Photochemical Keratodesmos Versus Sutures

Monday, October 20, 2014

The IOPL after PKD treatment was compared with that obtained using sutures. Two interrupted radial sutures of black monofilament 10-0 nylon (Ethilon suture; Ethicon, Piscataway, NJ) were used to close the keratome incision. The sutures were placed in a radial fashion at approximately 90% corneal depth. Preliminary experiments produced IOPLs of approximately 230 mm Hg. This pressure is similar for the incisions closed with PKD treatment. However, it was observed that the IOP was maintained even when there was leakage around the sutures. The leaks surrounding the sutures were reversible, whereas with PKD the damage was irreversible after the opening of the incision.


This study demonstrates the feasibility of using PKD treatment to close small incisions made in the cornea of rabbit eyes ex vivo. The results show that PKD produces a significant increase in the immediate IOPL of enucleated rabbit eyes after treatment of 3.5-mm corneal incisions.

The dose–response pattern observed for the PKD treatment, using RB as a photosensitizer, is not simple. Reduced IOPL and tissue shrinkage were observed consistently at the highest irradiance of 3.82 W/cm2 and occasionally at 2.55 W/cm2 for doses between 762 and 1524 J/cm2, which suggests contributions from both photochemical and photothermal processes. The ideal conditions to produce a clinically relevant IOPL with PKD are those that balance the shortest treatment time with the highest dose; the limitation is the thermal effects produced using high irradiances. In the cornea, photothermal effects may produce collagen contraction resulting in distortion of the patient’s vision. Therefore, higher irradiances that would allow a shorter treatment time are limited by thermal effects.

Other potential photosensitizers for PKD, chosen on the basis of suitable photochemistry, were investigated. PKD treatments using R-5-P and N-HPT produced increases in the IOPL. Relative efficiencies of the photosensitizers were evaluated by comparing the IOPLs produced by optically matched solutions of the photosensitizers at the same set of irradiances and doses. However, these comparisons do not take into account considerations such as the binding efficiency of the photosensitizers, which alters the dye concentration on the incision surface. All the photosensitizers generate singlet oxygen or reactive radicals that may be toxic to cells in the cornea. Future in vivo studies are needed to determine whether this effect is relevant and, if so, to evaluate possible protective agents. Our results using R-5-P are comparable with those found by Khadem et al.4–6 who used a photoactivated adhesive consisting of fibrinogen and R-5-P irradiated with argon ion laser light (488–514 nm) to close 5-mm penetrating central corneal incisions made in human cadaveric eyes. With this method of incision closure in a smaller sample size, a mean wound-bursting pressure of 154 mm Hg was found. The maximum mean IOPL observed in our study using R-5-P was 254 mm Hg. Our results suggest that the presence of fibrinogen is not necessary to obtain a good seal. Elimination of fibrinogen from the system removes the limitations imposed by using this protein, such as the limited tensile strength and the requirement that the fibrinogen be isolated from the patient to be treated, to avoid risk of infection from donor plasma.42 Other possible suture alternatives for use in ophthalmic surgery that have been investigated include chemical glues.1–3 Glues are limited by the requirement that they be nontoxic, noncarcinogenic, and biodegradable. In addition, glues do not generally provide a permanent closure; they are sloughed off within weeks of application.

Our results show that PKD treatment of small keratome incisions in rabbit cornea ex vivo produced IOPLs comparable with those incisions closed with sutures. The leaks associated with the sutures were reversible, but after the PKD-treated incision had been opened, the seal was completely lost. However, PKD treatment can easily and effectively be repeated on the previously treated incision.

PKD offers many potential advantages over the methods currently used to attach corneal tissue and close incisions in a variety of surgical procedures such as penetrating keratoplasty, laser in situ keratomileusis (LASIK), and cataract surgery and in the treatment of corneal lacerations. The sutures currently used in corneal transplants can induce postoperative astigmatism, neovascularization, and rejection of the donor cornea. Furthermore, loose or broken sutures can leave a patient vulnerable to microbial keratitis. The suturing procedures used are skill intensive and are mainly performed by corneal specialists. PKD offers a simple procedure to close wounds, spot seal LASIK flaps and attach donor cornea, reducing the operating and rehabilitation time.


The authors thank Norman Michaud and Thomas Flotte for collecting the confocal images and for useful discussion, Hans-Christian Luedemann and Dominic Bua for technical help, and Be´┐Żatrice M. Aveline for preparation of N-HPT.


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