LAUSR

In 1997, Wollensak and Spoerl introduced collagen crosslinking with riboflavin with the Standard Corneal Collagen Crosslinkage (SCXL) for the management of progressive Keratoconus (KC).[1] The photochemical process induces additional crosslinks between the collagen fibers, which is dependent upon the applied radiant exposure of ultraviolet (UV) light.[1] The efficacy and long-term safety of S-CXL in adults and children have already been established with many studies in the literature.[2] The concept of accelerated CXL (A-CXL) was introduced by Schumacher et al.[3] to reduce the treatment duration, improve the patient’s comfort, and reduce the risk of microbial keratitis. Later, many settings have been made based on the Bunsen–Roscoe law of reciprocity.[4] The various settings for A-CXL are at 9 mW/cm2 for 10 min, 30 mW/cm2 for 3 min, 18 mW/cm2 for 5 min, and 45 mW/cm2 for 2 min and all deliver a constant energy dose of 5.4 J/cm2.[5] A-CXL also allows thinner corneas to be crosslinked with greater precision.[6] The A-CXL protocols are slowly replacing the standardized protocols in ophthalmic practice. Previously, many authors have stated that the A-CXL procedure is less efficient in stabilizing KC than S-CXL due to the reduced duration of the procedure and decreased exposure to atmospheric oxygen levels for the photochemical reaction.[5] So, it is imperative to know the long-term safety and efficacy of A-CXL protocols and understand the predictability of the procedure to stop the progression of the disease. With interest, the authors conducted the present study, which highlights the 5-year results of visual tomographic outcomes and identifies the preoperative risk factors that are predictive of these outcomes with A-CXL (18 mW/cm2 for 5 min).[7] After the publication of the first article by Tomita et al.[8] on comparing S-CXL versus A-CXL, many clinical trials have been conducted to study the results of different types of A-CXL protocols. Shetty et al.[9] made a prospective comparison of different A-CXL protocols and found that A-CXL with 10 min produced significant topographical improvement compared to S-CXL. The authors also highlighted that the procedure’s efficiency decreases with increase in the amount of energy delivered. Very few authors have studied A-CXL outcomes with 18 mW/cm2 for 5 min. Hashemi et al.[10] conducted a prospective study and compared the long-term (18 months) outcomes of A-CXL (for 5 min) with S-CXL and observed that although visual acuity and safety profile are comparable, corneal flattening is better with S-CXL. The present study has added the following facts to the literature on 5-min A-CXL: 1) It has established long-term efficacy in causing significant flattening of mean and maximum K in advanced keratoconus (>58 D) compared to mild to moderate cases, without KC progression throughout the 5-year follow-up. However, Vinciguerra et al. reported that S CXL is ineffective in preventing progression in patients with Kmax value >58 D and reported a 7.4% failure rate at 13 years of follow up.[11] In addition, Nicula et al. recently reported a 3.84% failure rate at 7 years of follow up with A CXL 10 min, but all patients had allergic conjunctivitis.[5] 2) Long-term stability of Uncorrected distance visual acuity (UDVA), Corrected distance visual acuity (CDVA), manifest cylinder, CCT, steep K, and posterior elevation at the apex, throughout the 5 years 3) The stability of endothelial counts was an interesting aspect to note, since 14 patients had advanced disease with K >58 D, which indirectly predicts the safety of high-intensity UV radiation used in A-CXL. 4) CCT and Corneal thickness at the thinnest point (TCT) levels were decreased approximately by 12 and 14 μm, respectively, which is less than S-CXL. 5) The complications of microbial keratitis and endothelial decompensation were not observed throughout the 5 years of follow-up. 6) Many studies have established that the Kmax is the most commonly used parameter to determine KC progression. This study has found a long term association of high preoperative Kmax values and success of the treatment with A CXL, similar to the study by Kirgiz et al.[12]