ABSTRACT
OBJECTIVE: The purpose of this study was to evaluate the safety and efficacy of transepithelial corneal collagen cross linking (TE-CXL) with modified riboflavin and accelerated UVA irradiance in thin corneas with pachymetry less than 400 microns at thinnest point, untreatable by epithelium off corneal collagen cross linking (CXL) in adult Pakistani population with progressive keratoconus. METHODS: This quasi experimental study included twenty six eyes of 26 patients with progressive keratoconus who underwent accelerated transepithelial CXL in Armed forced institute of ophthalmology with 12 months follow up. Modified riboflavin, ParaCel ((riboflavin 0.25%, Benzalkonium chloride, EDTA, Trometamol, hydroxypropyl methylcellulose) and vibeX Xtra (riboflavin 0.25%) (Avedro, USA)) were applied to cornea in two stages. Uncorrected and Corrected Distant Visual Acuities (UDVA, CDVA), spherical equivalent (SE), astigmatism, pachymetry at thinnest point (Pachy thin), apex keratometry (Kmax), simulated and steep keratometry (Sim K, steep K) were measured at baseline and at 3, 6 and 12 months post operatively. The cornea was then exposed to accelerated UVA irradiance of 9mW/cm2 for 10 min (total dose 30 mW/cm2). RESULTS: The mean age of the patient was 24.54±5.16 years. UDVA, CDVA, SE, astigmatism significantly improved at all postoperative test points (p=0.000, 0.004, 0.000, 0.004 respectively). Kmax and pachy thin were significantly reduced over baseline at 1 year (p=0.000, 0.004 respectively). Topographic indices Sim K and steep K did not show significant changes. No intra or post-operative complications were reported. CONCLUSION: Transepithelial accelerated CXL with modified riboflavin is a safe and effective procedure which halt disease progression in thin corneas with progressive keratoconus.
ABSTRACT
PURPOSE: The purpose of this study is to compare the safety and efficacy of transepithelial corneal crosslinking (CXL) with epithelium-off crosslinking (epithelium-off CXL) in the treatment of progressive keratoconus in adult Pakistani population. MATERIALS AND METHODS: Sixty-four eyes of 64 consecutive patients of progressive keratoconus were included in this quasi-experimental study. Thirty-two eyes received transepithelial CXL with Peschke TE (0.25% riboflavin (Vitamin B2), 1.2% hydroxypropyl methylcellulose (HPMC), 0.01% benzalkonium chloride) and 32 eyes received epithelium-off CXL with Peschke M (0.1% riboflavin (Vitamin B2) 0.1%, HPMC 1.1%.) The cornea was then exposed to ultraviolet A light at an irradiance of 3 mW/cm2 for 30 min. The primary outcome measure, clinical stabilization of keratoconus was defined as an increase of no more than 1D in Kmax at 1 year. Other parameters evaluated at baseline and 3, 6, 12, and 18 months postoperatively were uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), spherical equivalent (SE), astigmatism (Ast), simulated keratometry, steep keratmetry (steep K), and corneal thickness at thinnest point (pachy thin). RESULTS: Both epithelium-off CXL and transepithelial CXL groups showed a significant reduction in Kmax, steep K, simulated K, corneal pachymetry at all test points (P < 0.05) with significantly greater reductions achieved in epithelium-off CXL group at 18 months follow-up. The mean UDVA, CDVA, SE, Ast significantly improved in both groups (P < 0.05). The mean postoperative UDVA and CDVA between the groups were not significant at 12 months (P = 0.650, 0.018, respectively). Clinical stabilization was achieved in 94% of eyes in epithelium-off CXL and 75% of eyes in transepithelial CXL. In epithelium-off CXL, three eyes exhibited stromal haze resolved by corticosteroid treatment. No complication was documented in transepithelial CXL group. CONCLUSION: Transepithelial CXL is not recommended to be replaced completely by standard epithelium-off CXL due to continued ectatic progression in 25% of cases. However, thin corneas, unfit for standard epithelium-off CXL, can benefit from transepithelial CXL.