Have questions?

PACK means “Photoactivated chromophore for infectious keratitis”-CXL. The term was defined by our Chief Scientific Officer Prof. Farhad Hafezi and others at the 2013 CXL Experts Meeting in Zurich, Switzerland, see https://pubmed.ncbi.nlm.nih.gov/24983827/

Because the infiltrate/ulcer breaks down the epithelium over the infection, all that needs to be done is to remove debris with a dry sponge, if necessary.

The entire cornea should be instilled with riboflavin and irradiated. This is for two reasons:

 1) The riboflavin induces the killing effect, but it also acts as a shield from the UV light, by absorbing it. The riboflavin in the periphery of the healthy cornea is protecting the corneal endothelium from too much UV irradiation, and

 2) The ulcer is bigger than the visible portion of it (compare it to the top of an iceberg). By irradiating the entire cornea, we ensure that the “invisible” parts of the ulcer are treated, too.

Bacteria, including Staphylococcus aureus, both MSSA and MRSA (antibiotic (Methicillin)-sensitive and antibiotic-resistant), Pseudomonas aeruginosa, and Staphylococcus epidermidis: efficacy 80–99%.

Fungi, including Fusarium and Candida albicans: efficacy 60–70%.

The experimental work required to demonstrate this has not been completed. As a correlate Solar disinfection (SODIS) is a similar technique to PACK-CXL. In SODIS, water is disinfected using sunlight (energy) and riboflavin. SODIS can kill Herpes simplex virus and acanthamoeba, but the overall total energy is much higher than what we currently use in the cornea.

It certainly helps to kill additional microorganisms and it also increases the resistance of the tissue to digestion. The latter should help keeping the resulting scar smaller than with an antimicrobial treatment alone. More clinical studies are needed to answer this clinical question.

No limitations are known.

Daily consultations, continue with standard antimicrobial treatment, treating the open corneal surface.

There currently is too little data to give a clear answer. However, the PACK-CXL energy settings are the same as in classic CXL for keratoconus, and here, we know that a repeated treatment is possible without harming the eye.

PACK-CXL is an addition to classic antibiotic treatment. It should be used as early as possible, and it should help to accelerate the time to healing. In Particular, PACK-CXL increases the stromal resistance to digestion. This is something an antibiotic does not do, and this might help keeping the final scar minimal.

We currently recommend using PACK-CXL in early infection. In early infection, the cornea usually still is thick enough for CXL, even at the area of infection.

In cases where an advanced ulcer is treated, the aim, also in classic treatment, usually is to “calm” the surface and end up in a quiescent scar. Usually, the underlying endothelium is not functional anymore.

If PACK-CXL is used in these cases, the irradiation might indeed harm the part of the endothelium over the thinnest part of the eye, but it will also kill additional pathogen and help preserve the eye as a structure.

A risk/benefit analysis must be made by the doctor: even when using antibiotics only, a quiescent scar would the best outcome possible. Under these circumstances, the doctor has to decide whether he/she wants to use PACK-CXL to further increase chances of calming the situation.