXL include:
A) An increase of 1.00 diopter (D) or more in the steepest keratometry measurement in 12 months.
B) An increase of 1.00 D or more in the manifest cylinder in 12 months.
C) An increase of 0.50 D or more in the manifest refraction spherical equivalent in 12 months.
D) All of the above.
Answer: D
Commonly acknowledged indications for CXL include an increase of 1.00 diopter (D) or more in the steepest keratometry measurement, an increase of 1.00 D or more in the manifest cylinder, and an increase of 0.50 D or more in the manifest refraction spherical equivalent in 12 months.
Reference: Kato, N.; Masumoto, H.; Tanabe, M.; Sakai, C.; Negishi, K.; Torii, H.; Tabuchi, H.; Tsubota, K. Predicting Keratoconus Progression and Need for Corneal Crosslinking Using Deep Learning. J. Clin. Med. 2021, 10, 844. https://doi.org/ 10.3390/jcm1004084
Question 3. Risk factor for progression of keratoconus includes:
A) Young age
B) Eye rubbing
C) Preoperative Kmax more than 58D
D) All of the above
Answer D
Risk factor for progression of keratoconus includes young age, eye rubbing, allergic conjunctivitis, neurodermatitis, preoperative Kmax more than 58D at baseline and thinnest pachymetry.
Reference :
- Antoun J, Slim E, El Hachem R, Chelala E, Jabbour E, Cherfan G, Jarade EF. Rate of corneal collagen crosslinking redo in private practice: risk factors and safety. J Ophthalmol. 2015;2015:690961. doi: 10.1155/2015/690961. Epub 2015 Mar 19. PMID: 25874118; PMCID: PMC4383466.
- Sağlık, A., Özcan, G. & Uçakhan, Ö. Risk factors for progression following corneal collagen crosslinking in keratoconus. Int Ophthalmol 41, 3443–3449 (2021). https://doi.org/10.1007/s10792-021-01908-9
Question 4. Riboflavin 0.1% without Dextran on the cornea every 2 min for 10 min is used in
A) Conventional Corneal Collagen CXL (C-CXL)
B) Accelerated Corneal Collagen CXL (A-CXL)
C) Iontophoresis (I-CXL)
D) All of the above
Answer B
In conventional CXL, 0.1% riboflavin with 20% Dextran is applied on the cornea every minutes for 20 min followed by UV A irradiance of 3 mW/cm2 (5.4 J/cm2 surface dose) for 30 minutes. In accelerated CXL, 0.1% riboflavin without Dextran on the cornea every 2 min for 10 minutes followed by UV A irradiance of 30 mW/cm2 (5.4 J/cm2 surface dose) for 3 minutes. In iontophoresis, sticky passive electrode is applied on the forehead under the operative field and active electrode and, a suction ring to the open eye. Suction ring is filled with hypoosmolar 0.1% riboflavin without Dextran followed by UV A irradiance with 10 mW/cm2 (5.4 J/cm2 surface dose) for 9 min.
Reference:
Bouheraoua N, Jouve L, Borderie V, Laroche L. Three Different Protocols of Corneal Collagen Crosslinking in Keratoconus: Conventional, Accelerated and Iontophoresis. J Vis Exp. 2015 Nov 12;(105):53119. doi: 10.3791/53119. PMID: 26650390; PMCID: PMC4692706.