PACK-CXL is the application of cross-linking for the treatment of corneal infections. Based on extensive experimental data and an important clinical background, we do know that ultraviolet light has teratogenic effects on different germs, which makes it capable of sterilizing superficial infections. Ultraviolet light has been extensively used to disinfect cosmetic and surgical gadgets, aiming to avoid infections. The therapeutic use of ultraviolet light is the background of PACK-CXL. Dr. Hafezi and colleagues have shown preliminary clinical data that has demonstrated that corneal infections, when treated early and not very aggressively, can be sterilized by one or several sessions of ultraviolet light provided at the slit lamp with a special device designed by them. The usefulness of the procedure is demonstrated, and its main advantages are simplicity, cost-effectiveness and ease of application. The treatment performed at the slit lamp is controlled by the surgeon, and it can be repeated according to clinical decisions.
Our research department and I already have more than 6 years of experience in the use of collagen cross-linking for the treatment of corneal infections. Based on the Dresden protocol, we started using it in corneal keratitis resistant to all medical therapies, particularly of fungal origin. Our outcomes have been good and have demonstrated the usefulness of CXL in the treatment of this type of severe, untreatable infection, as a coadjuvant to other therapies. Our experience in Fusarium keratitis has been outstanding, and we were able to save cases that were otherwise impossible to solve without a corneal graft, which in acute uncontrollable infections is usually a failed procedure. We have learned that CXL can be repeated twice and even up to four times to sterilize a case. Not only that, CXL decreased from the very beginning pain and inflammation, consolidated the cornea from melting and prevented corneal perforation. We did, based on our results, a meta-analysis review in which it was clear that the evidence in favor of CXL in the treatment of corneal infections was well sustained by evidence.
Our preferred practice at this moment for infectious keratitis is to start with fourth-generation quinolones in case we suspect a bacterial infection, and in cases that we consider that we are dealing with a fungi, microbacteria or Acanthamoeba, from the very beginning we use CXL with the Dresden protocol. We eliminate the epithelium around the ulcer, and we treat during the time of the Dresden protocol, the cornea impregnating in the same way as we do in keratoconus. Corneal thickness behaves in a different way than in keratoconus because we are dealing with an opaque area of the cornea, and even in those cases in which there is a thin cornea for cross-linking, we have never suffered a corneal decompensation because the corneal abscess blocks the pass of ultraviolet light. We know that from the beginning the case will improve, but we also know that the treatment should be repeated several times, 1 week apart. At the same time, we are providing topical therapy to the suspected infection.
So far, PACK-CXL may be applicable and has an indication in early corneal infections, according to recent evidence, particularly when located superficially. Its application should be ideal in bacterial keratitis cases coming from contact lens use, corneal trauma including contamination from the agricultural environment and postoperative corneal graft surgery.
The main pitfalls of PACK-CXL are lack of demonstrated usefulness in well-established bacterial keratitis and doubtful effectiveness in deeply located corneal infiltrates because the superficial layers will prevent the action of the ultraviolet light. It also may not be effective in cases in which the corneal opacity is happening in the environment of the suspected or confirmed corneal infection.
What are the future perspectives of collagen cross-linking applied to the treatment of corneal infections? A straightforward, cheap device attached to the slit lamp seems to be ideal for medical use. Its ease of use and accessibility will be ideal for those areas of the world in which corneal infections are frequent. Not only that, it may prevent the use of topical medications such as fortified antibiotics, which are toxic for the ocular surface and particularly the corneal epithelium. Based on the evidence published by us and others, and the recent information provided by the work of Hafezi, CXL should be considered as an option for any type of initial corneal infection, particularly, in our opinion, for those in which a resistance to antibiotics is expected or a doubtful bacterial origin is anticipated.
PACK-CXL is a useful technique that deserves further attention by clinical and surgical ophthalmologists.
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- For more information:
- Jorge L. Alió, MD, PhD, is an OSN Europe Edition Board Member. He can be reached at Vissum Corporation, Avenida de Denia, s/n, 03016 Alicante, Spain; email: firstname.lastname@example.org.
Disclosure: Alió reports no relevant financial disclosures.