LASERS IN CORNEAL SURGERY

As femtosecond laser technology evolves, so do the ways in which the lasers are used in corneal surgery, according to George Kymionis MD, University of Crete, Heraklion, Crete, Greece. “Every day we discover a new application of this technology in corneal surgery. Femtosecond lasers significantly improve the efficacy and safety of corneal surgery,†he told the 16th ESCRS Winter Meeting. Since the earliest models came onto the market in 2001, the femtosecond laser has provided an improvement in the safety of LASIK procedures, he said. By enabling the more accurate creation of LASIK flaps, the laser reduces the complications that can arise when the flap is too thick or too thin, he noted. Over the years, the femtosecond laser has rapidly expanded its profile from being a high-tech microkeratome to becoming a precision scalpel, which can in many cases outperform the traditional tools used in corneal surgery, he said. Some of the surgical tasks for which it has proved its utility include the creation of tunnels in the corneal stroma for the placement of intracorneal ring segments, creating pockets for placement of intracorneal inlays, and performing astigmatic keratotomies, Dr Kymionis said.

Expertise enhanced

Dr Kymionis noted that femtosecond laser technology affords a level of accuracy that is in some cases unattainable by even the most experienced surgeon using conventional tools and manual techniques. The way it provides such accuracy is through the delivery of very high amounts of energy in very short pulses, he added. To illustrate his point he described several short cases where the femtosecond laser had achieved an accuracy far surpassing that which had previously been possible. One case was a patient undergoing implantation of intracorneal ring segments. He programmed the femtosecond laser to create tunnels for the ring segments at a depth of 400 microns. Postoperative anterior segment OCT showed that the tunnels were at a depth of 417 microns. “I don’t think even the best surgeon can achieve this kind of result with a mechanical device, and accuracy in the depth of INTACS implantation means better results.â€

Custom-fit keratoplasty

One of the most exciting uses of the femtosecond laser is in the creation of perfectly matching donor buttons and recipient corneas in lamellar and penetrating keratoplasty procedures, Dr Kymionis said. “The potential advantages of this technology in keratoplasty is the earlier wound healing, faster visual rehabilitation and the ability to customise the patterns of corneal transplantation according to the recipient disease.†In penetrating keratoplasty procedures, the precision side-cuts which the femtosecond laser provides can help reduce the amount of tissue removed from the recipient’s cornea. For example, using a “mushroom†side-cut profile in eyes with anterior corneal scarring will preserve more of the recipient’s endothelium, and using the “top hat†side-cut profile in eyes with endothelial disease will preserve more of the recipient’s stroma. In a separate presentation by Dr Kymionis, a case study was presented which showed how the femtosecond laser can be used to help improve the delivery of antimicrobial agents to diseased corneas.

This case involved a 71-year-old woman who presented with red eye, mucopurulent discharge, photophobia, blurred vision and pain. She was referred because of recurrent episodes of keratitis and corneal abscess non-responsive to antibiotic therapy and surface keratectomy. Her corrected distant visual acuity in the affected eye was finger counting. Slit-lamp examination revealed corneal infiltrate, severe neovascularisation, corneal oedema with Descemet’s membrane folds and anterior chamber reaction. Dr Kymionis and his associates therefore decided to try using the femtosecond laser to create a channel through which to deliver antifungal therapy directly into the region of the corneal abscess. The investigators saw an improvement in the clinical condition of the eye at slit lamp examination by the fifth day of followup. At six months follow-up the patients’ eye remains in a stable condition with a corrected distance visual acuity of 20/100.