Aim of the Study: Compare the corneal demarcation line (DL) depth after corneal collagen cross-linking (CXL) with subtotal versus customized corneal epithelium debridement using anterior segment optical coherence tomography (AS-OCT).
Design: Prospective case-control study.
Materials and Methods: The study enrolled 18 patients with bilateral progressive keratoconus. Both eyes treated by CXL using a 3 mW/cm2 / 30 minutes setting. One eye with subtotal epithelial debridement (about 9 mm diameter) and the contralateral eye with customized debridement (approximately 1 mm single horizontal central scratch). One month postoperatively, patients had AS-OCT imaging to detect and measure the depth of DL.
Results: Patients’ age mean was 25.17 years +/- 4.81 SD. Epithelial healing completed within 3-7 days in the conventional treatment group and demarcation line was evident in 16 eyes (89%) with a mean depth of 290.31 μm while in the customized debridement group, the epithelial healing lasted less than 24 hours and DL was detectable in 10 patients (55.5 %) with a mean DL depth of 221 μm with a statistically significant difference (p<0.05). Subjective postoperative pain graded as “moderate to severe” in about 77% of eyes underwent 9 mm epi-off CXL compared with 55% of those with customized debridement group.
Conclusions: Although the DL if found in the majority cases, but the shallow location in customized corneal debridement cases questioned the efficacy of this technique despite the quick re-epithelialization and less postoperative pain that accompanied it.
Keratoconus; Demarcation line; Corneal Collagen Cross-Linking; Anterior Segment Optical Coherence Tomography
Keratoconus is a bilateral, usually asymmetrical noninflammatory a progressive ectatic corneal disorder that can cause a significant visual morbidly. It affects the central and paracentral cornea and the cornea progressively becomes conical in shape and it typically presents in puberty and usually associated with progressive corneal thinning and irregular myopic astigmatism that may mandate transplantation .
Estimated incidence of keratoconus ranged from 1.3 to 22.3 cases/100000 and prevalence from 0.4 to 86 cases/100000 [2,3], this wide range of incidence is thought to be governed by a variety of genetic and environmental factors [4-6].
Keratoconus is a common eye problem in Middle East area, including the current study locality where atopy and vernal keratoconjunctivitis is endemic [7-10].
Since the introduction of collagen cross-linking using ultraviolet radiation type A (UV-A) and riboflavin as a treatment option to limit the progressive keratoconus by Spoerl and Seiler at the University of Dresden , it gained worldwide popularity as a novel conservative strategy to halt or decrease the progression of various corneal ectasia including keratoconus, pellucid marginal degeneration, post-LASIK ectasia and keratoglobus [12-14]. This technique reported flattening the cornea stabilize the progression of irregular astigmatism .